U.S. patent number RE41,533 [Application Number 11/493,943] was granted by the patent office on 2010-08-17 for image processing method, image processing apparatus and data recording medium.
This patent grant is currently assigned to Panasonic Corporation. Invention is credited to Choong Seng Boon, Shinya Kadono, Takahiro Nishi, Toshiya Takahashi.
United States Patent |
RE41,533 |
Nishi , et al. |
August 17, 2010 |
**Please see images for:
( Certificate of Correction ) ** |
Image processing method, image processing apparatus and data
recording medium
Abstract
An image processing method for dividing a digital image signal
into plural image signals corresponding to plural blocks
constituting a single display screen, and performing block-by-block
coding of the image signals of the respective blocks, comprises
transforming an image signal of a coding target block to be
subjected to coding into frequency components by frame-by-frame
frequency transformation on a frame basis or field-by-field
frequency transformation on a field basis; setting a processing
order for coding the frequency components corresponding to the
image signal of the coding target block, according as the image
signal of the coding target block has been subjected to the
frame-by-frame frequency transformation or the field-by-field
frequency transformation; and successively coding the frequency
components corresponding to the image signal of the coding target
block according to the order which has been set. Therefore, in
coding of an interlaced image or a specific progressive image in
which frame DCT blocks and field DCT blocks coexist, a run length
is increased, thereby improving coding efficiency.
Inventors: |
Nishi; Takahiro (Ikomashi,
JP), Takahashi; Toshiya (Ibarakishi, JP),
Boon; Choong Seng (Yokohamashi, JP), Kadono;
Shinya (Nishinomiyashi, JP) |
Assignee: |
Panasonic Corporation (Osaka,
JP)
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Family
ID: |
27318356 |
Appl.
No.: |
11/493,943 |
Filed: |
July 27, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10682849 |
Oct 10, 2003 |
Re. 39318 |
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Reissue of: |
09118991 |
Jul 20, 1998 |
06426975 |
Jul 30, 2002 |
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Foreign Application Priority Data
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Jul 25, 1997 [JP] |
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9-200499 |
Sep 18, 1997 [JP] |
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9-253765 |
May 22, 1998 [JP] |
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10-14919 |
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Current U.S.
Class: |
375/240.13;
375/E7.15; 375/E7.226 |
Current CPC
Class: |
H04N
19/129 (20141101); H04N 19/176 (20141101); H04N
19/105 (20141101); H04N 19/18 (20141101); H04N
19/60 (20141101); H04N 19/593 (20141101); H04N
19/16 (20141101); H04N 19/48 (20141101) |
Current International
Class: |
H04B
1/66 (20060101) |
Field of
Search: |
;375/240.21,240.13,240.07,240.01,240.02,240.15,240.16,240.17,240.2,240.28,240.29
;382/233,232,234,230 ;348/459,405.1,423,406.1,426,409.1,845,416.1
;345/58 ;708/402 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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5-95542 |
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Apr 1993 |
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JP |
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6-86264 |
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Mar 1994 |
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JP |
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6-125278 |
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May 1994 |
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JP |
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6-165163 |
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Jun 1994 |
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JP |
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6-245200 |
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JP |
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6-245203 |
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Sep 1994 |
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JP |
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7-162859 |
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Jun 1995 |
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JP |
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8-37640 |
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Feb 1996 |
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JP |
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8-79766 |
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Mar 1996 |
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JP |
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09-187004 |
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Jul 1997 |
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JP |
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0197001 |
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Aug 2008 |
|
JP |
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Other References
Atul Puri et al, "Adaptive Frame/Field Motion Compensated Video
Coding," Signal Processing Image Communication, Elsevier Science
Publishers B.V., Amsterdam, NL., Feb. 1993, vol. 5, No. 1/2, pp.
39-58. cited by other .
M. Zhou et al, "MPEG-2 Video Coding with an Adaptive Selection of
Scanning Path and Picture Structure," Proceedings of the Spie,
Spie, Bellingham, VA, vol. 2952, Oct. 1996, pp. 472-480. cited by
other .
Eisuke Nakasu et al, "Intra/Inter Mode Adaptive DCT Coding System
of HDTV Signals," Signal Processing of HDTV, III, 1992 Elsevier
Science Publishers B.V., Workshop 4, Sep. 1991, pp. 439-446. cited
by other .
Lee, Jong Hwa et al, "An Efficient Encoding of DCT Blocks with
Block-Adapative Scanning," IEICE Trans Commun., vol. E77-B, No. 12,
pp. 1489-1494, Dec. 1994. cited by other .
Puri, A. et al, "Improvements in DCT Based Video Coding," SPIE,
vol. 3024, 0277-786X/97, pp. 676-688, 1997. cited by other.
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Primary Examiner: Vo; Tung
Attorney, Agent or Firm: Steptoe & Johnson LLP
Parent Case Text
.Iadd.Notice: More than one reissue application has been filed for
the reissue of U.S. Pat. No. 6,426,975. The resissue applications
are Ser. No. 10/682,849, filed Oct. 10, 2003, now U.S. Reissue Pat.
No. RE 39,318, and the present application, which is a divisional
reissue of U.S. Pat. No. 6,426,975..Iaddend.
Claims
What is claimed is:
1. An image processing method for performing block-by-block
decoding of a coded image signal that is obtained by performing a
coding process including frequency transformation to a digital
image signal, for each of blocks constituting a single display
screen, said method comprising: performing rearrangement to an
input signal of a decoding target block to be subjected to decoding
that is obtained by coding various frequency components which have
been subjected to an inter-frame prediction process and an
intra-frame prediction process in a prescribed order, with
switching, on the basis of flag information indicating switching of
rearrangement, which information is input together with the input
signal, between the first rearrangement operation in which the
input signal is subjected to adaptive rearrangement in an order
according to the kinds of both the prediction processes, and the
second rearrangement operation in which the input signal is
subjected to rearrangement in a specific order, regardless of the
kinds of both the prediction processes; generating intra-frame
predicted values of frequency components corresponding to the
decoding target block from frequency components corresponding to an
already decoded block located in the vicinity of the decoding
target block, by the intra-frame prediction process; generating
frequency components corresponding to the decoding target block on
the basis of the input signal after the rearrangement and the
intra-frame predicted values; performing inverse frequency
transformation to the frequency components corresponding to the
decoding target block to generate one of an image signal
corresponding to the decoding target block and a difference signal
corresponding to the same block; and adding, to the difference
signal corresponding to the decoding target block, inter-frame
predicted values of an image signal of the decoding target block,
which are generated from an image signal corresponding to an
already decoded display screen different from a display screen
including the decoding target block by the inter-frame prediction
process, thereby generating an image signal corresponding to the
decoding target block.
2. The image processing method as defined in claim 1 wherein: a
coded interlaced image signal, which is obtained by coding an
interlaced image signal block by block, is received as the coded
image signal to be subjected to decoding; in the first
rearrangement operation, concerning an inter-coded block in which
frequency components obtained by frequency transformation of the
interlaced image signal correspond to inter-frame difference values
of a coding target block, the frequency components to which the
processing order from the side of low-frequency components toward
the side of high-frequency components has been uniformly set so
that the components arranged along a horizontal direction of a
display screen and the components arranged along a vertical
direction have uniform priorities, are rearranged according to the
processing order which has been uniformly set; and concerning an
intra-coded block in which frequency components obtained by
frequency transformation of the interlaced image signal correspond
to an image signal of a coding target block, the frequency
components to which the processing order from the side of
low-frequency components toward the side of high-frequency
components has been adaptively set according to the kind of the
intra-frame prediction process, are rearranged according to the
processing order which has been adaptively set; and in the second
rearrangement operation, concerning both the inter-coded block and
intra-coded block, the frequency components to which the processing
order from the side of low-frequency components toward the side of
high-frequency components has been set so that the components
arranged along a vertical direction of a display screen have
priority over the components arranged along a horizontal direction,
are rearranged according to the processing order which has been set
with a priority given to a vertical direction.
3. A data recording medium containing an image processing program,
which makes a computer execute image processing in the image
processing method defined in claim 1.
4. An image processing apparatus for performing block-by-block
decoding of a coded image signal that is obtained by performing a
coding process including frequency transformation to a digital
image signal, for each of blocks constituting a single display
screen, said apparatus comprising: a variable-length decoding unit
for performing variable-length decoding to a coded string that is
obtained by performing inter-frame prediction, intra-frame
prediction, frequency transformation, quantization, rearrangement,
and variable-length coding to an image signal corresponding to each
block; inverse scanning means including plural inverse scanners
having different orders of rearrangement, and each rearranging
quantized values which have been rearranged in coding so that the
order of the quantized values is returned to the order before the
rearrangement, the inverse scanning means selecting an inverse
scanner to be used for rearranging the quantized values, according
to a scan changing signal which is generated outside/inside a
system, and inter-frame prediction information indicating the kind
of inter-frame prediction and intra-frame prediction information
indicating the kind of intra-frame prediction in coding;
intra-frame prediction means for generating intra-frame predicted
values of quantized values corresponding to a decoding target block
from quantized values corresponding to an already decoded block
located in the vicinity of the decoding target block, according to
the intra-frame prediction information, and outputting the result
of addition between the output of the inverse scanning means and
the intra-frame predicted values; inter-frame prediction means for
performing inter-frame prediction to the output of the intra-frame
prediction means on the basis of the inter-frame prediction
information, to generate an image signal corresponding to each
block; and an inverse blocking unit for inverse-blocking the image
signals of the respective blocks according to frequency
transformation type information indicating a processing unit of
frequency transformation in coding, to output a digital image
signal; and said inverse scanning means being constructed so that
switching is performed, on the basis of flag information indicating
switching of rearrangement, which information is input together
with an input signal of the decoding target block that is obtained
by coding various frequency components which have been subjected to
the inter-frame prediction process and the intra-frame prediction
process in a prescribed order, between the first rearrangement
operation in which the input signal is subjected to adaptive
rearrangement in an order according to the kinds of both the
prediction processes, and the second rearrangement operation in
which the input signal is subjected to rearrangement in a specific
order, regardless of the kinds of both the prediction
processes.
5. The image processing apparatus as defined in claim 4 wherein
said intra-frame prediction means comprises: an intra-frame
predictor for generating intra-frame predicted values of quantized
values corresponding to a decoding target block from quantized
values corresponding to an already decoded block located in the
vicinity of the decoding target block, according to intra-frame
prediction information; and a first adder for adding the
intra-frame predicted values to the output of the selected inverse
scanner; and said inter-frame prediction means comprises: an
inverse quantization unit for inverse-quantizing the output of the
first adder to output frequency components of a difference signal
corresponding to each block; an inverse frequency transformation
unit for performing inverse frequency transformation to the
frequency components to output a difference signal corresponding to
each block; a second adder for adding inter-frame predicted values
of an image signal corresponding to each block to the difference
signal to output an image signal corresponding to each block; a
frame memory for storing the output of the second adder, as an
image signal of an already decoded block as a constituent of an
already decoded display screen; and an inter-frame predictor for
generating the inter-frame predicted values on the basis of
inter-frame prediction information and an image signal of an
already coded block.
.Iadd.6. A method for coding a digital image signal on a block
basis, said method comprising: generating with a predicting unit a
predicted value for a frequency component of a coding target block
from a frequency component of an already coded block located in a
vicinity of the coding target block; generating with an adding unit
a difference by using the frequency component of the coding target
block and the predicted value; selecting with a selecting unit one
order setting operation from a first order setting operation in
which a processing order for frequency components of the coding
target block is adaptively set, and a second order setting
operation in which a specific processing order for frequency
components of the coding target block is set, on a basis of
processing order setting information; coding with a coding unit the
difference of the coding target block, based on the selected one
order setting operation into a coded difference; and outputting
with an outputting unit the coded difference together with the
processing order setting information..Iaddend.
.Iadd.7. The method of claim 6, wherein the processing order
setting information is a flag..Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates to image processing methods, image
processing apparatuses, and data recording media and, more
particularly, to image processing methods, image processing
apparatuses, and data recording media in which, in variable-length
coding of frequency components of an interlaced image signal, a
sequence of the frequency components is adaptively rearranged,
thereby improving coding efficiency.
BACKGROUND OF THE INVENTION
In recent years, discrete cosine transformation (DCT) has been
widely utilized in image coding processing. In MPEG as a
representative image coding method, an input image signal is
divided correspondingly to plural rectangular blocks constituting a
single display screen as units of DCT processing, and DCT
processing is performed block by block to the blocked image
signal.
A specific description is given of image coding in MPEG.
FIG. 26 is a block diagram illustrating a construction of a
conventional image processing apparatus which performs the
above-mentioned image coding. In FIG. 26, reference numeral 200a
designates a conventional image processing apparatus (image coding
apparatus), which performs coding including DCT processing to an
image signal. This image coding apparatus 200a consists of a
blocking unit 102 for dividing an input image signal 101
correspondingly to plural blocks constituting a single display
screen to generate an image signal (plural pixel values) 103
corresponding to each block, a DCT unit 104 for performing DCT
processing to the image signal (pixel values) 103 to transform the
image signal (pixel values) 103 into frequency components (DCT
coefficients) 105, and a quantization unit 106 for quantizing the
output 105 of the DCT unit 104 to generate quantized values 107
corresponding to each block. Herein, the DCT unit 104 and the
quantization unit 106 constitute an information source coding unit
200a1.
Further, the image coding apparatus 200a consists of a scanner 109
for setting the processing order for coding the quantized values
107, and a variable-length coding unit (hereinafter referred to as
a VLC unit) 112 for performing variable-length coding to quantized
values 111 to which the processing order has been set, according to
the set order, to generate a bit stream 113 corresponding to the
image signal of each block.
A description is given of the operation.
Initially, the blocking unit 102 blocks an input image signal 101
correspondingly to rectangular blocks each comprising 8.times.8
pixels, and outputs an image signal (plural pixel values) 103
corresponding to each block. The DCT unit 104 transforms the image
signal (pixel values) 103 into plural frequency components (DCT
coefficients) 105 by DCT. The quantization unit 106 converts the
DCT coefficients 105 into quantized values 107 by quantization.
Then, the scanner 109 performs rearrangement of the quantized
values 107 so as to improve the efficiency of variable-length
coding. That is, the scanner 109 sets the processing order for
coding. Thereafter, the VLC unit 112 performs variable-length
coding to the quantized values which have been rearranged,
according to the set order. In addition, run length coding is used
in variable-length coding processing. Therefore, when a scan is
performed so that coefficients of about the same size are
consecutive, the efficiency of variable-length coding is
improved.
In coding an interlaced image signal, when correlations between
adjacent scan lines are strong, frame DCT processing, i.e., DCT
using a frame as a unit, is carried out. When correlations between
scan lines in a field are strong, field DCT processing, i.e., DCT
using a field as a unit, is carried out.
More specifically, as shown in FIG. 27, in frame DCT processing of
an interlaced image signal, scan lines of a first field and scan
lines of a second field are alternately arranged to form one
frame-screen. This frame screen is divided into plural macroblocks
each comprising 16.times.16 pixels. Each macroblock is divided into
four subblocks-each comprising 8.times.8 pixels. Thereby, the image
signal is subjected to DCT processing subblock by subblock.
Meanwhile, in field DCT processing of an interlaced image signal,
Each of macroblocks constituting one frame screen is formed by two
first subblocks comprising only scan lines of a first field and two
second subblocks comprising only scan lines of a second field.
Thereby, the image signal is subjected to DCT processing subblock
by subblock.
In MPEG, frame DCT or field DCT is adaptively selected for each
macroblock. Accordingly, in order to perform accurate decoding to
an input image signal, the blocking unit 102 in the image coding
apparatus 200a outputs DCT processing information 114 indicating a
unit of DCT processing for each macroblock (that is, information
indicating whether each macroblock has been subjected to frame DCT
or field DCT), together with the blocked image signal. Since a
subblock which has been subjected to field DCT (a field DCT block)
comprises only odd scan lines or only even scan lines among scan
lines constituting one frame screen, a DCT coefficient group
corresponding to the field DCT block includes more DCT coefficients
indicating that the rate of change of pixel values in a vertical
direction of a display screen is higher, as compared with a DCT
coefficient group corresponding to a subblock which has been
subjected to frame DCT (a field DCT block).
FIG. 28 is a block diagram illustrating a construction of an image
decoding apparatus corresponding to the image coding apparatus
shown in FIG. 26. In FIG. 28, reference numeral 200b designates an
image processing apparatus (image decoding apparatus), which
decodes the coded image signal 113 which has been coded by the
image coding apparatus 200a. This image decoding apparatus 200b
consists of a variable-length decoding unit (hereinafter referred
to as a VLD unit) 201 for performing variable-length decoding to
the coded image signal 113, and an inverse scanner 202 for
performing an inverse scan to quantized values 111 which are
obtained by decoding so that the order of the quantized values 111
is returned to the order before rearrangement in coding. Further,
the image decoding apparatus 200b consists of an inverse
quantization unit 203 for inverse-quantizing quantized values 107
which have been subjected to inverse scanning, to generate DCT
coefficients (frequency components) 105 corresponding to a decoding
target block to be subjected to decoding, an inverse DCT unit 204
for performing inverse DCT processing to the DCT coefficients 105
to generate an image signal (pixel values) 103 corresponding to the
decoding target block, and an inverse blocking unit 205 for
inverse-blocking the image signals 103 on the basis of the DCT
processing information 114 from the image coding apparatus 200a,
thereby regenerating an image signal 101 corresponding to one frame
screen. Herein, the inverse quantization unit 203 and the inverse
DCT unit 204 constitute an information source decoding unit
200b1.
In the image decoding apparatus 200b, inverse converting processes
corresponding to the respective converting processes in the image
coding apparatus 200a are carried out to a coded image signal, in
the reverse order of the order in coding, thereby accurately
decoding the coded image signal.
FIG. 29 is a block diagram illustrating a construction of another
conventional image coding apparatus.
In FIG. 29, reference numeral 200c designates an image processing
apparatus (image coding apparatus), which performs intra-frame
predictive coding processing comprising generating predicted values
of quantized values of a coding target block using information in a
frame, and coding difference values between the predicted values
and the quantized values of the coding target block.
This image coding apparatus 200c includes the image coding
apparatus 200a, a prediction unit 200c2 for generating predicted
values, and a scanning unit 200c1 for changing a scan method using
a parameter concerning generation of the predicted values. The
prediction unit 200c2 consists of a predictor 305 for generating
predicted values 303, and outputting first prediction information
309a and second prediction information 309b concerning generation
of the predicted values, an adder 301 for subtracting the output
(predicted values) 303 of the predictor 305 from the output 107 of
the quantization unit 106, and an adder 304 for adding the output
303 of the predictor 305 to an output 302 of the adder 301.
The scanning unit 200c1 consists of three scanners
109s1.about.109s3 having different scan methods, for scanning the
output 302 of the prediction unit 200c2, a first switch 108c for
selecting one of the three scanners on the basis of a control
signal 116 and supplying the output 302 of the prediction unit
200c2 to the selected scanner, a second switch 110c for selecting
one of the three scanners on the basis of the control signal 116
and supplying an output of the selected scanner to the VLC unit
112, and a scan control unit 1401c for generating the control
signal 116 on the basis of the first prediction information 309a.
In addition, the second prediction information 309b is output from
the image coding apparatus 200c.
In the image coding apparatus 200c thus constructed, a scan method
is changed using the parameter concerning generation of predicted
values (prediction information) 309, whereby the efficiency of
variable-length coding is enhanced.
A description is given of a method for generating predicted values
with reference to FIG. 30.
FIG. 30 shows a macroblock comprising 16.times.16 pixels. This
macroblock comprises four subblocks (hereinafter simply referred to
as blocks) R0, R1, R2 and X each comprising 8.times.8 pixels. The
block X is a coding target block, and the blocks R0, R1 and R2 are
already coded blocks which are adjacent to the coding target block
X. Either block R1 or block R2 is referred in generating predicted
values (quantized values) of the coding target block X. The block
to be referred is decided using DC coefficients of the blocks R0,
R1 and R2 (quantized values at the left upper ends of these
blocks). Specifically, the absolute value of the difference between
the DC coefficients of the blocks R0 and R1 is compared with the
absolute value of the difference between the DC coefficients of the
blocks R0 and R2. When the absolute value of the difference between
the DC coefficients of the blocks R0 and R1 is larger, the block R1
is referred (reference in a vertical direction). When it is
smaller, the block R2 is referred (reference in a horizontal
direction).
When the block R1 is referred, the DC coefficient (the quantized
value at the left upper end) of the block R1 and AC coefficients
(quantized values at the uppermost line, except the DC coefficient)
of the block R1 are used as predicted values of the coefficients of
the block X at the same positions. When the block R2 is referred,
the DC coefficient (the quantized value at the left upper end) of
the block R2 and AC coefficients (quantized values at the leftmost
line, except the DC coefficient) of the block R2 are used as
predicted values of the coefficients of the block X at the same
positions. In addition, in a case where the efficiency of
variable-length coding is degraded by predicting AC coefficients,
no AC prediction may be carried out.
A scan method is changed according to ON/OFF of Ac prediction
(whether AC prediction is performed or not) in intra-frame
prediction. Further, when AC prediction is in the ON state, a scan
method is changed according to a reference direction of prediction.
The first prediction information 309a supplied to the scan control
unit 1401c includes ON/OFF information indicating ON/OFF of AC
prediction, and prediction direction information indicating a
reference direction for AC prediction, and the second prediction
information 309b includes only the ON/OFF information of AC
prediction.
When Ac prediction is in the OFF state, a scan of quantized values
is executed in the order shown in FIG. 31(a). Thereby, the
processing order for coding is set to the quantized values. In this
case, in a group of quantized values corresponding to a subblock,
high-frequency components uniformly distribute in vertical and
horizontal directions very often. Therefore, the quantized values
are uniformly scanned in the order from low-frequency components to
high-frequency components. When AC prediction is performed and a
vertical direction is referred, a scan of quantized values is
executed in the order shown in FIG. 31(b). In this case, a group of
quantized values corresponding to a subblock has a distribution in
which high-frequency components in a horizontal direction are
reduced by the prediction. Therefore, the quantized values are
scanned with a priority given to a horizontal direction, thereby
improving the efficiency of variable-length coding. When AC
prediction is performed and a horizontal direction is referred, a
scan of quantized values is executed in the order shown in FIG.
31(c). In this case, a group of quantized values corresponding to a
subblock has a distribution in which high-frequency components in a
vertical direction are reduced by the prediction. Therefore, the
quantized values are scanned with a priority given to a vertical
direction, thereby improving the efficiency of variable-length
coding.
FIG. 32 is a block diagram illustrating a construction of an image
decoding apparatus corresponding to the image coding apparatus
shown in FIG. 29. In FIG. 32, reference numeral 200d designates an
image processing apparatus (image decoding apparatus), which
decodes the coded image signal 308 that has been coded in the image
coding apparatus 200c.
This image decoding apparatus 200d has an inverse scanning unit
200d1 for performing an inverse scan to quantized values which are
obtained by variable-length decoding of the coded image signal 308
so that the order of the quantized values is returned to the order
before scanning in coding, and changing an inverse scan method on
the basis of the prediction information (parameter) concerning
generation of predicted values in the image coding apparatus 200c,
and a prediction unit 200d2 for adding quantized values (predicted
values) of a decoding target block which are predicted from
quantized values of an already decoded block in the vicinity of the
decoding target block, to the quantized values corresponding to the
decoding target block which have been subjected to inverse
scanning.
The inverse scanning unit 200d1 consists of three inverse scanners
202s1.about.202s3 having different inverse scan methods, for
inverse-scanning the output of the VLD unit 201, a first switch
108d for selecting one of the three inverse scanners on the basis
of a control signal 116 and supplying the output of the VLD unit
201 to the selected inverse scanner, a second switch 110d for
selecting one of the three inverse scanners on the basis of the
control signal 116 and supplying the output of the selected inverse
scanner to the prediction unit 200d2, and an inverse scan control
unit 1401d for generating the control signal 116 on the basis of
the first prediction information 309a.
In addition, the inverse scanner 202s1 performs an inverse scan
corresponding to the scan by the scanner 109s1 in the image coding
apparatus 200c, the inverse scanner 202s2 performs an inverse scan
corresponding to the scan by the scanner 109s2 in the image coding
apparatus 200c, and the inverse scanner 202s3 performs an inverse
scan corresponding to the scan by the scanner 109s3 in the image
coding apparatus 200c.
The prediction unit 200d2 consists of a predictor 401 for
generating predicted values 303 on the basis of the second
prediction information 309b output from the image coding apparatus
200c and values 107d corresponding to the quantized values 107 in
the image coding apparatus 200c, and generating control prediction
information 309a' corresponding to the first prediction information
309a in the image coding apparatus 200c, and an adder 304 for
adding the predicted values 303 to the output 302 of the inverse
scanning unit 200d1. In addition, like the first prediction
information 309a, the control prediction information 309a' includes
ON/OFF information of AC prediction and prediction direction
information of AC prediction.
In the image decoding apparatus 200d thus constructed, inverse
converting processes corresponding to the respective converting
processes in the image coding apparatus 200c shown in FIG. 29 are
carried out to a coded image signal, in the reverse order of the
order in coding, thereby accurately decoding the coded image
signal.
FIG. 33 is a block diagram illustrating a construction of still
another conventional image coding apparatus. In FIG. 33, reference
numeral 200e designates an image processing apparatus (image coding
apparatus), which performs inter-frame predictive coding processing
comprising generating predicted values of an image signal (pixel
values) of a coding target frame from another frame, and coding
difference values between the image signal (pixel values) of the
coding target frame and the predicted values.
This image coding apparatus 200e has an information source coding
unit 200e2 for performing information source coding to difference
values 1002 between an image signal (pixel values) 103 obtained by
blocking and predicted values 1008 of the image signal 103, in
place of the information source coding unit 200a1 in the image
coding apparatus 200a shown in FIG. 26, which performs information
source coding to the image signal 103. Further, the image coding
apparatus 200e has a scanning unit 200e1 for changing a scan
method, i.e., the processing order for coding, according to a
parameter 1015 concerning generation of the predicted values 1008,
in place of the scanner 109 in the image coding apparatus 200a.
The information source coding unit 200e2 consists of an adder 1001,
a DCT unit 104e, a quantization unit 106e, an inverse quantization
unit 203e, an inverse DCT unit 204e, an adder 1010, a frame memory
1014, and a predictor 1012.
The adder 1001 is for subtracting predicted values 1008 from an
image signal (pixel values) 103 corresponding to a coding target
block. The DCT unit 104e is for transforming difference values 1002
between the image signal (pixel values) 103 and the predicted
values 1008 into frequency components (DCT coefficients) 1003 by
DCT. The quantization unit 106e is for quantizing the DCT
coefficients 1003 to generate quantized values 1004 corresponding
to the coding target block.
Further, the inverse quantization unit 203e is for
inverse-quantizing the quantized values 1004 output from the
quantization unit 106e to output DCT coefficients 1007
corresponding to the DCT coefficients 1003. The inverse DCT unit
204e is for performing inverse DCT to the DCT coefficients 1007 to
output difference signals 1009 corresponding to the difference
values 1002. The adder 1010 is for adding the predicted values 1008
to the difference signals 1009 to output an already coded image
signal 1011 corresponding to the coding target block.
Furthermore, the frame memory 1014 is for temporarily storing
already coded image signals 1011 corresponding to one frame or
corresponding to frames of a prescribed number. The predictor 1012
is for generating the predicted values 1008 on the basis of an
already coded image signal 1013 corresponding to a reference block
in the memory 1014 and the image signal 103 corresponding to the
coding target block.
The scanning unit 200e1 consists of two scanners 129s1 and 129s2
having different scan methods, for scanning the output of the
information source coding unit 200e2, a first switch 108e for
selecting one of the two scanners on the basis of a control signal
116e and supplying the output 1004 of the information source coding
unit 200e2 to the selected scanner, a second switch 110e for
selecting one of the two scanners on the basis of the control
signal 116e and supplying an output of the selected scanner to the
VLC unit 112, and a scan control unit 1016e for generating the
control signal 116e on the basis of a parameter 1015 from the
predictor 1012.
Herein, the scanner 129s1 performs a scan of quantized values in
the order shown in FIG. 31(a). The scanner 129s2 is constituted by
the respective elements 301, 304 and 305 in the prediction unit
200c2 shown in FIG. 29, and the respective elements 108c, 110c,
109s1.about.109s3 and 1401c in the scanning unit 200c1 shown in
FIG. 29. That is, the scanner 129s2 performs intra-frame prediction
to a block to which no inter-frame prediction has been performed in
coding (hereinafter referred to as an intra-coded block) and
selects one of the scanners 109s1.about.109s3 constituting the
scanner 129s2 on the basis of prediction information concerning
generation of predicted values. In addition, one of the scanners
109s1.about.109s3 constituting the scanner 129s2 performs a scan of
quantized values in the order shown in FIG. 31(a). The coding
processing by the image coding apparatus 200e is fundamentally
identical to that by the image coding apparatus 200c shown in FIG.
29, except that difference values between an image signal which is
obtained by blocking and predicted values of the image signal are
coded.
That is, in inter-frame predictive coding by the image coding
apparatus 200e, predicted values 1008 are set to 0 when prediction
efficiency is low, whereby an image signal 103 corresponding to a
coding target block is subjected to DCT processing as it is
(intra-coding). Switching between inter-coding and intra-coding is
performed for each macroblock, and information indicating either
inter-coding or intra-coding is added to a parameter 1015
concerning prediction.
Further, when a coding target block is an inter-coded macroblock,
the scanner 129s1 is selected. When the coding target block is an
intra-coded macroblock, the scanner 129s2 is selected. Thereby, a
scan method suitable for each coding is executed.
Specifically, quantized values corresponding to an intra-coded
macroblock are supplied to the scanner 129s2 comprising the
prediction unit 200c2 and the scanning unit 200c1 shown in FIG. 29.
In the scanner 129s2, predicted values of the quantized values are
generated by intra-frame prediction, and an adaptive scan is
performed to difference values between the quantized values of the
coding target block and the predicted values, on the basis of
prediction information concerning generation of the predicted
values.
Meanwhile, quantized values corresponding to an inter-coded
macroblock are supplied to the scanner 129s1, and a scan in the
order shown in FIG. 31(a) is performed in the scanner 129s1.
In the image coding apparatus 200e thus constructed, since the
difference values are coded, many DCT coefficients become 0 by
quantization, whereby the efficiency of variable-length coding is
improved.
In addition, in the image coding apparatus 200e, no intra-frame
prediction may be carried out to an intra-coded macroblock. In this
case, one of the scanners 109s1.about.109s3 constituting the
scanner 129s2 performs a scan in the order shown in FIG. 31(a) to
quantized values of the intra-coded macroblock.
FIG. 34 is a block diagram illustrating a construction of an image
decoding apparatus corresponding to the image coding apparatus 200e
shown in FIG. 33. In FIG. 34, reference numeral 200f designates an
image processing apparatus (image decoding apparatus), which
decodes the coded image signal 1006 that has been coded in the
image coding apparatus 200e.
This image decoding apparatus 200f has an inverse scanning unit
200f1 for performing an inverse scan to quantized values 1005 which
are obtained by variable-length decoding of the coded image signal
1006 so that the order of the quantized values is returned to the
order before scanning in coding, and changing an inverse scan
method on the basis of the parameter 1015 concerning generation of
predicted values in the image coding apparatus 200e, in place of
the inverse scanner 202 in the image decoding apparatus 200b shown
in FIG. 28. Further, the image decoding apparatus 200f has an
information source decoding unit 200f2 for performing information
source decoding to quantized values 1004 corresponding to a
decoding target block which have been subjected to inverse
scanning, in place of the information source de-coding unit 200b1
in the image decoding apparatus 200b.
The inverse scanning unit 200f1 consists of two inverse scanners
222s1 and 222s2 having different inverse scan methods, for
inverse-scanning the output 1005 of the VLD unit 201, a first
switch 108f for selecting one of the two inverse scanners on the
basis of a control signal 116f and supplying the output 1005 of the
VLD unit 201 to the selected inverse scanner, a second switch 110f
for selecting one of the two inverse scanners on the basis of the
control signal 116f and supplying the output of the selected
inverse scanner to the information source decoding unit 200f2, and
an inverse scan control unit 1016f for generating the control
signal 116f on the basis of the prediction parameter 1015. Herein,
the inverse scanners 222s1 and 222s2 correspond to the scanners
129s1 and 129s2 in the image coding apparatus 200e.
That is, the inverse scanner 222s1 performs an inverse scan
corresponding to a scan in the order shown in FIG. 31(a), and the
inverse scanner 222s2 is constituted by the respective elements
108d, 110d, 202s1.about.202s3 and 1401d in the inverse scanning
unit 200d1 shown in FIG. 32, and the respective elements 304 and
401 in the prediction unit 200d2 shown in FIG. 32.
The information source decoding unit 200f2 consists of an inverse
quantization unit 203f for inverse-quantizing the output 1004 of
the inverse scanning unit 200f1, an inverse DCT unit 204f for
performing inverse DCT processing to an output 1003 of the inverse
quantization unit 203f, an adder 1101f for adding predicted values
1008f of the decoding target block to an output 1002 of the inverse
DCT unit 204f.
Further, the information source decoding unit 200f2 consists of a
frame memory 1014f for temporarily storing already decoded image
signals 103 corresponding to one frame or frames of a prescribed
number, and a predictor 1102f for generating the predicted values
1008f of the decoding target block on the basis of an already
decoded image signal 1013f corresponding to a reference block in
the memory 1014f and the parameter 1015 concerning prediction in
coding.
In the image decoding apparatus 200f thus constructed, inverse
converting processes corresponding to the respective converting
processes in the image coding apparatus 200e shown in FIG. 33 are
carried out to a coded image signal, in the reverse order of the
order in coding, thereby accurately decoding the coded image
signal.
The scan changing method in any of the conventional image
processing apparatuses is available for progressive image coding in
which all blocks are frame DCT blocks. However, in interlaced image
coding in which frame DCT blocks and field DCT blocks coexist,
since a field DCT block and a frame DCT block have different
distributions of DCT coefficients, coefficients of about the same
size are not consecutive when the same scan changing method is
used, so that the efficiency of variable-length coding is
degraded.
That is, in interlaced image coding in which either frame DCT
processing or field DCT processing is adaptively selected for each
macroblock and macroblocks having different DCT types coexist, when
a scan method is changed using a parameter concerning generation of
predicted values, since a field DCT block and a frame DCT block
have different distributions of DCT coefficients, coefficients of
about the same size are not consecutive, so that the efficiency of
variable-length coding is degraded.
Further, also in inter-frame predictive coding of an interlaced
image in any of the conventional image processing apparatuses, the
above-mentioned problem arises because macroblocks having different
DCT types coexist.
Furthermore, also in coding of a progressive image, when switching
is performed between frame DCT processing and field DCT processing
according to the content of the image, for example, in a case where
frame DCT processing is executed when correlations between adjacent
scan lines are strong and field DCT processing is executed when
correlations between adjacent scan lines are weak, the efficiency
of variable-length coding is degraded as in the interlaced image
coding.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide image
processing apparatuses and image processing methods in which, in
coding of an interlaced image in which macroblocks having different
DCT types coexist, or in coding of a specific progressive image, a
scan method that improves the efficiency of variable-length coding
can be adaptively selected, thereby realizing highly efficient
coding.
Another object of the present invention is to provide data
recording media in which image processing programs for implementing
the above-mentioned image processing methods are recorded.
Other objects and advantages of the present invention will become
apparent from the detailed description given hereinafter; it should
be understood, however, that the detailed description and specific
embodiment are given by way of illustration only, since various
changes and modifications within the scope of the invention will
become apparent to those skilled in the art from this detailed
description.
According to a first aspect of the present invention, an image
processing method for dividing a digital image signal into plural
image signals corresponding to plural blocks constituting a single
display screen, and performing block-by-block coding of the image
signals of the respective blocks, comprises transforming an image
signal of a coding target block to be subjected to coding into
frequency components by one of frame-by-frame frequency
transformation on a frame basis and field-by-field frequency
transformation on a field basis; setting a processing order for
coding the frequency components corresponding to the image signal
of the coding target block, according as the image signal of the
coding target block has been subjected to the frame-by-frame
frequency transformation or the field-by-field frequency
transformation; and successively coding the frequency components
corresponding to the image signal of the coding target block
according to the order which has been set.
Thus, a processing order for coding is set to frequency components
corresponding to an image signal of a coding target block,
according as the image signal of the coding target block has been
subjected to frame-by-frame frequency transformation or
field-by-field frequency transformation. Therefore, in coding of an
interlaced image in which frame DCT blocks and field DCT blocks
coexist, a run length is increased, thereby improving coding
efficiency in the interlaced image coding. In addition, in coding
of a specific progressive image in which frame DCT blocks and field
DCT blocks coexist, the same effect is obtained.
According to a second aspect of the present invention, an image
processing method for performing block-by-block decoding of a coded
image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal that is obtained by
coding various frequency components in a prescribed order, in an
order which is decided according as an image signal corresponding
to a decoding target block to be subjected to decoding has been
subjected to frame-by-frame frequency transformation on a frame
basis or field-by-field frequency transformation on a field basis,
thereby generating frequency components corresponding to the
decoding target block; and performing inverse frequency
transformation to the frequency components corresponding to the
decoding target block to regenerate an image signal corresponding
to the decoding target block.
Thus, an input signal that is obtained by coding various frequency
components in a prescribed order is subjected to rearrangement in
an order which is decided according as an image signal
corresponding to a decoding target block to be subjected to
decoding has been subjected to frame-by-frame frequency
transformation on a frame basis or field-by-field frequency
transformation on a field basis, thereby generating frequency
components corresponding to the decoding target block. Therefore,
in variable-length decoding of DCT coefficients of either a
progressive image or an interlaced image, accurate and efficient
decoding can be carried out to a bit stream which has been coded
using an adaptive scan changing method, i.e., a method for
adaptively changing a processing order for coding, thereby
regenerating an image signal.
According to a third aspect of the present invention, an image
processing method for dividing a digital image signal into plural
image signals corresponding to plural blocks constituting a single
display screen, and performing block-by-block coding of the image
signals of the respective blocks, comprises transforming an image
signal of a coding target block to be subjected to coding into
frequency components by one of frame-by-frame frequency
transformation on a frame basis and field-by-field frequency
transformation on a field basis; setting a processing order for
coding the frequency components corresponding to the image signal
of the coding target block, according to a combination pattern of
the kind of frequency transformation to which the image signal of
the coding target block has been subjected and the kind of
frequency transformation to which an image signal of an already
coded block located in the vicinity of the coding target block has
been subjected; and successively coding the frequency components
corresponding to the image signal-of-the coding target block
according to the order which has been set.
Thus, a processing order for coding is set to frequency components
corresponding to an image signal of a coding target block,
according to a combination pattern of the kind of frequency
transformation to which the image signal of the coding target block
has been subjected and the kind of frequency transformation to
which an image signal of an already coded block located in the
vicinity of the coding target block has been subjected. Therefore,
scanning processing for setting a coding order is controlled more
finely and a more suitable scan is selected. Consequently, a run
length is more increased, resulting in further improved coding
efficiency.
According to a fourth aspect of the present invention, an image
processing method for performing block-by-block decoding of a coded
image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal that is obtained by
coding various frequency components in a prescribed order, in an
order which is decided according to a combination pattern of
frequency transformation to which an image signal corresponding to
a decoding target block to be subjected to decoding has been
subjected and frequency transformation to which an image signal
corresponding to an already decoded block located in the vicinity
of the decoding target block has been subjected, thereby generating
frequency components corresponding to the decoding target block;
and performing inverse frequency transformation to the frequency
components corresponding to the decoding target block to regenerate
an image signal corresponding to the decoding target block.
Thus, an input signal that is obtained by coding various frequency
components in a prescribed order is subjected to rearrangement in
an order which is decided according to a combination pattern of
frequency transformation to which an image signal corresponding to
a decoding target block to be subjected to decoding has been
subjected and frequency transformation to which an image signal
corresponding to an already decoded block located in the vicinity
of the decoding target block has been subjected, thereby generating
frequency components corresponding to the decoding target block.
Therefore, in variable-length decoding of DCT coefficients of
either a progressive image or an interlaced image, accurate and
efficient decoding can be carried out to a bit stream which has
been coded using an adaptive scan changing method, i.e., a method
for adaptively changing a processing order for coding, thereby
regenerating an image signal.
According to a fifth aspect of the present invention, an image
processing method for dividing a digital image signal into plural
image signals corresponding to plural blocks constituting a single
display screen, and performing block-by-block coding of the image
signals of the respective blocks, comprises transforming an image
signal of a coding target block to be subjected to coding into
frequency components by one of frame-by-frame frequency
transformation on a frame basis and field-by-field frequency
transformation on a field basis; generating predicted values of the
frequency components corresponding to the coding target block from
frequency components corresponding to an already coded block
located in the vicinity of the coding target block, by a prescribed
prediction process; setting a processing order for coding
difference values between the frequency components of the coding
target block and the predicted values, according to a combination
pattern of the kind of frequency transformation to which the image
signal of the coding target block has been subjected and the kind
of the prediction process; and successively coding the difference
values corresponding to the coding target block according to the
order which has been set.
Thus, a processing order for coding is set to difference values
between frequency components of a coding target block and predicted
values of the frequency components, according to a combination
pattern of the kind of frequency transformation to which an image
signal of the coding target block has been subjected and the kind
of a prediction process. Therefore, in coding of an interlaced
image in which frame DCT blocks and field DCT blocks coexist, a run
length is increased, thereby improving coding efficiency.
According to a sixth aspect of the present invention, an image
processing method for performing block-by-block decoding of a coded
image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal that is obtained by
coding various frequency components which have been subjected to a
prediction process in a prescribed order, in an order which is
decided according to a combination pattern of the kind of frequency
transformation to which an image signal corresponding to a decoding
target block to be subjected to decoding has been subjected and the
kind of the prediction process; generating predicted values of
frequency components corresponding to the decoding target block
from frequency-components corresponding to an already decoded block
located in the vicinity of the decoding target block, on the basis
of the kind of the prediction process; generating frequency
components corresponding to the decoding target block on the basis
of the input signal after the rearrangement and the predicted
values; and performing inverse frequency transformation to the
frequency components corresponding to the decoding target block to
regenerate an image signal corresponding to the decoding target
block.
Thus, an input signal that is obtained by coding various frequency
components which have been subjected to a prediction process in a
prescribed order is subjected to rearrangement in an order which is
decided according to a combination pattern of the kind of frequency
transformation to which an image signal corresponding to a decoding
target block to be subjected to decoding has been subjected and the
kind of the prediction process; and predicted values of frequency
components corresponding to the decoding target block are generated
from frequency components corresponding to an already decoded block
located in the vicinity of the decoding target block, on the basis
of the kind of the prediction process. Therefore, in
variable-length decoding of DCT coefficients of either a
progressive image or an interlaced image, accurate and efficient
decoding can be carried out to a bit stream which has been coded
using a fine and adaptive scan changing method, i.e., a method for
finely and adaptively changing a processing order for coding,
thereby regenerating an image signal.
According to a seventh aspect of the present invention, an image
processing method for dividing a digital image signal into plural
image signals corresponding to plural blocks constituting a single
display screen, and performing block-by-block coding of the image
signals of the respective blocks, comprises transforming an image
signal of a coding target block to be subjected to coding into
frequency components by one of frame-by-frame frequency
transformation on a frame basis and field-by-field frequency
transformation on a field basis; generating predicted values of the
frequency components corresponding to the coding target block from
frequency components corresponding to an already coded block
located in the vicinity of the coding target block, by a prescribed
prediction process; setting a processing order for coding
difference values between the frequency components of the coding
target block and the predicted values, according to a combination
pattern of the kind of frequency transformation to which the image
signal of the coding target block has been subjected, the kind of
frequency transformation to which an image signal of the already
coded block located in the vicinity of the coding target block has
been subjected, and the kind of the prediction process; and
successively coding the difference values corresponding to the
coding target block according to the order which has been set.
Thus, a processing order for coding is set to difference values
between frequency components of a coding target block and predicted
values of the frequency components, according to a combination
pattern of the kind of frequency transformation to which an image
signal of the coding target block has been subjected, the kind of
frequency transformation to which an image signal of an already
coded block located in the vicinity of the coding target block has
been subjected, and the kind of a prediction process. Therefore,
scanning processing for setting a coding order is controlled more
finely and a more suitable scan is selected. Consequently, a run
length is more increased, resulting in further improved coding
efficiency.
According to an eighth aspect of the present invention, an image
processing method for performing block-by-block decoding of a coded
image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal that is obtained by
coding various frequency components which have been subjected to a
prediction process in a prescribed order, in an order which is
decided according to a combination pattern of the kind of frequency
transformation to which an image signal corresponding to a decoding
target block to be subjected to decoding has been subjected, the
kind of frequency transformation to which an image signal
corresponding to an already decoded target block located in the
vicinity of the decoding target block has been subjected, and the
kind of the prediction process; generating predicted values of
frequency components corresponding to the decoding target block
from frequency components corresponding to the already decoded
block located in the vicinity of the decoding target block, on the
basis of the kind of the prediction process; generating frequency
components corresponding to the decoding target block on the basis
of the input signal after the rearrangement and the predicted
values; and performing inverse frequency transformation to the
frequency components corresponding to the decoding target block to
regenerate an image signal corresponding to the decoding target
block.
Thus, an input signal that is obtained by coding various frequency
components which have been subjected to a prediction process in a
prescribed order is subjected to rearrangement in an order which is
decided according to a combination pattern of the kind of frequency
transformation to which an image signal corresponding to a decoding
target block to be subjected to decoding has been subjected, the
kind of frequency transformation to which an image signal
corresponding to an already decoded block located in the vicinity
of the decoding target block has been subjected, and the kind of
the prediction process, and predicted values of frequency
components corresponding to the decoding target block are generated
from frequency components corresponding to the already decoded
block located in the vicinity of the decoding target block, on the
basis of the kind of the prediction process. Therefore, accurate
and efficient decoding can be carried out to a bit stream which has
been coded using a fine and adaptive scan changing method, i.e., a
method for finely and adaptively changing a processing order for
coding, thereby regenerating an image signal.
According to a ninth aspect of the present invention, an image
processing apparatus for dividing an input digital image signal
into plural image signals corresponding to plural blocks
constituting a single display screen, and performing block-by-block
coding of the image signals of the respective blocks, comprises a
blocking unit for blocking the digital image signal correspondingly
to the respective blocks, frame by frame or field by field, which
is used as a processing unit of frequency transformation, and
outputting the blocked image signal and frequency transformation
type information indicating the processing unit of frequency
transformation; a frequency transformation unit for performing
block-by-block frequency transformation to the blocked image signal
to output frequency components corresponding to the image signal of
each block; a quantization unit for quantizing the frequency
components to output quantized values corresponding to the image
signal of each block; plural scanners having different orders of
rearrangement, and each setting a prescribed processing order to
the quantized values by rearranging the quantized values; a scan
control unit for outputting a control signal for selecting a
scanner to be used for rearranging the quantized values, according
to the frequency transformation type information; and a
variable-length coding unit for performing variable-length coding
to the quantized values after the rearrangement.
Thus, a processing order for coding is set to frequency components
corresponding to an image signal of a coding target block,
according as the image signal of the coding target block has been
subjected to frame-by-frame frequency transformation or
field-by-field frequency transformation. Therefore, in coding of an
interlaced image in which frame DCT blocks and field DCT blocks
coexist, a run length is increased, thereby improving coding
efficiency in the interlaced image coding. In addition, in coding
of a specific progressive image in which frame DCT blocks and field
DCT blocks coexist, the same effect is obtained.
According to a tenth aspect of the present invention, an image
processing apparatus for performing block-by-block decoding of a
coded image signal that is obtained by performing a coding process
including frequency transformation on a frame basis or on a field
basis to a digital image signal, for each of blocks constituting a
single display screen, comprises a variable-length decoding unit
for performing variable-length decoding to a coded string that is
obtained by performing rearrangement and variable-length coding to
quantized values of frequency components of an image signal
corresponding to each block; plural inverse scanners having
different orders of rearrangement, and each rearranging quantized
values which have been rearranged in coding so that the order of
the quantized values is returned to the order before the
rearrangement, thereby outputting the quantized values; an inverse
scan control unit for outputting a control signal for selecting an
inverse scanner to be used for rearranging the quantized values,
according to frequency transformation type information indicating
whether frequency transformation in coding is performed on a frame
basis or on a field basis; an inverse quantization unit for
inverse-quantizing the quantized values to output frequency
components of an image signal corresponding to each block; an
inverse frequency transformation unit for performing inverse
frequency transformation to the frequency components to output an
image signal corresponding to each block; and an inverse blocking
unit for inverse-blocking the image signals of the respective
blocks according to the frequency transformation type information
to output a digital image signal.
Thus, an input signal that is obtained by coding various frequency
components in a prescribed order is subjected to rearrangement in
an order which is decided according as an image signal
corresponding to a decoding target block to be subjected to
decoding has been subjected to frame-by-frame frequency
transformation on a frame basis or field-by-field frequency
transformation on a field basis, thereby generating frequency
components corresponding to the decoding target block. Therefore,
in variable-length decoding of DCT coefficients of either a
progressive image or an interlaced image, accurate and efficient
decoding can be carried out to a bit stream which has been coded
using an adaptive scan changing method, i.e., a method for
adaptively changing a processing order for coding, thereby
regenerating an image signal.
According to an eleventh aspect of the present invention, an image
processing apparatus for dividing an input digital image signal
into plural image signals corresponding to plural blocks
constituting a single display screen, and performing block-by-block
coding of the image signals of the respective blocks, comprises a
blocking unit for blocking the digital image signal correspondingly
to the respective blocks, frame by frame or field by field, which
is used as a processing unit of frequency transformation, and
outputting the blocked image signal and frequency transformation
type information indicating the processing unit of frequency
transformation; a frequency transformation unit for performing
block-by-block frequency transformation to the blocked image signal
to output frequency components corresponding to the image signal of
each block; a quantization unit for quantizing the frequency
components to output quantized values corresponding to the image
signal of each block; a predictor for generating predicted values
of quantized values corresponding to a coding target block to be
subjected to coding, from quantized values corresponding to an
already coded block located in the vicinity of the coding target
block, and outputting the predicted values and prediction
information concerning the kind of the generating process of the
predicted values; a first adder for subtracting the predicted
values from the quantized values corresponding to the coding target
block to output difference values; a second adder for adding the
predicted values to the difference values to output the result of
the addition as quantized values corresponding to an already coded
block; plural scanners having different orders of rearrangement,
and each rearranging the difference values; a scan control unit for
outputting a control signal for selecting a scanner to be used for
rearranging the difference values, according to the prediction
information and the frequency transformation type information; and
a variable-length coding unit for performing variable-length coding
to the difference values after the rearrangement.
Thus, a processing order for coding is set to difference values
between frequency components of a coding target block and predicted
values of the frequency components, according to a combination
pattern of the kind of frequency transformation to which an image
signal of the coding target block has been subjected and the kind
of a prediction process. Therefore, in coding of an interlaced
image in which frame DCT blocks and field DCT blocks coexist, a run
length is increased, thereby improving coding efficiency.
According to a twelfth aspect of the present invention, an image
processing apparatus for performing block-by-block decoding of a
coded image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises a
variable-length decoding unit for performing variable-length
decoding to a coded string that is obtained by performing
prediction, rearrangement, and variable-length coding to quantized
values of frequency components of an image signal corresponding to
each block; plural inverse scanners having different orders of
rearrangement, and each rearranging quantized values which have
been rearranged in coding so that the order of the quantized values
is returned to the order before the rearrangement; an inverse scan
control unit for outputting a control signal for selecting an
inverse scanner to be used for rearranging the quantized values,
according to frequency transformation type information indicating
the kind of frequency transformation in coding and prediction
information indicating the kind of prediction in coding; an inverse
quantization unit for inverse-quantizing the quantized values to
output frequency components of an image signal corresponding to
each block; an inverse frequency transformation unit for performing
inverse frequency transformation to the frequency components to
output an image signal corresponding to each block; and an inverse
blocking unit for inverse-blocking the image signals of the
respective blocks according to the frequency transformation type
information to output a digital image signal.
Thus, an input signal that is obtained by coding various frequency
components which have been subjected to a prediction process in a
prescribed order is subjected to rearrangement in an order which is
decided according to a combination pattern of the kind of frequency
transformation to which an image signal corresponding to a decoding
target block to be subjected to decoding has been subjected and the
kind of the prediction process, and predicted values of frequency
components corresponding to the decoding target block are generated
from frequency components corresponding to an already decoded block
located in the vicinity of the decoding target block, on the basis
of the kind of the prediction process. Therefore, in
variable-length decoding of DCT coefficients of either a
progressive image or an interlaced image, accurate and efficient
decoding can be carried out to a bit stream which has been coded
using a fine and adaptive scan changing method, i.e., a method for
finely and adaptively changing a processing order for coding,
thereby regenerating an image signal.
According to a thirteenth aspect of the present invention, an image
processing method for dividing a digital image signal into plural
image signals corresponding to plural blocks constituting a single
display screen, and performing block-by-block coding of the image
signals of the respective blocks, comprises transforming an image
signal of a coding target block to be subjected to coding into
frequency components by one of frame-by-frame frequency
transformation on a frame basis and field-by-field frequency
transformation on a field basis; setting a processing order for
coding the frequency components corresponding to the image signal
of the coding target block, according to a distribution of
frequency components corresponding to an image signal of an already
coded block; and successively coding the frequency components
corresponding to the image signal of the coding target block
according to the order which has been set.
Thus, a processing order for coding is set to frequency components
corresponding to a coding target block, according to a processing
order for coding suitable for frequency components corresponding to
an already coded block. Therefore, in coding of an interlaced image
in which frame DCT blocks and field DCT blocks coexist, a run
length is increased, thereby improving coding efficiency. In
addition, in coding of a specific progressive image in which frame
DCT blocks and field DCT blocks coexist, the same effect is
obtained.
According to a fourteenth aspect of the present invention, an image
processing method for performing block-by-block decoding of a coded
image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal that is obtained by
coding various frequency components in a prescribed order, in an
order which is decided according to a distribution of frequency
components of an image signal corresponding to an already decoded
block; thereby generating frequency components corresponding to a
decoding target block to be subjected to decoding; and performing
inverse frequency transformation to the frequency components
corresponding to the decoding target block to regenerate an image
signal corresponding to the decoding target block.
Thus, an input signal that is obtained by coding various frequency
components in a prescribed order is subjected to rearrangement in
an order which is decided according to a processing order for
coding suitable for frequency components corresponding to an
already decoded block, thereby generating frequency components
corresponding to a decoding target block to be subjected to
decoding. Therefore, in variable-length decoding of DCT
coefficients of either a progressive image or an interlaced image,
accurate and efficient decoding can be carried out to a bit stream
which has been coded using a fine and adaptive scan changing
method, i.e., a method for finely and adaptively changing a
processing order for coding, thereby regenerating an image
signal.
According to a fifteenth aspect of the present invention, an image
processing method for dividing a digital image signal into plural
image signals corresponding to plural blocks constituting a single
display screen, and performing block-by-block coding of the image
signals of the respective blocks, comprises transforming an image
signal of a coding target block to be subjected to coding into
frequency components by one of frame-by-frame frequency
transformation on a frame basis and field-by-field frequency
transformation on a field basis; generating predicted values of the
frequency components corresponding to the coding target block from
frequency components corresponding to an already coded block
located in the vicinity of the coding target block, by a prescribed
prediction process; setting a processing order for coding
difference values between the frequency components of the coding
target block and the predicted values, with switching, on the basis
of flag information indicating whether adaptive order setting is
carried out or not, between the first order setting operation in
which a processing order is adaptively set according to the kind of
the prediction process, and the second order setting operation in
which a specific processing order is set regardless of the kind of
the prediction process; and successively coding the difference
values corresponding to the coding target block according to the
processing order which has been set, and transmitting/storing a
resulting coded signal, together with the flag information.
Thus, in coding, an adaptive scan is switched to OFF to execute a
specific scan suitable for an interlaced image or a specific
progressive image when required, whereby coding of an interlaced
image or a specific progressive image can be efficiently
simplified.
According to a sixteenth aspect of the present invention, an image
processing method for performing block-by-block decoding of a coded
image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal that is obtained by
coding various frequency components which have been subjected to a
prediction process in a prescribed order, with switching, on the
basis of flag information indicating whether adaptive rearrangement
is carried out or not, which information is input together with the
input signal, between the first rearrangement operation in which
the input signal is subjected to adaptive rearrangement in an order
according to the kind of the prediction process, and the second
rearrangement operation in which the input signal is subjected to
rearrangement in a specific order, regardless of the kind of the
prediction process; generating predicted values of frequency
components corresponding to a decoding target block to be subjected
to decoding from frequency components corresponding to an already
decoded block located in the vicinity of the decoding target block,
on the basis of the kind of the prediction process; generating
frequency components corresponding to the decoding target block on
the basis of the input signal after the rearrangement and the
predicted values; and performing inverse frequency transformation
to the frequency components corresponding to the decoding target
block to regenerate an image signal corresponding to the decoding
target block.
Thus, in decoding, an adaptive inverse scan is switched to OFF to
execute a specific inverse scan suitable for an interlaced image or
a specific progressive image when required, whereby accurate
decoding can be carried out to an interlaced image or a specific
progressive image which has been subjected to a specific scan by
switching an adaptive scan to OFF in coding.
According to a seventeenth aspect of the present invention, an
image processing method for dividing a digital image signal into
plural image signals corresponding to plural blocks constituting a
single display screen, and performing block-by-block coding of the
image signals of the respective blocks, comprises generating
predicted values of an image signal of a coding target block to be
subjected to coding from an image signal corresponding to an
already coded display screen different from a display screen
including the coding target block, by a prescribed prediction
process; transforming difference values between the image signal of
the coding target block and the predicted values into frequency
components by one of frame-by-frame frequency transformation on a
frame basis and field-by-field frequency transformation on a field
basis; setting a processing order for coding the frequency
components of the coding target block, with switching, on the basis
of flag information indicating whether adaptive order setting is
carried out or not, between the first order setting operation in
which a processing order is adaptively set according to the kind of
the prediction process, and the second order setting operation in
which a specific processing order is set regardless of the kind of
the prediction process; and successively coding the frequency
components corresponding to the coding target block according to
the processing order which has been set, and transmitting/storing a
resulting coded signal, together with the flag information.
Thus, in coding, since, for each of intra-coded macroblocks and
inter-coded macroblocks, one of plural scans is selected according
to a parameter concerning prediction and a scan switching signal, a
scan suitable for each coding method is performed. Therefore, in
inter coding of an interlaced image in which inter-coded
macroblocks and intra-coded macroblocks having different frequency
component distributions coexist, a run length is increased, thereby
improving coding efficiency. In addition, in inter coding of a
specific progressive image in which inter-coded macroblocks and
intra-coded macroblocks having different frequency component
distributions coexist, the same effect is obtained.
According to an eighteenth aspect of the present invention, an
image processing method for performing block-by-block decoding of a
coded image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal that is obtained by
coding various frequency components which have been subjected to a
prediction process in a prescribed order, with switching, on the
basis of flag information indicating whether adaptive rearrangement
is carried out or not, which information is input together with the
input signal, between the first rearrangement operation in which
the input signal is subjected to adaptive rearrangement in an order
according to the kind of the prediction process, and the second
rearrangement operation in which the input signal is subjected to
rearrangement in a specific order, regardless of the kind of the
prediction process; performing inverse frequency transformation to
the input signal after the rearrangement to generate a difference
signal corresponding to a decoding target block to be subjected to
decoding; generating predicted values of an image signal of the
decoding target block from an image signal corresponding to an
already decoded display screen different from a display screen
including the decoding target block, on the basis of the kind of
the prediction process; and regenerating an image signal
corresponding to the decoding target block on the basis of the
difference signal and the predicted values.
Thus, in decoding, for each of intra-coded macroblocks and
inter-coded macroblocks, one of plural inverse scans is selected
according to a parameter concerning prediction and a scan switching
signal. Therefore, accurate and efficient decoding can be carried
out to a bit stream which has been coded by selecting one of plural
scans for each of intra-coded macroblocks and inter-coded
macroblocks, according to the parameter concerning prediction and
the scan switching signal, thereby regenerating an image
signal.
According to a nineteenth aspect of the present invention, an image
processing apparatus for dividing an input digital image signal
into plural image signals corresponding to plural blocks
constituting a single display screen, and performing block-by-block
coding of the image signals of the respective blocks, comprises a
blocking unit for blocking the digital image signal correspondingly
to the respective blocks, frame by frame or field by field, which
is used as a processing unit of frequency transformation, and
outputting the blocked image signal and frequency transformation
type information indicating the processing unit of frequency
transformation; a frequency transformation unit for performing
block-by-block frequency transformation to the blocked image signal
to output frequency components corresponding to the image signal of
each block; a quantization unit for quantizing the frequency
components to output quantized values corresponding to the image
signal of each block; plural scanners having different orders of
rearrangement, and each setting a prescribed processing order to
the quantized values by rearranging the quantized values; a
characteristic analyzing unit for performing characteristic
analysis of the output of the quantization unit to output a scan
specifying signal for specifying a scanner which performs
rearrangement suitable for the quantized values of each block; a
memory for temporarily storing the scan specifying signals from the
characteristic analyzing unit; a scan control unit for outputting a
control signal for selecting a scanner to be used for rearranging
quantized values of a coding target block to be subjected to
coding, according to the scan specification signals which are
stored in the memory; and a variable-length coding unit for
performing variable-length coding to the quantized values after the
rearrangement.
Thus, a processing order for coding is set to frequency components
corresponding to a coding target block, according to a processing
order for coding suitable for frequency components corresponding to
an already coded block. Therefore, in coding of an interlaced image
in which frame DCT blocks and field DCT blocks coexist, a run
length is increased, thereby improving coding efficiency. In
addition, in coding of a specific progressive image in which frame
DCT blocks and field DCT blocks coexist, the same effect is
obtained.
According to a twentieth aspect of the present invention, an image
processing apparatus for performing block-by-block decoding of a
coded image signal that is obtained by performing a coding process
including frequency transformation on a frame basis or on a field
basis to a digital image signal, for each of blocks constituting a
single display screen, comprises a variable-length decoding unit
for performing variable-length decoding to a coded string that is
obtained by performing rearrangement and variable-length coding to
quantized values of frequency components of an image signal
corresponding to each block; plural inverse scanners having
different orders of rearrangement, and each rearranging quantized
values which have been rearranged in coding so that the order of
the quantized values is returned to the order before the
rearrangement; a characteristic analyzing unit for performing
characteristic analysis of the output of the inverse scanner to
output a scan specifying signal for specifying an inverse scanner
which performs rearrangement suitable for the quantized values of
each block; a memory for temporarily storing the scan specifying
signals from the characteristic analyzing unit; an inverse scan
control unit for outputting a control signal for selecting an
inverse scanner to be used for rearranging quantized values of a
decoding target block to be subjected to decoding, according to the
scan specification signals which are stored in the memory; an
inverse quantization unit for inverse-quantizing the quantized
values output from the selected inverse scanner to output frequency
components of an image signal corresponding to each block; an
inverse frequency transformation unit for performing inverse
frequency transformation to the frequency components to output an
image signal corresponding to each block; and an inverse blocking
unit for inverse-blocking the image signals of the respective
blocks according to frequency transformation type information
indicating whether frequency transformation in coding is performed
on a frame basis or on a field basis, to output a digital image
signal.
Thus, an input signal that is obtained by coding various frequency
components in a prescribed order is subjected to rearrangement in
an order which is decided according to a processing order for
coding suitable for frequency components corresponding to an
already decoded block, thereby generating frequency components
corresponding to a decoding target block to be subjected to
decoding. Therefore, in variable-length decoding of DCT
coefficients of either a progressive image or an interlaced image,
accurate and efficient decoding can be carried out to a bit stream
which has been coded using a fine and adaptive scan changing
method, i.e., a method for finely and adaptively changing a
processing order for coding, thereby regenerating an image
signal.
According to a twenty-first aspect of the present invention, an
image processing apparatus for dividing an input digital image
signal into plural image signals corresponding to plural blocks
constituting a single display screen, and performing block-by-block
coding of the image signals of the respective blocks, comprises a
blocking unit for blocking the digital image signal correspondingly
to the respective blocks, frame by frame or field by field, which
is used as a processing unit of frequency transformation, and
outputting the blocked image signal and frequency transformation
type information indicating the processing unit of frequency
transformation; a frequency transformation unit for performing
block-by-block frequency transformation to the blocked image signal
to output frequency components corresponding to the image signal of
each block; a quantization unit for quantizing the frequency
components to output quantized values corresponding to the image
signal of each block; a predictor for generating predicted values
of quantized values corresponding to a coding target block to be
subjected to coding, from quantized values corresponding to an
already coded block located in the vicinity of the coding target
block, and outputting the predicted values and prediction
information concerning the kind of the generating process of the
predicted values; a first adder for subtracting the predicted
values from the quantized values corresponding to the coding target
block to output difference values; a second adder for adding the
predicted values to the difference values to output the result of
the addition as quantized values corresponding to an already coded
block; plural scanners having different orders of rearrangement,
and each being selected by a selecting signal and rearranging the
difference values; a scan control unit for outputting a first
control signal for selecting a scanner to be used for rearranging
the difference values, according to the prediction information; a
switch for selecting one of the first control signal and a second
control signal for selecting a specific scan, according to a scan
changing signal which is generated outside/inside a system, and
outputting the selected control signal as the selecting signal of
the scanner, and a variable-length coding unit for performing
variable-length coding to the difference values after the
rearrangement.
Thus, in coding, an adaptive scan is switched to OFF to execute a
specific scan suitable for an interlaced image or a specific
progressive image when required, whereby coding of an interlaced
image or a specific progressive image can be efficiently
simplified.
According to a twenty-second aspect of the present invention, an
image processing apparatus for performing block-by-block decoding
of a coded image signal that is obtained by performing a coding
process including frequency transformation on a frame basis or on a
field basis to a digital image signal, for each of blocks
constituting a single display screen, comprises a variable-length
decoding unit for performing variable-length decoding to a coded
string that is obtained by performing prediction, rearrangement,
and variable-length coding to quantized values of frequency
components of an image signal corresponding to each block; plural
inverse scanners having different orders of rearrangement, and each
being selected by a selecting signal, and rearranging quantized
values which have been rearranged in coding so that the order of
the quantized values is returned to the order before the
rearrangement; an inverse scan control unit for outputting a first
control signal for selecting an inverse scanner to be used for
rearranging the quantized values, according to prediction
information indicating the kind of prediction in coding; a switch
for selecting one of the first control signal and a second control
signal for selecting a specific scan, according to a scan changing
signal, and outputting the selected control signal as the selecting
signal of the inverse scanner; a predictor for generating predicted
values of quantized values corresponding to a decoding target block
to be subjected to decoding, from quantized values corresponding to
an already decoded block located in the vicinity of the decoding
target block, according to the prediction information; an adder for
adding the predicted values to the output of the inverse scanner;
an inverse quantization unit for inverse-quantizing the output of
the adder to output frequency components of an image signal
corresponding to each block; an inverse frequency transformation
unit for performing inverse frequency transformation to the
frequency components to output an image signal corresponding to
each block; and an inverse blocking unit for inverse-blocking the
image signals of the respective blocks according to frequency
transformation type information indicating whether frequency
transformation in coding is performed on a frame basis or on a
field basis, to output a digital image signal.
Thus, in decoding, an adaptive inverse scan is switched to OFF to
execute a specific inverse scan suitable for an interlaced image or
a specific progressive image when required, whereby accurate
decoding can be carried out to an interlaced image or a specific
progressive image which has been subjected to a specific scan by
switching an adaptive scan to OFF in coding.
According to a twenty-third aspect of the present invention, an
image processing apparatus for dividing an input digital image
signal into plural image signals corresponding to plural blocks
constituting a single display screen, and performing block-by-block
coding of the image signals of the respective blocks, comprises a
blocking unit for blocking the digital image signal correspondingly
to the respective blocks, frame by frame or field by field, which
is used as a processing unit of frequency transformation, and
outputting the blocked image signal and frequency transformation
type information indicating the processing unit of frequency
transformation; a first adder for subtracting predicted values of
the blocked image signal from the blocked image signal to output a
difference signal; a frequency transformation unit for performing
block-by-block frequency transformation to the difference signal to
output frequency components corresponding to the difference signal
of each block; a quantization unit for quantizing the frequency
components to output quantized values corresponding to the image
signal of each block; an inverse quantization unit for
inverse-quantizing the quantized values to output the frequency
components corresponding to the difference signal of each block; an
inverse frequency transformation unit for performing inverse
frequency transformation to the output of the inverse quantization
unit to output the difference signal of each block; a second adder
for adding the predicted values to the output of the inverse
frequency transformation unit, and storing the result of the
addition in a frame memory, as an image signal of an already coded
block as a constituent of an already coded display screen; a
predictor for generating the predicted values on the basis of the
image signal of each block and an image signal of an already coded
block which is stored in the frame memory, and outputting the
predicted values and prediction information concerning the
generating process of the predicted values; plural scanners having
different orders of rearrangement, and each rearranging the
quantized values; a scan control unit for outputting a control
signal for selecting a scanner to be used for rearranging the
quantized values, according to a scan changing signal which is
generated outside/inside a system and the prediction information;
and a variable-length coding unit for performing variable-length
coding to the quantized values after the rearrangement.
Thus, in coding, since, for each of intra-coded macroblocks and
inter-coded macroblocks, one of plural scans is selected
according-to a parameter concerning prediction and a scan switching
signal, a scan suitable for each coding method is performed.
Therefore, in inter coding of an interlaced image in which
inter-coded macroblocks and intra-coded macroblocks having
different frequency component distributions coexist, a run length
is increased, thereby improving coding efficiency. In addition, in
inter coding of a specific progressive image in which inter-coded
macroblocks and intra-coded macroblocks having different frequency
component distributions coexist, the same effect is obtained.
According to a twenty-fourth aspect of the present invention, an
image processing apparatus for performing block-by-block decoding
of a coded image signal that is obtained by performing a coding
process including frequency transformation on a frame basis or on a
field basis to a digital image signal, for each of blocks
constituting a single display screen, comprises a variable-length
decoding unit for performing variable-length decoding to a coded
string that is obtained by performing prediction, frequency
transformation, quantization, rearrangement, and variable-length
coding to an image signal corresponding to each block; plural
inverse scanners having different orders of rearrangement, and each
rearranging quantized values which have been rearranged in coding
so that the order of the quantized values is returned to the order
before the rearrangement; an inverse scan control unit for
outputting a control signal for selecting an inverse scanner to be
used for rearranging the quantized values, according to a scan
changing signal and prediction information indicating the kind of
prediction in coding; an inverse quantization unit for
inverse-quantizing the output of the inverse scanner to output
frequency components of a difference signal corresponding to each
block; an inverse frequency transformation unit for performing
inverse frequency transformation to the frequency components to
output a difference signal corresponding to each block; an adder
for adding predicted values of an image signal corresponding to
each block to the difference signal to output an image signal
corresponding to each block; a frame memory for storing the output
of the adder, as an image signal of an already decoded block as a
constituent of an already decoded display screen; a predictor for
generating the predicted values on the basis of the prediction
information and an image signal of an already coded block; and an
inverse blocking unit for inverse-blocking the image signals of the
respective blocks according to frequency transformation type
information indicating whether frequency transformation in coding
is performed on a frame basis or on a field basis, to output a
digital image signal.
Thus, in decoding, for each of intra-coded macroblocks and
inter-coded macroblocks, one of plural inverse scans is selected
according to a parameter concerning prediction and a scan switching
signal. Therefore, accurate and efficient decoding can be carried
out to a bit stream which has been coded by selecting one of plural
scans for each of intra-coded macroblocks and inter-coded
macroblocks, according to the parameter concerning prediction and
the scan switching signal, thereby regenerating an image
signal.
According to a twenty-fifth aspect of the present invention, an
image processing method for dividing a digital image signal into
plural image signals corresponding to plural blocks constituting a
single display screen, and performing block-by-block coding of the
image signals of the respective blocks, comprises generating
inter-frame predicted values of an image signal of a coding target
block to be subjected to coding, from an image signal corresponding
to an already coded display screen different from a display screen
including the coding target block, by a prescribed inter-frame
prediction process; transforming one of inter-frame difference
values between the image signal of the coding target block and the
inter-frame predicted values, and the image signal of the coding
target block, into frequency components by one of frame-by-frame
frequency transformation on a frame basis and field-by-field
frequency transformation on a field basis; generating intra-frame
predicted values of the frequency components corresponding to the
coding target block from frequency components corresponding to an
already coded block located in the vicinity of the coding target
block, by a prescribed intra-frame prediction process; setting a
processing order for coding intra-frame difference values between
the frequency components of the coding target block and the
intra-frame predicted values, with switching, on the basis of flag
information indicating switching of order setting, between the
first order setting operation in which a processing order is
adaptively set according to the kinds of both the prediction
processes, and the second order setting operation in which a
specific processing order is set regardless of the kinds of both
the prediction processes; and successively coding the intra-frame
difference values corresponding to the coding target block
according to the processing order which has been set, and
transmitting/storing a resulting coded signal, together with the
flag information.
Thus, in coding, switching is performed, on the basis of flag
information indicating switching of order setting, between the
first order setting operation in which a processing order for
coding is adaptively set to intra-frame difference values between
frequency components of a coding target block and intra-frame
predicted values of the frequency components, according to the
kinds of inter-frame prediction and intra-frame prediction
processes, and the second order setting operation in which a
specific processing order for coding is set thereto, regardless of
the kinds of both the prediction processes. Therefore, in inter
coding of an interlaced image in which inter-coded macroblocks and
intra-coded macroblocks having different frequency component
distributions coexist, a run length is still more increased,
thereby improving coding efficiency. In addition, in inter coding
of a specific progressive image in which inter-coded macroblocks
and intra-coded macroblocks having different frequency component
distributions coexist, the same effect is obtained.
Specifically, in coding of an interlaced image signal, switching is
performed, according to a scan mode switching signal, between a
first coding mode in which an adaptive scan is performed to
quantized values of an intra-coded block and a zigzag scan is
performed to quantized values of an inter-coded block, and a second
coding mode in which a scan which gives a priority to a first
vertical direction is performed to the quantized values of the
intra-coded block and a scan which gives a priority to a second
vertical direction is performed to the quantized values of the
inter-coded block. Accordingly, in coding of an interlaced image
signal in which inter-coded blocks and intra-coded blocks having
different frequency component distributions coexist, coding
efficiency can be further improved.
According to a twenty-sixth aspect of the present invention, in the
image processing method as defined in the twenty-fifth aspect of
the invention, an interlaced image signal is received as the
digital image signal; in the first order setting operation,
concerning an inter-coded block in which the frequency components
obtained by the frequency transformation correspond to the
inter-frame difference values of the coding target block, the
processing order from the side of low-frequency components toward
the side of high-frequency components is set so that the components
arranged along a horizontal direction of a display screen and the
components arranged along a vertical direction have uniform
priorities; and concerning an intra-coded block in which the
frequency components obtained by the frequency transformation
correspond to the image signal of the coding target block, the
processing order from the side of low-frequency components toward
the side of high-frequency components is adaptively set according
to the kind of the intra-frame prediction process; and in the
second order setting operation, concerning both the inter-coded
block and intra-coded block, the processing order from the side of
low-frequency components toward the side of high-frequency
components is set so that the components arranged along a vertical
direction of a display screen have priority over the components
arranged along a horizontal direction.
Thus, in coding, switching is performed, on the basis of flag
information indicating switching of order setting, between the
first order setting operation in which a processing order for
coding is adaptively set to intra-frame difference values between
frequency components of a coding target block and intra-frame
predicted values of the frequency components, according to the
kinds of inter-frame prediction and intra-frame prediction
processes, and the second order setting operation in which a
specific processing order for coding is set thereto, regardless of
the kinds of both the prediction processes. Therefore, in inter
coding of an interlaced image in which inter-coded macroblocks and
intra-coded macroblocks having different frequency component
distributions coexist, a run length is still more increased,
thereby improving coding efficiency. In addition, in inter coding
of a specific progressive image in which inter-coded macroblocks
and intra-coded macroblocks having different frequency component
distributions coexist, the same effect is obtained.
According to a twenty-seventh aspect of the present invention, an
image processing method for performing block-by-block decoding of a
coded image signal that is obtained by performing a coding process
including frequency transformation to a digital image signal, for
each of blocks constituting a single display screen, comprises
performing rearrangement to an input signal of a decoding target
block to be subjected to decoding that is obtained by coding
various frequency components which have been subjected to an
inter-frame prediction process and an intra-frame prediction
process in a prescribed order, with switching, on the basis of flag
information indicating switching of rearrangement, which
information is input together with the input signal, between the
first rearrangement operation in which the input signal is
subjected to adaptive rearrangement in an order according to the
kinds of both the prediction processes, and the second
rearrangement operation in which the input signal is subjected to
rearrangement in a specific order, regardless of the kinds of both
the prediction processes; generating intra-frame predicted values
of frequency components corresponding to the decoding target block
from frequency components corresponding to an already decoded block
located in the vicinity of the decoding target block, by the
intra-frame prediction process; generating frequency components
corresponding to the decoding target block on the basis of the
input signal after the rearrangement and the intra-frame predicted
values; performing inverse frequency transformation to the
frequency components corresponding to the decoding target block to
generate one of an image signal corresponding to the decoding
target block and a difference signal corresponding to the same
block; and adding, to the difference signal corresponding to the
decoding target block, inter-frame predicted values of an image
signal of the decoding target block, which are generated from an
image signal corresponding to an already decoded display screen
different from a display screen including the decoding target block
by the inter-frame prediction process, thereby generating an image
signal corresponding to the decoding target block.
Thus, in decoding, switching is performed, on the basis of flag
information indicating switching of rearrangement, which
information is input together with an input signal of a decoding
target block to be subjected to decoding that is obtained by coding
various frequency components which have been subjected to an
inter-frame prediction process and an intra-frame prediction
process in a prescribed order, between the first rearrangement
operation in which the input signal is adaptively rearranged in an
order according to the kinds of both the prediction processes, and
the second rearrangement operation in which the input signal is
rearranged in a specific order, regardless of the kinds of both the
prediction processes. Therefore, accurate and efficient decoding
can be carried out to a bit stream which has been coded by
selecting one of plural scans for each of intra-coded macroblocks
and inter-coded macroblocks, according to a parameter concerning
prediction and a scan switching signal, thereby regenerating an
image signal.
According to a twenty-eighth aspect of the present invention, in
the image processing method as defined in the twenty-seventh aspect
of the invention, a coded interlaced image signal, which is
obtained by coding an interlaced image signal block by block, is
received as the coded image signal to be subjected to decoding; in
the first rearrangement operation, concerning an inter-coded block
in which frequency components obtained by frequency transformation
of the interlaced image signal correspond to inter-frame difference
values of a coding target block, the frequency components to which
the processing order from the side of low-frequency components
toward the side of high-frequency components has been uniformly set
so that the components arranged along a horizontal direction of a
display screen and the components arranged along a vertical
direction have uniform priorities, are rearranged according to the
processing order which has been uniformly set; and concerning an
intra-coded block in which frequency components obtained by
frequency transformation of the inter-laced image signal correspond
to an image signal of a coding target block, the frequency
components to which the processing order from the side of
low-frequency components toward the side of high-frequency
components has been adaptively set according to the kind of the
intra-frame prediction process, are rearranged according to the
processing order which has been adaptively set; and in the second
rearrangement operation, concerning both the inter-coded block and
intra-coded block, the frequency components to which the processing
order from the side of low-frequency components toward the side of
high-frequency components has been set so that the components
arranged along a vertical direction of a display screen have
priority over the components arranged along a horizontal direction,
are rearranged according to the processing order which has been set
with a priority given to a vertical direction.
Thus, in decoding, switching is performed, on the basis of flag
information indicating switching of rearrangement, which
information is input together with an input signal of a decoding
target block to be subjected to decoding that is obtained by coding
various frequency components which have been subjected to an
inter-frame prediction process and an intra-frame prediction
process in a prescribed order, between the first rearrangement
operation in which the input signal is adaptively rearranged in an
order according to the kinds of both the prediction processes, and
the second rearrangement operation in which the input signal is
rearranged in a specific order, regardless of the kinds of both the
prediction processes. Therefore, accurate and efficient decoding
can be carried out to a bit stream which has been coded by
selecting one of plural scans for each of intra-coded macroblocks
and inter-coded macroblocks, according to a parameter concerning
prediction and a scan switching signal, thereby regenerating an
image signal.
According to a twenty-ninth aspect of the present invention, an
image processing apparatus for dividing an input digital image
signal into plural image signals corresponding to plural blocks
constituting a single display screen, and performing block-by-block
coding of the image signals of the respective blocks, comprises a
blocking unit for blocking the digital image signal correspondingly
to the respective blocks, frame by frame or field by field, which
is used as a processing unit of frequency transformation, and
outputting the blocked image signal and frequency transformation
type information indicating the processing unit of frequency
transformation; inter-frame prediction means for performing
inter-frame prediction to the blocked image signal to output
inter-frame prediction data corresponding to inter-frame difference
values between the image signal of each block and inter-frame
predicted values of the image signal, and outputting inter-frame
prediction information concerning the generating process of the
inter-frame predicted values; intra-frame prediction means for
generating intra-frame predicted values of inter-frame prediction
data corresponding to a coding target block from inter-frame
prediction data corresponding to an already coded block located in
the vicinity of the coding target block, outputting intra-frame
difference values between the inter-frame prediction data and the
intra-frame predicted values, and outputting intra-frame prediction
information concerning the kind of the generating process of the
intra-frame predicted values; scanning means including plural
scanners having different orders of rearrangement, and each being
selected by a selecting signal and rearranging the intra-frame
difference values, the scanning means selecting a scanner to be
used for rearranging the intra-frame difference values, according
to the inter-frame prediction information and a scan changing
signal which is generated outside/inside a system; and a
variable-length coding unit for performing variable-length coding
to the intra-frame difference values after the rearrangement; and
said scanning means being constructed so that switching is
performed, on the basis of the scan changing signal, between the
first order setting operation in which a coding order is adaptively
set to the intra-frame difference values corresponding to the
coding target block, according to the kinds of both the prediction
processes, and the second order setting operation in which a
specific coding order is set thereto, regardless of the kinds of
both the prediction processes.
Thus, in coding, switching is performed, on the basis of flag
information indicating switching of order setting, between the
first order setting operation in which a processing order for
coding is adaptively set to intra-frame difference values between
frequency components of a coding target block and intra-frame
predicted values of the frequency components, according to the
kinds of inter-frame prediction and intra-frame prediction
processes, and the second order setting operation in which a
specific processing order for coding is set thereto, regardless of
the kinds of both the prediction processes. Therefore, in inter
coding of an interlaced image in which inter-coded macroblocks and
intra-coded macroblocks having different frequency component
distributions coexist, a run length is still more increased,
thereby improving coding efficiency. In addition, in inter coding
of a specific progressive image in which inter-coded macroblocks
and intra-coded macroblocks having different frequency component
distributions coexist, the same effect is obtained.
According to a thirtieth aspect of the present invention, in the
image processing apparatus as defined in the twenty-ninth aspect of
the invention, said inter-frame prediction means comprises a first
adder for subtracting inter-frame predicted values of the blocked
image signal from the blocked image signal to output a difference
signal; a frequency transformation unit for performing
block-by-block frequency transformation to the difference signal to
output frequency components corresponding to the difference signal
of each block; a quantization unit for quantizing the frequency
components to output quantized values corresponding to the
difference signal of each block as the inter-frame prediction data;
an inverse quantization unit for inverse-quantizing the quantized
values to output the frequency components corresponding to the
difference signal of each block; an inverse frequency
transformation unit for performing inverse frequency transformation
to the output of the inverse quantization unit to output the
difference signal of each block; a second adder for adding the
inter-frame predicted values to the output of the inverse frequency
transformation unit, and storing the result of the addition in a
frame memory, as an image signal of an already coded block as a
constituent of an already coded display screen; and an inter-frame
predictor for generating the inter-frame predicted values on the
basis of the image signal of each block and an image signal of an
already coded block which is stored in the frame memory, and
outputting the inter-frame predicted values and inter-frame
prediction information concerning the generating process of the
inter-frame predicted values; and said intra-frame prediction means
comprises an intra-frame predictor for generating intra-frame
predicted values of quantized values corresponding to a coding
target block from quantized values corresponding to an already
coded block located in the vicinity of the coding target block, and
outputting the intra-frame predicted values and intra-frame
prediction information concerning the kind of the generating
process of the intra-frame predicted values; a third adder for
subtracting the intra-frame predicted values from the quantized
values corresponding to the coding target block to output
intra-frame difference values; and a fourth adder for adding the
intra-frame predicted values to the difference values to output the
result of the addition as quantized values corresponding to an
already coded block.
Thus, in coding, switching is performed, on the basis of flag
information indicating switching of order setting, between the
first order setting operation in which a processing order for
coding is adaptively set to intra-frame difference values between
frequency components of a coding target block and intra-frame
predicted values of the frequency components, according to the
kinds of inter-frame prediction and intra-frame prediction
processes, and the second order setting operation in which a
specific processing order for coding is set thereto, regardless of
the kinds of both the prediction processes. Therefore, in inter
coding of an interlaced image in which inter-coded macroblocks and
intra-coded macroblocks having different frequency component
distributions coexist, a run length is still more increased,
thereby improving coding efficiency. In addition, in inter coding
of a specific progressive image in which inter-coded macroblocks
and intra-coded macroblocks having different frequency component
distributions coexist, the same effect is obtained.
According to a thirty-first aspect of the present invention, an
image processing apparatus for performing block-by-block decoding
of a coded image signal that is obtained by performing a coding
process including frequency transformation to a digital image
signal, for each of blocks constituting a single display screen,
comprises a variable-length decoding unit for performing
variable-length decoding to a coded string that is obtained by
performing inter-frame prediction, intra-frame prediction,
frequency transformation, quantization, rearrangement, and
variable-length coding to an image signal corresponding to each
block; inverse scanning means including plural inverse scanners
having different orders of rearrangement, and each rearranging
quantized values which have been rearranged in coding so that the
order of the quantized values is returned to the order before the
rearrangement, the inverse scanning means selecting an inverse
scanner to be used for rearranging the quantized values, according
to a scan changing signal which is generated outside/inside a
system, and inter-frame prediction information indicating the kind
of inter-frame prediction and intra-frame prediction information
indicating the kind of intra-frame prediction in coding;
intra-frame prediction means for generating intra-frame predicted
values of quantized values corresponding to a decoding target block
from quantized values corresponding to an already decoded block
located in the vicinity of the decoding target block, according to
the intra-frame prediction information, and outputting the result
of addition between the output of the inverse scanning means and
the intra-frame predicted values; inter-frame prediction means for
performing inter-frame prediction to the output of the intra-frame
prediction means on the basis of the inter-frame prediction
information, to generate an image signal corresponding to each
block; and an inverse blocking unit for inverse-blocking the image
signals of the respective blocks according to frequency
transformation type information indicating a processing unit of
frequency transformation in coding, to output a digital image
signal; and said inverse scanning means being constructed so that
switching is performed, on the basis of flag information indicating
switching of rearrangement, which information is input together
with an input signal of the decoding target block that is obtained
by coding various frequency components which have been subjected to
the inter-frame prediction process and the intra-frame prediction
process in a prescribed order, between the first rearrangement
operation in which the input signal is subjected to adaptive
rearrangement in an order according to the kinds of both the
prediction processes, and the second rearrangement operation in
which the input signal is subjected to rearrangement in a specific
order, regardless of the kinds of both the prediction
processes.
Thus, in decoding, switching is performed, on the basis of flag
information indicating switching of rearrangement, which
information is input together with an input signal of a decoding
target block to be subjected to decoding that is obtained by coding
various frequency components which have been subjected to an
inter-frame prediction process and an intra-frame prediction
process in a prescribed order, between the first rearrangement
operation in which the input signal is adaptively rearranged in an
order according to the kinds of both the prediction processes, and
the second rearrangement operation in which the input signal is
rearranged in a specific order, regardless of the kinds of both the
prediction processes. Therefore, accurate and efficient decoding
can be carried out to a bit stream which has been coded by
selecting one of plural scans for each of intra-coded macroblocks
and inter-coded macroblocks, according to a parameter concerning
prediction and a scan switching signal, thereby regenerating an
image signal.
According to a thirty-second aspect of the present invention, in
the image processing apparatus as defined in the thirty-first
aspect of the invention, said intra-frame prediction means
comprises an intra-frame predictor for generating intra-frame
predicted values of quantized values corresponding to a decoding
target block from quantized values corresponding to an already
decoded block located in the vicinity of the decoding target block,
according to intra-frame prediction information; and a first adder
for adding the intra-frame predicted values to the output of the
selected inverse scanner; and said inter-frame prediction means
comprises an inverse quantization unit for inverse-quantizing the
output of the first adder to output frequency components of a
difference signal corresponding to each block; an inverse frequency
transformation unit for performing inverse frequency transformation
to the frequency components to output a difference signal
corresponding to each block; a second adder for adding inter-frame
predicted values of an image signal corresponding to each block to
the difference signal to output an image signal corresponding to
each block; a frame memory for storing the output of the second
adder, as an image signal of an already decoded block as a
constituent of an already decoded display screen; and an
inter-frame predictor for generating the inter-frame predicted
values on the basis of inter-frame prediction information and an
image signal of an already coded block.
Thus, in decoding, switching is performed, on the basis of flag
information indicating switching of rearrangement, which
information is input together with an input signal of a decoding
target block to be subjected to decoding that is obtained by coding
various frequency components which have been subjected to an
inter-frame prediction process and an intra-frame prediction
process in a prescribed order, between the first rearrangement
operation in which the input signal is adaptively rearranged in an
order according to the kinds of both the prediction processes, and
the second rearrangement operation in which the input signal is
rearranged in a specific order, regardless of the kinds of both the
prediction processes. Therefore, accurate and efficient decoding
can be carried out to a bit stream which has been coded by
selecting one of plural scans for each of intra-coded macroblocks
and inter-coded macroblocks, according to a parameter concerning
prediction and a scan switching signal, thereby regenerating an
image signal.
According to a thirty-third aspect of the present invention, a data
recording medium contains an image processing program, which makes
a computer execute image processing in the image processing method
defined in any of the first to eighth, thirteenth to eighteenth,
twenty-fifth and twenty-seventh aspects. Therefore, the same effect
as in any of these aspects is obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus in accordance
with a first embodiment of the present invention.
FIGS. 2(a).about.2(d) are diagrams illustrating constructions of
scan control units which are used in the first and third
embodiments of the invention.
FIG. 3 is a flowchart showing a flow of an adaptive scan changing
method according to any of the first and second embodiments of the
invention.
FIG. 4 is a flowchart showing a flow of another adaptive scan
changing method according to any of the first and second
embodiments of the invention.
FIG. 5 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus according to a
modification of the first embodiment of the invention.
FIG. 6 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus in accordance
with a second embodiment of the present invention.
FIG. 7 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus according to a
modification of the second embodiment of the invention.
FIG. 8 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus in accordance
with a third embodiment of the present invention.
FIG. 9 is a flowchart showing a flow of an adaptive scan changing
method according to any of the third and fourth embodiments of the
invention.
FIG. 10 is a flowchart showing a flow of another adaptive scan
changing method according to any of the third and fourth
embodiments of the invention.
FIG. 11 is a block diagram illustrating a construction of an
image-coding apparatus as an image processing apparatus according
to a modification of the third embodiment of the invention.
FIG. 12 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus in accordance
with a fourth embodiment of the present invention.
FIG. 13 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus according to a
modification of the fourth embodiment of the invention.
FIG. 14 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus in accordance
with a fifth embodiment of the present invention.
FIG. 15 is a diagram illustrating a construction of a
characteristic analyzing unit which is used in any of the fifth and
sixth embodiments of the invention.
FIG. 16 is a flowchart showing a flow of an adaptive scan changing
method according to any of the fifth and sixth embodiments of the
invention.
FIG. 17 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus according to a
modification of the fifth embodiment of the invention.
FIG. 18 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus in accordance
with a sixth embodiment of the present invention.
FIG. 19 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus according to a
modification of the sixth embodiment of the invention.
FIG. 20 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus in accordance
with a seventh embodiment of the present invention.
FIG. 21 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus in accordance
with an eighth embodiment of the present invention.
FIG. 22 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus in accordance
with a ninth embodiment of the present invention.
FIG. 23 is a flowchart showing a flow of an adaptive scan changing
method according to any of the ninth and tenth embodiments of the
invention.
FIG. 24 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus in accordance
with a tenth embodiment of the present invention.
FIG. 25 is a diagram illustrating a construction of a data
recording medium in accordance with a thirteenth embodiment of the
present invention.
FIG. 26 is a block diagram illustrating a construction of an image
coding apparatus as a conventional image processing apparatus.
FIG. 27 is a diagram for explaining blocking of an image signal for
each unit of DCT processing.
FIG. 28 is a block diagram illustrating a construction of an image
decoding apparatus as a conventional image processing
apparatus.
FIG. 29 is a block diagram illustrating a construction of another
image coding apparatus as a conventional image processing
apparatus.
FIG. 30 is a diagram for conceptually explaining an intra-frame
prediction method.
FIGS. 31(a).about.31(c) are diagrams each illustrating the scanning
order in a scan which is selected in a scan changing method.
FIG. 32 is a block diagram illustrating a construction of another
image decoding apparatus as a conventional image processing
apparatus.
FIG. 33 is a block diagram illustrating a construction of still
another image coding apparatus as a conventional image processing
apparatus.
FIG. 34 is a block diagram illustrating a construction of still
another image decoding apparatus as a conventional image processing
apparatus.
FIG. 35 is a block diagram illustrating a construction of an image
coding apparatus as an image processing apparatus in accordance
with an eleventh embodiment of the present invention.
FIG. 36 is a flowchart showing a flow of a scan changing method
according to the eleventh embodiment of the invention.
FIG. 37 is a block diagram illustrating a construction of an image
decoding apparatus as an image processing apparatus in accordance
with a twelfth embodiment of the present invention.
FIG. 38 is a flowchart showing a flow of a scan changing method
according to the twelfth embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A description will be given of embodiments of the present invention
with reference to drawings.
[Embodiment 1]
FIG. 1 is a block diagram illustrating a construction of an image
processing apparatus according to a first embodiment of the present
invention. In FIG. 1, reference numeral 100a designates the image
processing apparatus (image coding apparatus) according to the
first embodiment of the invention. This image coding apparatus 100a
includes the construction, of the conventional image coding
apparatus 200a shown in FIG. 26, and a circuit construction for
performing adaptive scan changing processing in which a scan method
is changed according to a DCT (discrete cosine transformation) type
of a coding target block. Herein, the DCT type represents a signal
indicating whether the coding target block has been subjected to
frame DCT processing or field DCT processing.
That is, the image coding apparatus 100a according to the first
embodiment of the invention has a scanning unit 100a1 for
performing the above-mentioned adaptive scan changing processing,
in place of the scanner 109 in the conventional image coding
apparatus 200a, and the other construction of the image coding
apparatus 100a is the same as the image coding apparatus 200a.
This scanning unit 100a1 consists of n pieces of scanners
109s1.about.109sn having different scan methods, i.e., each setting
the different processing order to quantized values, a first switch
108a for selecting one of the scanners 109s1.about.109sn on the
basis of a control signal 116 and supplying an output 107 of the
quantization unit 106 to the selected scanner, a second switch 110a
for selecting one of the scanners 109s1.about.109sn on the basis of
the control signal 116 and supplying an output 111 of the selected
scanner to the variable-length coding unit (hereinafter referred to
as VLC unit) 112, and a scan control unit 115 for generating the
control signal 116 on the basis of DCT type information 114 which
is output from the blocking unit 102.
A description is given of the operation.
When an interlaced image signal 101 is input to the image coding
apparatus 100a, the blocking unit 102 blocks the interlaced image
signal 101 frame by frame or field by field, and outputs an image
signal (plural pixel values) 103 corresponding to each block.
Further, the blocking unit 102 outputs a DCT type signal 114
indicating a blocking unit of the image signal 103. The DCT unit
104 transforms the image signal 103 into DCT coefficients 105 by
DCT, and outputs the DCT coefficients 105 corresponding to each
block. The quantization unit 106 converts the DCT coefficients 105
into quantized values 107 by quantization.
At this time, the scan control unit 115 outputs a control signal
116 for controlling the switches 108a and 110a, according to the
DCT type signal 114. In the scanning unit 100a1, one of the
scanners 109s1.about.109sn is selected on the basis of the control
signal 116, and the quantized values 107 are scanned by the
selected scanner. Thereby, the processing order for coding is set
to the quantized values 107. Then, the quantized values 111 to
which the processing order has been set are output to the VLC unit
112. The VLC unit 112 performs variable-length coding to the
quantized values 111 according to the set order, and outputs the
coded quantized values as a bit stream 113.
FIG. 2(a) shows a circuit construction of the scan control unit 115
in the image coding apparatus 100a.
In this case, the scan control unit 115 consists of a decision unit
501, which receives the DCT type signal 114 and outputs the control
signal 116 to the switches 108a and 110a so that the switches
select a scanner which is to perform a scan suitable for the DCT
type of the coding target block.
A processing method by the decision unit 501 is described using a
flowchart shown in FIG. 3.
In step 601, the decision unit 501 decides the DCT type of the
coding target block on the basis of the DCT type signal 114. As the
result of the decision, when the coding target block is a frame DCT
block, the decision unit 501 outputs the control signal 116 for
selecting the scanner 109s1 (1) (step 602). Meanwhile, when the
coding target block is a field DCT block, the decision unit 501
outputs the control signal 116 for selecting the scanner 109s2 (2)
(step 603).
The scanner (1) performs a scan for setting the processing order
for coding quantized values, which scan is suitable for a frame DCT
block. For example, a scan in the order shown in FIG. 31(a) is
executed. The scanner (2) performs a scan which is suitable for a
field DCT block. For example, a scan in the order shown in FIG.
31(c) is executed.
In the above-mentioned construction, a suitable scan is selected
according to a DCT type of a coding target block. Therefore, in
interlaced image coding in which frame DCT blocks and field DCT
blocks coexist, a run length is increased, thereby improving coding
efficiency.
In addition, although in the first embodiment of the invention, the
construction of the scan control unit in FIG. 2(a) is described, a
circuit construction shown in FIG. 2(b) may be employed.
A scan control unit 115a shown in FIG. 2(b) consists of a decision
unit 502 and a memory 503 for storing DCT type signals of already
coded blocks.
In this scan control unit 115a, the decision unit 502 selects a
scan suitable for the coding target block on the basis of the DCT
type signal 114 of the coding target block and a DCT type signal
504 of an already coded block, and outputs the control signal 116
to the switches 108a and 110a so that the selected scan is
performed to the quantized values of the coding target block.
A processing method by the decision unit 502 is described using a
flowchart shown in FIG. 4.
In step 701, the decision unit 502 decides the DCT type of the
coding target block on the basis of the DCT type signal 114. As the
result of the decision, when the coding target block is a frame DCT
block, the decision unit 502 decides a DCT type of an adjacent
block which has been already coded, on the basis of the DCT type
signal 504 of the already coded block (step 702). Meanwhile, when
the coding target block is a field DCT block, the decision unit 502
decides a DCT type of an adjacent block which has been already
coded, on the basis of the DCT type signal 504 of the already coded
block (step 703).
As the result of the decision at step 702, when the already coded
block is a frame DCT block, the decision unit 502 outputs the
control signal 116 for selecting the scanner 109s1 (1) (step 704).
On the other hand, when the already coded block is a field DCT
block, the decision unit 502 outputs the control signal 116 for
selecting the scanner 109s2 (2) (step 705).
As the result of the decision at step 703, when the already coded
block is a frame DCT block, the decision unit 502 outputs the
control signal 116 for selecting the scanner 109s3 (3) (step 706).
On the other hand, when the already coded block is a field DCT
block, the decision unit 502 outputs the control signal 116 for
selecting the scanner 109s4 (4) (step 707).
In this way, by combining the DCT types of the coding target block
and the adjacent block, four scans are respectively selected at
steps 704, 705, 706 and 707.
More specifically, when both the coding target block and the
adjacent block have been subjected to field DCT processing, it is
thought that the image signal of the coding target block includes
more high-frequency components. Therefore, a scan which gives a
priority to quantized values corresponding to its high-frequency
components is selected at step 704. When either the coding target
block or the adjacent block has been subjected to field DCT
processing, it is thought that the image signal of the coding
target block includes slightly more high-frequency components.
Therefore, scans which slightly give a priority to quantized values
corresponding to its high-frequency components are selected at
steps 705 and 706.
When both the coding target block and the adjacent block have been
subjected to frame DCT processing, it is thought that the image
signal of the coding target block includes fewer high-frequency
components. Therefore, a scan which gives a priority to quantized
values corresponding to low-frequency components is selected at
step 707.
In the above-mentioned construction, both a DCT type of a coding
target block and a DCT type of an adjacent block are used for
decision. Accordingly, scanning processing is controlled more
finely and a more suitable scan is selected, as compared with the
case of the method shown in FIG. 3 (refer to FIG. 2(a)).
Consequently, a run length is more increased, resulting in further
improved coding efficiency.
In addition, although in the first embodiment of the invention, the
adaptive scan operation is always performed in coding, the coding
may be switched between the operation of carrying out the adaptive
scan and the operation of carrying out no adaptive scan, according
to prescribed control signals.
FIG. 5 is a block diagram illustrating an image coding apparatus
according to a modification of the first embodiment of the
invention. In FIG. 5, reference numeral 100a' designates the image
coding apparatus according to the modification of the first
embodiment. This image coding apparatus 100a' has a scanning unit
100a1' which performs switching between a scan mode for performing
the adaptive scan operation and a scan mode for performing no
adaptive scan operation according to a scan mode switching signal
1201, in place of the scanning unit 100a1 which always performs the
adaptive scan operation, in the image coding apparatus 100a
according to the first embodiment.
The scanning unit 100a1' includes the scanning unit 100a1 according
to the first embodiment, and a mode switch 1203a which selects one
of the control signal 116 from the scan control unit 115 and a
preset scan selecting signal 1202 for selecting a specific one from
among plural scanners, according to the scan mode switching signal
1201, and outputs the selected signal as a control signal 1204 for
the switches 108a and 110a.
Herein, the scan mode switching signal 1201 is supplied, by manual
operation, from the outside of the system (image coding apparatus).
The scan selecting signal 1202 selects a specific scan suitable for
an interlaced image, for example, a scan in the order shown in FIG.
31(c). In addition, the scan mode switching signal 1201 may be
output according to the result which is obtained by monitoring the
coding efficiency on the basis of the output 113 of the VLC unit
112.
In the construction according to the modification of the first
embodiment, an adaptive scan is switched to OFF to execute a
specific scan when required, whereby coding can be efficiently
simplified.
In any of the first embodiment and its modification, a description
is given of the image coding apparatus which performs switching
between frame DCT processing and field DCT processing in coding of
an interlaced image signal. However, the image coding apparatus may
have a construction for performing, in coding a progressive image,
switching between frame DCT and field DCT according to the content
of the image.
In this case, in coding of a specific progressive image, in which
switching between frame DCT and field DCT is performed according to
the content of the image, the efficiency of variable-length coding
can be improved.
[Embodiment 2]
FIG. 6 is a block diagram illustrating a construction of an image
processing apparatus according to a second embodiment of the
present invention. In FIG. 6, reference numeral 100b designates the
image processing apparatus (image decoding apparatus) according to
the second embodiment of the invention. This image decoding
apparatus 100b includes the construction of the conventional image
decoding apparatus 200b shown in FIG. 28, and a circuit
construction for performing adaptive inverse scan changing
processing in which an inverse scan method is changed according to
a DCT type of a decoding target block. Herein, the DCT type
represents a signal indicating whether a coded block corresponding
to the decoding target block has been subjected to frame DCT
processing or field DCT processing.
That is, the image decoding apparatus 100b according to the second
embodiment of the invention has an inverse scanning unit 100b1 for
performing the above-mentioned adaptive inverse scan changing
processing, in place of the inverse scanner 202 in the conventional
image decoding apparatus 200b, and the other construction of the
image decoding apparatus 100b is the same as the image decoding
apparatus 200b.
This inverse scanning unit 100b1 consists of n pieces of inverse
scanners 202s1.about.202sn having different inverse scan methods,
i.e., each performing different rearrangement for returning
quantized values which have been rearranged to the original order,
a first switch 108b for selecting one of the inverse scanners
202s1.about.202sn on the basis of a control signal 116 and
supplying an output 111 of the variable-length decoding unit
(hereinafter referred to as VLD unit) 201 to the selected inverse
scanner, a second switch 110b for selecting one of the inverse
scanners 202s1.about.202sn on the basis of the control signal 116
and supplying an output 107 of the selected inverse scanner to the
inverse quantization unit 203, and an inverse scan control unit
115b for generating the control signal 116 on the basis of the DCT
type information 114 which is output from the blocking unit 102 in
the image coding apparatus 100a.
A description is given of the operation.
When a bit stream 113 output from the image coding apparatus 100a
is input to the image decoding apparatus 110b, the VLD unit 201
performs variable-length decoding to the bit stream 113 to convert
the bit stream 113 into quantized values 111, and outputs the
quantized values 111. At this time, the inverse scan control unit
115b outputs a control signal 116 for selecting an inverse scanner
to the switches 108b and 110b, on the basis of a DCT type signal
114 from the image coding apparatus 100a.
The quantized values 111 are inverse-scanned by the inverse scanner
which is selected on the basis of the control signal 116, thereby
outputting quantized values 107 in the order before rearrangement
in coding. Then, the inverse quantization unit 203
inverse-quantizes the quantized values 107, and outputs DCT
coefficients 105 corresponding to a decoding target block. The
inverse DCT unit 204 transforms the DCT coefficients 105 into an
image signal (plural pixel values) 103 corresponding to the
decoding target block by inverse DCT. The inverse blocking unit 205
inverse-blocks the image signals 103 according to the DCT type
signal 114, thereby outputting an image signal 101 corresponding to
a single display screen.
In the image decoding apparatus 100b thus constructed, decoding
using an adaptive inverse scan changing method is performed.
Therefore, in variable-length decoding of DCT coefficients of a
progressive image or an interlaced image, accurate and efficient
decoding can be carried out to a bit stream which has been coded
using the adaptive scan changing method according to the first
embodiment, thereby regenerating an image signal.
In addition, in the second embodiment of the invention, an inverse
scanner is selected on the basis of a DCT type signal of a decoding
target block. As described in the first embodiment, however, an
inverse scanner may be selected on the basis of both a DCT type
signal of a decoding target block and a DCT type signal of an
already decoded block adjacent to the decoding target block.
Although in the second embodiment of the invention, the adaptive
inverse scan operation is always performed in decoding, the
decoding may be switched between the operation of carrying out the
adaptive inverse scan and the operation of carrying out no adaptive
inverse scan, according to prescribed control signals.
FIG. 7 is a block diagram illustrating an image decoding apparatus
according to a modification of the second embodiment of the
invention. In FIG. 7, reference numeral 100b' designates the image
decoding apparatus according to the modification of the second
embodiment. This image decoding apparatus 100b' has an inverse
scanning unit 100b1' which performs switching between a scan mode
for performing the adaptive inverse scan operation and a scan mode
for performing no adaptive inverse scan operation according to a
scan mode switching signal 1201, in place of the inverse scanning
unit 100b1 which always performs the adaptive inverse scan
operation in decoding, in the image decoding apparatus 100b
according to the second embodiment.
The inverse scanning unit 100b1' includes the inverse scanning unit
100b1 according to the second embodiment, and a mode switch 1203b
which selects one of the control signal 116 from the inverse scan
control unit 115b and a preset inverse scan selecting signal 1202b
for selecting a specific one from among plural inverse scanners,
according to the scan mode switching signal 1201, and outputs the
selected signal as a control signal 1204 for the switches 108b and
110b.
Herein, like the scan selecting signal 1202 in the image coding
apparatus 100a', the inverse scan selecting signal 1202b selects a
specific inverse scan suitable for an inter-laced image, for
example, an inverse scan corresponding to a scan shown in FIG.
31(c).
In the construction according to the modification of the second
embodiment, in decoding, an adaptive inverse scan is switched to
OFF to execute a specific inverse scan when required. Therefore,
when an adaptive scan is switched to OFF to execute a specific scan
in the image coding apparatus, a coded image signal can be
accurately decoded.
In any of the second embodiment and its modification, a description
is given of the image decoding apparatus corresponding to the image
coding apparatus which performs switching between frame DCT
processing and field DCT processing in coding of an interlaced
image signal. However, the image decoding apparatus may have a
construction corresponding to an image coding apparatus which
performs, in coding a-progressive image, switching between frame
DCT and field DCT according to the content of the image.
In this case, a coded image signal obtained by coding of a specific
progressive image, in which switching between frame DCT and field
DCT is performed according to the content of the image, can be
accurately decoded.
[Embodiment 3]
FIG. 8 is a block diagram illustrating a construction of an image
processing apparatus according to a third embodiment of the present
invention. In FIG. 8, reference numeral 100c designates the image
processing apparatus (image coding apparatus) according to the
third embodiment of the invention. This image coding apparatus 100c
has a scan control unit 310c for generating a control signal 116 on
the basis of both first prediction information (a first parameter
concerning intra-frame prediction) 309a and DCT type information
114 of a coding target block, in place of the scan control unit
1401c in the conventional image coding apparatus 200c shown in FIG.
29.
Herein, as in the conventional image coding apparatus 200c, the
first parameter 309a concerning intra-frame prediction includes
ON/OFF information and prediction direction information of AC
prediction, and second prediction information (a second parameter)
309b includes only ON/OFF information of AC prediction.
As mentioned above, unlike the first prediction information 309a
used for scan control in the image coding apparatus, the second
prediction information 309b transmitted to the decoding side
includes no prediction direction information. Accordingly, even
when a prediction method is changed, it is not required to change
the content of the second prediction information 309b to be output
to the decoding side, thereby easily dealing with the changed
prediction method. However, the second prediction information 309b
may include not only the ON/OFF information of AC prediction but
the prediction direction information, like the first prediction
information 309a.
That is, the image coding apparatus 100c according to the third
embodiment of the invention is different from the image coding
apparatus according to the first embodiment, in that a prediction
unit 100c2 for performing intra-frame prediction is added, and that
the first parameter 309a concerning intra-frame prediction is used
for scan control and the second parameter 309b is output to the
decoding side.
In addition, in the image coding apparatus 100c, switches 108c and
110c and n pieces of scanners 109s1.about.109sn of a scanning unit
100c1 have the same constructions as those of the scanning unit
100a1 according to the first embodiment, which are shown in FIG.
1.
A description is given of the operation. The same operation as in
the image coding apparatus 100a according to the first embodiment
is not described.
The predictor 305 generates predicted values of quantized values
107 of a coding target block from quantized values 306 of an
already coded block, and outputs these predicted values 303.
Further, the predictor 305 outputs first and second parameters 309a
and 309b concerning generation of the predicted values 303. Then,
the adder 301 performs subtraction of the predicted values 303 from
the quantized values 107, and outputs resulting difference values
302. The scan control unit 310c outputs a control signal 116 to the
switches 108c and 110c, according to a DCT type signal 114 and the
first parameter 309a. One of the scanners 109s1.about.109sn is
selected on the basis of the control signal 116, and the difference
values 302 are scanned by the selected scanner, thereby outputting
difference values 307. The VLC unit 112 performs variable-length
coding to the difference values 307, and outputs a resulting bit
stream 308. In addition, the adder 304 performs adding of the
predicted values 303 to the difference values 302, and outputs the
result of the addition as quantized values 306 of an already coded
block.
FIG. 2(c) shows a circuit construction of the scan control unit
310c.
In FIG. 2(c), the scan control unit 310c consists of a decision
unit 505, which receives the DCT type signal 114 and the first
parameter 309a concerning intra-frame prediction and outputs the
control signal 116 to the switches 108c and 110c so that the
switches select a scanner suitable for the DCT type of the coding
target block and a scan by the selected scanner is performed to the
quantized DCT coefficients.
A processing method by the decision unit 505 is described using a
flowchart shown in FIG. 9.
In step 801, the decision unit 505 decides the DCT type of the
coding target block on the basis of the DCT type signal 114. As the
result of the decision, when the coding target block is a field DCT
block, the decision unit 505 outputs the control signal 116 for
selecting the scanner (4) (step 807).
Meanwhile, when the coding target block is a frame DCT block,
ON/OFF decision of AC prediction is executed in step 802. As the
result of the decision at step 802, when the AC prediction is in
the OFF state, the decision unit 505 outputs the control signal 116
for selecting the scanner (3) (step 806).
When the AC prediction is in the ON state, decision of a reference
direction for prediction is executed in step 803. As the result of
the decision at step 803, when the reference direction is
horizontal, the decision unit 505 outputs the control signal 116
for selecting the scanner (2) (step 805). When the reference
direction is vertical, the decision unit 505 outputs the control
signal 116 for selecting the scanner (1) (step 804).
The scanner (1) performs a scan suitable for a frame DCT block when
vertical prediction is performed. For example, a scan in the order
shown in FIG. 31(b) applies to the scan by the scanner (1). The
scanner (2) performs a scan suitable for a frame DCT block when
horizontal prediction is performed. For example, a scan in the
order shown in FIG. 31(c) applies to the scan by the scanner (2).
The scanner (3) performs a scan suitable for a frame DCT block when
AC prediction is not performed. For example, a scan in the order
shown in FIG. 31(a) applies to the scan by the scanner (3). The
scanner (4) performs a scan suitable for a field DCT block. For
example, a scan in the order shown in FIG. 31(c) applies to the
scan by the scanner (4).
In the above-mentioned construction according to the third
embodiment of the invention, a suitable scan is selected according
to not only a first parameter concerning intra-frame prediction,
i.e., ON/OFF information and reference direction information of AC
prediction, but a DCT type of a coding target block. Therefore, in
interlaced image coding in which frame DCT blocks and field DCT
blocks coexist, a run length is increased, thereby improving coding
efficiency.
In addition, although in the third embodiment of the invention, the
construction of the scan control unit in FIG. 2(c) is described, a
circuit construction shown in FIG. 2(d) may be employed.
A scan control unit 310a shown in FIG. 2(d) consists of a decision
unit 506 and a memory 503 for storing DCT type signals of already
coded blocks.
In this scan control unit 310a, a DCT type signal 504 of an already
coded block is stored in the memory 503. The decision unit 506
selects a scanner suitable for the coding target block on the basis
of the DCT type signal 114 of the coding target block, the DCT type
signal 504 of the already coded block, and the first parameter 309a
concerning intra-frame prediction, and outputs the control signal
116 to the switches 108c and 110c so that a scan by the selected
scanner is performed to the output of the prediction unit.
A processing method by the decision unit 506 is described using a
flowchart shown in FIG. 10. This processing method comprises a
combination of the methods shown in FIGS. 4 and 9.
In step 901, the decision unit 506 decides the DCT type of the
coding target block on the basis of the DCT type signal 114. As the
result of the decision, when the coding target block is a field DCT
block, the decision unit 506 decides a DCT type of an adjacent
block which has been already coded, on the basis of the DCT type
signal 504 of the adjacent block (step 903). As the result of the
decision at step 903, when the adjacent block is a field DCT block,
the decision unit 506 outputs the control signal 116 for selecting
the scanner (6) (step 911).
On the other hand, when the adjacent block is a frame DCT block,
the decision unit 506 outputs the control signal 116 for selecting
the scanner (5) (step 910).
As the result of the decision at step 901, when the coding target
block is a frame DCT block, the decision unit 506 decides a DCT
type of an adjacent block which has been already coded, on the
basis of the DCT type signal 504 of the adjacent block (step
902).
As the result of the decision at step 902, when the already coded
block is a field DCT block, the decision unit 506 outputs the
control signal 116 for selecting the scanner (4) (step 909).
Meanwhile, when the already coded block is a frame DCT block,
ON/OFF decision of AC prediction is executed in step 904. As the
result of the decision at step 904, when the AC prediction is in
the OFF state, the decision unit 506 outputs the control signal 116
for selecting the scanner (3) (step 908).
When the AC prediction is in the ON state, decision of a reference
direction for prediction is executed in step 905. As the result of
the decision at step 905, when the reference direction is
horizontal, the decision unit 506 outputs the control signal 116
for selecting the scanner (2) (step 907). When the reference
direction is vertical, the decision unit 506 outputs the control
signal 116 for selecting the scanner (1) (step 906).
In the above-mentioned construction, a suitable scan is selected
according to not only a first parameter concerning intra-frame
prediction and a DCT type of a coding target block but a DCT type
of an adjacent block. Accordingly, scanning processing is
controlled more finely and a more suitable scan is selected, as
compared with the case of the scan control method by the scan
control unit shown in FIG. 2(c). Consequently, a run length is more
increased, resulting in further improved coding efficiency.
In addition, although in the third embodiment of the invention, the
adaptive scan operation is always performed in coding, the coding
may be switched between the operation of carrying out the adaptive
scan and the operation of carrying out no adaptive scan, according
to prescribed control signals.
FIG. 11 is a block diagram illustrating an image coding apparatus
according to a modification of the third embodiment of the
invention. In FIG. 11, reference numeral 100c' designates the image
coding apparatus according to the modification of the third
embodiment. This image coding apparatus 100c' has a scanning unit
100c1' which performs switching between a scan mode for performing
the adaptive scan operation and a scan mode for performing no
adaptive scan operation according to a scan mode switching signal
1201, in place of the scanning unit 100c1 which always performs the
adaptive scan operation, in the image coding apparatus 100c
according to the third embodiment.
The scanning unit 100c1' includes the scanning unit 100c1 according
to the third embodiment, and a mode switch 1203 which selects one
of the control signal 116 from the scan control unit 310c and a
preset scan selecting signal 1202 for selecting a specific one from
among plural scanners, according to the scan mode switching signal
1201, and outputs the selected signal as a control signal 1204 for
the switches 108c and 110c.
Herein, the scan mode switching signal 1201 is supplied, by manual
operation, from the outside of the system (image coding apparatus).
The scan selecting signal 1202 selects a specific scan suitable for
an interlaced image, for example, a scan in the order shown in FIG.
31(c). In addition, the scan mode switching signal 1201 may be
output according to the result which is obtained by monitoring the
coding efficiency on the basis of the output 308 of the VLC unit
112.
In the construction according to the modification of the third
embodiment, an adaptive scan is switched to OFF to execute a
specific scan when required, whereby coding can be efficiently
simplified.
In any of the third embodiment and its modification, a description
is given of the image coding apparatus which performs switching
between frame DCT processing and field DCT processing in coding of
an interlaced image signal. However, the image coding apparatus may
have a construction for performing, in coding a progressive image,
switching between frame DCT and field DCT according to the content
of the image.
In this case, in coding of a specific progressive image, in which
switching between frame DCT and field DCT is performed according to
the content of the image, the efficiency of variable-length coding
can be improved,
[Embodiment 4]
FIG. 12 is a block diagram illustrating a construction of an image
processing apparatus according to a fourth embodiment of the
present invention. In FIG. 12, reference numeral 100d designates
the image processing apparatus (image decoding apparatus) according
to the fourth embodiment of the invention. This image decoding
apparatus 100d has an inverse scan control unit 310d for generating
a control signal 116 on the basis of both control prediction
information 309a' corresponding to first prediction information (a
first parameter concerning intra-frame prediction) 309a and DCT
type information 114 of a decoding target block, in place of the
inverse scan control unit 1401d in the conventional image decoding
apparatus 200d shown in FIG. 32.
That is, the image decoding apparatus 100d according to the fourth
embodiment of the invention is different from the image decoding
apparatus 100b according to the second embodiment, in that a
prediction unit 100d2 for performing intra-frame prediction is
added, and that the control prediction information 309a'
corresponding to the first parameter 309a concerning intra-frame
prediction is used for inverse scan control.
In addition, in the image decoding apparatus 10d, switches 108d and
110d and n pieces of inverse scanners 202s1.about.202sn of an
inverse scanning unit 100d1 have the same constructions as those
according to the second embodiment, which are shown in FIG. 6.
A description is given of the operation.
When a bit stream 308 output from the image coding apparatus 100c
is input to the image decoding apparatus 100d, the VLD unit 201
performs variable-length decoding to the bit stream 308 to convert
the bit stream 308 into difference values 307, and outputs the
difference values 307. At this time, the inverse scan control unit
310d outputs a control signal 116 for selecting an inverse scanner
to the switches 108d and 110d, on the basis of a DCT type signal
114 from the image coding apparatus 100c and control prediction
information 309a' from the prediction unit 100d2.
The difference values 307 are inverse-scanned by the inverse
scanner which is selected on the basis of the control signal 116,
thereby outputting difference values 302 in the order before
rearrangement in coding. Then, the prediction unit 100d2 converts
the difference values 302 into corresponding quantized values 107.
The inverse quantization unit 203 inverse-quantizes the quantized
values 107, and outputs DCT coefficients 105. The inverse DCT unit
204 transforms the DCT coefficients 105 into an image signal
(plural pixel values) 103 by inverse DCT. The inverse blocking unit
205 inverse-blocks the image signals 103 according to the DCT type
signal 114, thereby outputting an interlaced image signal 101
corresponding to a single display screen.
In the image decoding apparatus 100d thus constructed, decoding is
performed using an adaptive inverse scan changing method according
to not only control prediction information which is generated on
the basis of second prediction information from the image coding
apparatus 100c but DCT type information of a decoding target block.
Therefore, in variable-length decoding of DCT coefficients of a
progressive image or an interlaced image, accurate and efficient
decoding can be carried out to a bit stream which has been coded
using the adaptive scan changing method according to the third
embodiment, thereby regenerating an image signal.
In addition, in the fourth embodiment of the invention, an inverse
scanner is selected on the basis of a DCT type signal of a decoding
target block. As described in the third embodiment, however, an
inverse scanner may be selected on the basis of both a DCT type
signal of a decoding target block and a DCT type signal of an
already decoded block adjacent to the decoding target block.
Although in the fourth embodiment of the invention, the adaptive
inverse scan operation is always performed in decoding, the
decoding may be switched between the operation of carrying out the
adaptive inverse scan and the operation of carrying out no adaptive
inverse scan, according to prescribed control signals.
FIG. 13 is a block diagram illustrating an image decoding apparatus
according to a modification of the fourth embodiment of the
invention. In FIG. 13, reference numeral 100d' designates the image
decoding apparatus according to the modification of the fourth
embodiment. This image decoding apparatus 100d' has an inverse
scanning unit 100d1' which performs switching between a scan mode
for performing the adaptive inverse scan operation and a scan mode
for performing no adaptive inverse scan operation according to a
scan mode switching signal 1201, in place of the inverse scanning
unit 100d1 which always performs the adaptive inverse scan
operation in decoding, in the image decoding apparatus 100d
according to the fourth embodiment.
The inverse scanning unit 100d1' includes the inverse scanning unit
100d1 according to the fourth embodiment, and a mode switch 1203d
which selects one of the control signal 116 from the inverse scan
control unit 310d and a preset inverse scan selecting signal 1202d
for selecting a specific one from among plural inverse scanners,
according to the scan mode switching signal 1201, and outputs the
selected signal as a control signal 1204 for the switches 108d and
110d.
Herein, like the scan selecting signal 1202 in the image coding
apparatus 100c', the inverse scan selecting signal 1202d selects a
specific inverse scan suitable for an interlaced image, for
example, an inverse scan corresponding to a scan shown in FIG.
31(c).
In the construction according to the modification of the fourth
embodiment, in decoding, an adaptive inverse scan is switched to
OFF to execute a specific inverse scan when required. Therefore,
when an adaptive scan is switched to OFF to execute a specific scan
in the image coding apparatus, a coded image signal can be
accurately decoded.
In any of the fourth embodiment and its modification, a description
is given of the image decoding apparatus corresponding to the image
coding apparatus which performs switching between frame DCT
processing and field DCT processing in coding of an interlaced
image signal. However, the image decoding apparatus may have a
construction corresponding to an image coding apparatus which
performs, in coding a progressive image, switching between frame
DCT and field DCT according to the content of the image.
In this case, a coded image signal obtained by coding of a specific
progressive image, in which switching-between frame DCT and field
DCT is performed according to the content of the image, can be
accurately decoded.
[Embodiment 5]
FIG. 14 is a block diagram illustrating a construction of an image
processing apparatus according to a fifth embodiment of the present
invention. In FIG. 14, reference numeral 100e designates the image
processing apparatus (image coding apparatus) according to the
fifth embodiment of the invention. This image coding apparatus 100e
includes the construction of the conventional image coding
apparatus 200a shown in FIG. 26, and a circuit construction for
performing adaptive scan changing processing in which a scan method
for a coding target block is changed according to the optimum scan
method for at least one already coded block which is positioned in
the vicinity of the coding target block.
That is, the image coding apparatus 100e according to the fifth
embodiment of the invention has a scanning unit 100e1 for
performing the above-mentioned adaptive scan changing processing,
in place of the scanner 109 in the conventional image coding
apparatus 200a, and the other construction of the image coding
apparatus 100e is the same as the image coding apparatus 200a.
This scanning unit 100e1 consists of n pieces of scanners
109s1.about.109sn having different scan methods, i.e., each setting
the different processing order to quantized values, a first switch
108e for selecting one of the scanners 109s1.about.109sn on the
basis of a control signal 1306 and supplying an output 107 of the
quantization unit 106 to the selected scanner, and a second switch
110e for selecting one of the scanners 109s1.about.109sn on the
basis of the control signal 1306 and supplying an output 111 of the
selected scanner to the variable-length coding unit (hereinafter
referred to as VLC unit) 112.
The scanning unit 100e1 further consists of a characteristic
analyzing unit 1301 for deciding the optimum scan (the processing
order for coding) for the output 107 of the quantization unit 106,
a memory 1303 for storing the decision result as information 1302
indicating the optimum scan, and a scan control unit 1305 for
controlling the switches 108e and 110e according to the control
signal 1306 so that the optimum scan is performed to quantized
values of a coding target block on the basis of information stored
in the memory 1303, i.e., information 1304 about the optimum scans
for already coded blocks.
A description is given of the operation.
When an interlaced image signal 101 is input to the image coding
apparatus 100e, the blocking unit 102 blocks the interlaced image
signal 101 frame by frame or field by field, and outputs an image
signal (plural pixel values) 103 corresponding to each block.
Further, the blocking unit 102 outputs a DCT type signal 114
indicating a blocking unit of the image signal 103. The DCT unit
104 transforms the image signal 103 into DCT coefficients 105 by
DCT, and outputs the DCT coefficients 105 corresponding to each
block. The quantization unit 106 converts the DCT coefficients 105
into quantized values 107 by quantization.
At this time, the characteristic analyzing unit 1301 decides the
optimum scan for the quantized values 107 of the coding target
block, and outputs information 1302 indicating the optimum scan to
the memory 1303. The scan control unit 1305 outputs a control
signal 1306 for controlling the switches 108e and 110e, according
to information 1304 about the optimum scans of already coded blocks
which are stored in the memory 1303. Then, one of the scanners
109s1.about.109sn is selected on the basis of the control signal
1306, and the quantized values 107 are scanned by the selected
scanner. Thereby, the processing order for coding is set to the
quantized values 107. The quantized values 111 to which the
processing order has been set are output to the VLC unit 112. The
VLC unit 112 performs variable-length coding to the quantized
values 111 according to the set order, and outputs a resulting bit
stream 113.
FIG. 15 shows a detailed circuit construction of the characteristic
analyzing unit 1301 in the image coding apparatus 100e.
As shown in FIG. 15, the characteristic analyzing unit 1301
consists of n pieces of evaluation function circuits
1801f1.about.1801fn respectively having n pieces of evaluation
functions corresponding to the scanning orders of the scanners
109s1.about.109sn and outputting evaluation values
1802f1.about.1802fn when the quantized values 107 are scanned by
the respective scanners 109s1.about.109sn, and a decision unit 1803
which performs decision on the basis of the outputs of the
evaluation function circuits 1801f1.about.1801fn. Herein, the
decision unit 1803 compares the evaluation values
1802f1.about.1802fn with each other, decides the scan having the
highest evaluation as the optimum scan for the quantized values
107, and outputs the information 1302 indicating the optimum scan.
In other words, the decision unit 1803 decides a distribution of
the DCT coefficients (frequency transformation) corresponding to
each block which are obtained in the information source coding unit
200a1, on the basis of the evaluation values output from the
evaluation function circuits 1801f1.about.1801fn, and outputs the
information 1302 indicating the optimum scan on the basis of the
result of the decision.
In addition, in each of the above-mentioned evaluation functions,
the sum of plural (for example, 10) DCT coefficients which are
selected in the scanning order of the corresponding scanner is used
as the evaluation value. However, any function may be employed as
long as an evaluation value of the function is higher as a
corresponding scan produces higher variable-length coding
efficiency.
A processing method by the scan control unit 1305 is described
using a flowchart shown in FIG. 16.
In step 1601, the scan control unit 1305 decides whether the
optimum scans for an upper macroblock just above the coding target
block and for a left macroblock on the left side of the coding
target block are identical or not, on the basis of the information
1304 about the optimum scans of the already coded blocks which are
stored in the memory 1303. As the result of the decision, when the
optimum scan for the upper macroblock and that for the left
macroblock are different, the scan control unit 1305 outputs the
control signal 1306 for selecting the scanner 109s3 (3) (step
1605).
Meanwhile, when the optimum scan for the upper macroblock and that
for the left macroblock are identical, the scan control unit 1305
decides which of the scans (1).about.(n) the optimum scan for the
upper and left macroblocks is (step 1602). When the optimum scan
for the upper and left macroblocks is the scan (1), the scan
control unit 1305 outputs the control signal 1306 for selecting the
scanner 109s1 (1) (step 1603). When the optimum scan for the upper
and left macroblocks is the scan (2), the scan control unit 1305
outputs the control signal 1306 for selecting the scanner 109s2 (2)
(step 1604).
In the above-mentioned construction, a suitable scan is selected
according to the optimum scans for already coded blocks in the
vicinity of a coding target block. Therefore, in interlaced image
coding in which frame DCT blocks and field DCT blocks coexist, a
run length is increased, thereby improving coding efficiency.
In addition, although in the fifth embodiment of the invention, the
adaptive scan operation is always performed in coding, the coding
may be switched between the operation of carrying out the adaptive
scan and the operation of carrying out no adaptive scan, according
to prescribed control signals.
FIG. 17 is a block diagram illustrating an image coding apparatus
according to a modification of the fifth embodiment of the
invention. In FIG. 17, reference numeral 100e' designates the image
coding apparatus according to the modification of the fifth
embodiment. This image coding apparatus 100e' has a scanning unit
100e1' which performs switching between a scan mode for performing
the adaptive scan operation and a scan mode for performing no
adaptive scan operation according to a scan mode switching signal
1201, in place of the scanning unit 100e1 which always performs the
adaptive scan operation, in the image coding apparatus 100e
according to the fifth embodiment.
The scanning unit 100e1' includes the scanning unit 100e1 according
to the fifth embodiment, and a mode switch 1203e which selects one
of the control signal 116 from the scan control unit 1305 and a
preset scan selecting signal 1202 for selecting a specific one from
among plural scanners, according to the scan mode switching signal
1201, and outputs the selected signal as a control signal 1204 for
the switches 108e and 110e.
Herein, the scan mode switching signal 1201 is supplied, by manual
operation, from the outside of the system (image coding apparatus).
The scan selecting signal 1202 selects a specific scan suitable for
an interlaced image, for example, a scan in the order shown in FIG.
31(c). In addition, the scan mode switching signal 1201 may be
output according to the result which is obtained by monitoring the
coding efficiency on the basis of the output 113 of the VLC unit
112.
In the construction according to the modification of the fifth
embodiment, an adaptive scan is switched to OFF to execute a
specific scan when required, whereby coding can be efficiently
simplified.
In any of the fifth embodiment and its modification, a description
is given of the image coding apparatus which performs switching
between frame DCT processing and field DCT processing in coding of
an interlaced image signal. However, the image coding apparatus may
have a construction for performing, in coding a progressive image,
switching between frame DCT and field DCT according to the content
of the image.
In this case, in coding of a specific progressive image, in which
switching between frame DCT and field DCT is performed according to
the content of the image, the efficiency of variable-length coding
can be improved.
[Embodiment 6]
FIG. 18 is a block diagram illustrating a construction of an image
processing apparatus according to a sixth embodiment of the present
invention. In FIG. 18, reference numeral 100f designates the image
processing apparatus (image decoding apparatus) according to the
sixth embodiment of the invention. This image decoding apparatus
100f includes the construction of the conventional image decoding
apparatus 200b shown in FIG. 28, and a circuit construction for
performing adaptive inverse scan changing processing in which an
inverse scan method for a decoding target block is changed
according to the optimum inverse scan method for at least one
already decoded block which is positioned in the vicinity of the
decoding target block.
That is, the image decoding apparatus 100f according to the sixth
embodiment of the invention has an inverse scanning unit 100f1 for
performing the above-mentioned adaptive inverse scan changing
processing, in place of the inverse scanner 202 in the conventional
image decoding apparatus 200b, and the other construction of the
image decoding apparatus 100f is the same as the conventional image
decoding apparatus 200b.
This inverse scanning unit 100f1 consists of n pieces of inverse
scanners 202s1.about.202sn having different inverse scan methods,
i.e., each performing different rearrangement for returning
quantized values which have been rearranged to the original order,
a first switch 108f for selecting one of the inverse scanners
202s1.about.202sn on the basis of a control signal 1306 and
supplying an output 111 of the variable-length decoding unit
(hereinafter referred to as VLD unit) 201 to the selected inverse
scanner, and a second switch 110f for selecting one of the inverse
scanners 202s1.about.202sn on the basis of the control signal 1306
and supplying an output 107 of the selected inverse scanner to the
inverse quantization unit 203.
The inverse scanning unit 100f1 further consists of a
characteristic analyzing unit 1301 for deciding the optimum inverse
scan for the output 107 of the inverse scanner, a memory 1303 for
storing the decision result as information 1302 indicating the
optimum inverse scan, and an inverse scan control unit 1305f for
generating the control signal 1306 for selecting the optimum
inverse scan for a decoding target block, on the basis of
information about the optimum inverse scans for already decoded
blocks, which are stored in the memory 1303. Herein, the
characteristic analyzing unit 1301 has the same construction as in
the fifth embodiment.
A description is given of the operation.
When a bit stream 113 output from the image coding apparatus 100e
is input to the image decoding apparatus 100f, the VLD unit 201
converts the bit stream 113 into quantized values 111 by
variable-length decoding, and outputs the quantized values 111. At
this time, the inverse scan control unit 1305f outputs a control
signal 1306 for selecting one of the plural inverse scanners
202s1.about.202sn to the switches 108f and 110f, on the basis of
information 1304 about the optimum inverse scans of already decoded
blocks which are stored in the memory 1303.
The quantized values 111 are inverse-scanned by the inverse scanner
which is selected according to the control signal 1306, thereby
outputting quantized values 107 in the order before rearrangement
in coding. Then, the inverse quantization unit 203
inverse-quantizes the quantized values 107, and outputs DCT
coefficients 105 corresponding to a decoding target block. The
inverse DCT unit 204 transforms the DCT coefficients 105 into an
image signal (plural pixel values) 103 corresponding to the
decoding target block by inverse DCT. The inverse blocking unit 205
inverse-blocks the image signals 103 according to the DCT type
signal 114, thereby outputting an image signal 101 corresponding to
a single display screen. In addition, the characteristic analyzing
unit 1301 decides the optimum inverse scan for the quantized values
107 of the decoding target block, and outputs information 1302
indicating the optimum inverse scan to the memory 1303.
In the image decoding apparatus 100f thus constructed, decoding
using an adaptive inverse scan changing method is performed.
Therefore, in variable-length decoding of DCT coefficients of a
progressive image or an interlaced image, accurate and efficient
decoding can be carried out to a bit stream which has been coded
using the adaptive scan changing method according to the fifth
embodiment, thereby regenerating an image signal.
In addition, although in the sixth embodiment of the invention, the
adaptive inverse scan operation is always performed in decoding,
the decoding may be switched between the operation of carrying out
the adaptive inverse scan and the operation of carrying out no
adaptive inverse scan, according to prescribed control signals.
FIG. 19 is a block diagram illustrating an image decoding apparatus
according to a modification of the sixth embodiment of the
invention. In FIG. 19, reference numeral 100f' designates the image
decoding apparatus according to the modification of the sixth
embodiment. This image decoding apparatus 100f' has an inverse
scanning unit 100f1' which performs switching between a scan mode
for performing the adaptive inverse scan operation and a scan mode
for performing no adaptive inverse scan operation according to a
scan mode switching signal 1201, in place of the inverse scanning
unit 100f1 which always performs the adaptive inverse scan
operation in decoding, in the image decoding apparatus 100f
according to the sixth embodiment.
The inverse scanning unit 100f1' includes the inverse scanning unit
100f1 according to the sixth embodiment, and a mode switch 1203f
which selects one of the control signal 1306 from the inverse scan
control unit 1305f and a preset inverse scan selecting signal 1202e
for selecting a specific one from among plural inverse scanners,
according to the scan mode switching signal 1201, and outputs the
selected signal as a control signal 1204 for the switches 108f and
110f.
In the construction according to the modification of the sixth
embodiment, in decoding, an adaptive inverse scan is switched to
OFF to execute a specific inverse scan when required. Therefore,
when an adaptive scan is switched to OFF to execute a specific scan
in the image coding apparatus, a coded image signal can be
accurately decoded.
In any of the sixth embodiment and its modification, a description
is given of the image decoding apparatus corresponding to the image
coding apparatus which performs switching between frame DCT
processing and field DCT processing in coding of an interlaced
image signal. However, the image decoding apparatus may have a
construction corresponding to an image coding apparatus which
performs, in coding a progressive image, switching between frame
DCT and field DCT according to the content of the image.
In this case, a coded image signal obtained by coding of a specific
progressive image, in which switching between frame DCT and field
DCT is performed according to the content of the image, can be
accurately decoded.
[Embodiment 7]
FIG. 20 is a block diagram illustrating a construction of an image
processing apparatus according to a seventh embodiment of the
present invention. In FIG. 20, reference numeral 100g designates
the image processing apparatus (image coding apparatus) according
to the seventh embodiment of the invention. This image coding
apparatus 100g has a scanning unit 100g1 which performs switching
between a scan mode for performing the adaptive scan operation and
a scan mode for performing no adaptive scan operation, when
required, in place of the scanning unit 200c1 which always performs
the adaptive scan operation in coding, in the conventional image
coding apparatus 200c shown in FIG. 29.
This scanning unit 100g1 includes the scanning unit 200c1 in the
conventional image coding apparatus 200c, and a mode switch 1203g
which selects one of a control signal 116 from the scan control
unit 1401c and a preset scan selecting signal 1202 for selecting a
specific one from among plural scanners, according to a scan mode
switching signal 1201, and outputs the selected signal as a control
signal 1204g for the switches 108c and 110c. The other construction
of the image coding apparatus 100g is the same as the conventional
image coding apparatus 200c.
In the image coding apparatus 100g thus constructed, the mode
switch 1203g selects one of the control signal 116 for adaptively
selecting one of plural scans and the scan selecting signal 1202
for selecting a specific scan suitable for an interlaced image,
according to the scan mode switching signal 1201 which is supplied,
by manual operation, from the outside of the system (image coding
apparatus), and supplies the selected signal to the switches 108c
and 110c.
At this time, when the mode switch 1203g selects the scan selecting
signal 1202, the switches 108c and 110c select the scanner 109s3
which is to perform a scan shown in FIG. 31(c), on the basis of the
scan selecting signal 1202, and the quantized values 107 are
scanned by the selected scanner 109s3, regardless of the first
prediction information 309a.
Meanwhile, when the mode switch 1203g selects the control signal
116, the scanning unit 100g1 performs scanning processing in the
same manner as the scanning unit 200c1 in the conventional image
coding apparatus 200c shown in FIG. 29.
The other operation is performed as in the conventional image
coding apparatus 200c.
In the construction according to the seventh embodiment of the
invention, an adaptive scan is switched to OFF to execute a
specific scan suitable for an interlaced image when required,
whereby coding of an interlaced image signal can be efficiently
simplified.
In addition, although the scan mode switching signal 1201 is
supplied by manual operation, it may be output according to the
result which is obtained by monitoring the coding efficiency on the
basis of the output 308 of the VLC unit 112.
Although in the seventh embodiment of the invention, a description
is given of coding of an interlaced image signal, an image signal
to be subjected to coding is not limited thereto. For example, it
may be a progressive image of a lateral stripe pattern or the like,
the image having high pixel value correlations between odd scan
lines or even scan lines, like an interlaced image. Also in this
case, the same effects as in the seventh embodiment are
obtained.
[Embodiment 8]
FIG. 21 is a block diagram illustrating a construction of an image
processing apparatus according to an eighth embodiment of the
present invention. In FIG. 21, 22 reference numeral 100h designates
the image processing apparatus (image decoding apparatus) according
to the eighth embodiment of the invention. This image decoding
apparatus 100h has an inverse scanning unit 100h1 which performs
switching between an inverse scan mode for performing the adaptive
inverse scan operation and an inverse scan mode for performing no
adaptive inverse scan operation, when required, in place of the
inverse scanning unit 200d1 which always performs the adaptive
inverse scan operation in decoding, in the conventional image
decoding apparatus 200d shown in FIG. 32.
This inverse scanning unit 100h1 includes the inverse scanning unit
200d1 in the conventional image decoding apparatus 200d, and a mode
switch 1203h which selects one of a control signal 116 from the
inverse scan control unit 1401d and a preset inverse scan selecting
signal 1202 for selecting a specific one from among plural inverse
scanners, according to a scan mode switching signal 1201, and
outputs the selected signal as a control signal 1204h for the
switches 108d and 110d. The other construction of the image
decoding apparatus 100h is the same as the conventional image
decoding apparatus 200d.
In the image decoding apparatus 100h thus constructed, the mode
switch 1203h selects one of the control signal 116 for adaptively
selecting one of plural inverse scans and the inverse scan
selecting signal 1202 for selecting a specific inverse scan
suitable for an interlaced image, according to the scan mode
switching signal 1201 which is supplied, by manual operation, from
the outside of the system (image decoding apparatus), and supplies
the selected signal to the switches 108d and 110d.
At this time, when the mode switch 1203h selects the inverse scan
selecting signal 1202, the switches 108d and 110d select the
inverse scanner 202s3 which is to perform an inverse scan
corresponding to a scan shown in FIG. 31(c), on the basis of the
inverse scan selecting signal 1202, and the quantized values 307
are inverse-scanned by the selected inverse scanner 202s3,
regardless of the control prediction information 309a'.
Meanwhile, when the mode switch 1203h selects the control signal
116, the inverse scanning unit 100h1 performs inverse-scanning
processing in the same manner as the inverse scanning unit 200d1 in
the conventional image decoding apparatus 200d shown in FIG.
32.
The other operation is performed as in the conventional image
decoding apparatus 200d.
In the construction according to the eighth embodiment of the
invention, an adaptive inverse scan is switched to OFF to execute a
specific inverse scan suitable for an interlaced image when
required, whereby decoding of a coded interlaced image signal can
be efficiently simplified.
In addition, although in the eighth embodiment of the invention, a
description is given of decoding of an interlaced image, an image
to be subjected to decoding is not limited thereto. For example, it
may be a progressive image of a lateral stripe pattern or the like,
the image having high pixel value correlations between odd scan
lines or even scan lines, like an interlaced image. Also in this
case, the same effects as in the eighth embodiment are
obtained.
[Embodiment 9]
FIG. 22 is a block diagram illustrating a construction of an image
processing apparatus according to a ninth embodiment of the present
invention. In FIG. 22, reference numeral 100i designates the image
processing apparatus (image coding apparatus) according to the
ninth embodiment of the invention. This image coding apparatus 100i
has a scanning unit 100i1 which adaptively changes a scan method on
the basis of both prediction information (a parameter) 1015, and a
scan mode switching signal 1201 which is supplied, by manual
operation, from the outside of the system (image coding apparatus),
in place of the scanning unit 200e1 in the conventional image
coding apparatus 200e shown in FIG. 33.
This scanning unit 100i1 consists of n pieces of scanners
199s1.about.199sn having different scan methods, i.e., each setting
the different processing order to quantized values, a first switch
108a for selecting one of the scanners 199s1.about.199sn on the
basis of a control signal 116i and supplying an output 107 of the
quantization unit 106 to the selected scanner, a second switch 110a
for selecting one of the scanners 199s1.about.199sn on the basis of
the control signal 116i and supplying an output 1005 of the
selected scanner to the variable-length coding (VLC) unit 112, and
a scan control unit 1501i for generating the control signal 116i on
the basis of the parameter 1015 concerning prediction from the
prediction unit 200e2 and the scan mode switching signal 1201 from
the outside.
Herein, more specifically, the scanner 199s1 (1) is constituted by
the respective elements 301, 304 and 305 in the prediction unit
200c2 shown in FIG. 29, and the respective elements 108c, 110c,
109s1.about.109s3 and 1401c in the scanning unit 200c1 shown in
FIG. 29. That is, the scanner (1) performs intra-frame prediction
to a block to which no inter-frame prediction has been performed in
coding (hereinafter referred to as an intra-coded block) and
selects one of the scanners 109s1.about.109s3 constituting the
scanner (1) on the basis of prediction information concerning
generation of predicted values. In addition, one of the scanners
109s1.about.109s3 constituting the scanner (1) performs a scan of
quantized values in the order shown in FIG. 31(a).
The scanner 199s2 (2) performs a scan in the order shown in FIG.
31(a), the scanner 199s3 (3) performs a scan in the order shown in
FIG. 31(c), and the scanner 199s4 (4) performs a scan in the order
shown in FIG. 31(a) or FIG. 31(c).
The other construction of the image coding apparatus 100i is the
same as in the conventional image coding apparatus 200e shown in
FIG. 33.
A description is given of the operation. The same operation as in
the conventional image coding apparatus 200e shown in FIG. 33 is
not described.
A processing method by the scan control unit 1501i is described
using a flowchart shown in FIG. 23.
In step 1701, the scan control unit 1501i decides an inter-frame
prediction parameter 1015 indicating information about coding of a
coding target block. As the result of the decision, when the coding
target block is an intra-coded block, decision of the scan mode
switching signal 1201 is performed (step 1702). As the result of
the decision at step 1702, when the scan mode switching signal 1201
is in the OFF state, the scan control unit 1501i outputs the
control signal 116i for selecting the scanner (1) (step 1704). On
the other hand, when the scan mode switching signal 1201 is in the
ON state, the scan control unit 1501i outputs the control signal
116i for selecting the scanner (3) (step 1705).
Meanwhile, as the result of the decision at step 1701, when the
coding target block is an inter-coded block, decision of the scan
mode switching signal 1201 is performed (step 1703). As the result
of the decision at step 1703, when the scan mode switching signal
1201 is in the OFF state, the scan control unit 1501i outputs the
control signal 116i for selecting the scanner (2) (step 1706). On
the other hand, when the scan mode switching signal 1201 is in the
ON state, the scan control unit 1501i outputs the control signal
116i for selecting the scanner (4) (step 1707).
In the image coding apparatus 100i thus constructed, since for each
of intra-coded macroblocks and inter-coded macroblocks, one of
plural scans is selected according to a parameter concerning
prediction and a scan mode switching signal, a scan suitable for
each coding method is performed. Therefore, in inter coding of an
interlaced image signal in which inter-coded macroblocks and
intra-coded macroblocks having different frequency component
distributions coexist, a run length is increased, thereby improving
coding efficiency.
In the ninth embodiment of the invention, a description is given of
the image coding apparatus which performs switching between frame
DCT processing and field DCT processing in coding of an interlaced
image signal. However, the image coding apparatus may have a
construction for performing, in coding a progressive image,
switching between frame DCT and field DCT according to the content
of the image.
In this case, in coding of a specific progressive image, in which
switching between frame DCT and field DCT is performed according to
the content of the image, the efficiency of variable-length coding
can be improved.
[Embodiment 10]
FIG. 24 is a block diagram illustrating a construction of an image
processing apparatus according to a tenth embodiment of the present
invention. In FIG. 24, reference numeral 100j designates the image
processing apparatus (image decoding apparatus) according to the
tenth embodiment of the invention. This image decoding apparatus
100j has an inverse scanning unit 100j1 which adaptively changes an
inverse scan method on the basis of both a prediction parameter
1015 and a scan mode switching signal 1201, in place of the inverse
scanning unit 200f1 in the conventional image decoding apparatus
200f shown in FIG. 34.
This inverse scanning unit 100j1 consists of n pieces of inverse
scanners 292s1.about.292sn having different inverse scan methods,
i.e., each performing different rearrangement for returning
quantized values which have been rearranged to the original order,
a first switch 108b for selecting one of the inverse scanners
292s1.about.292sn on the basis of a control signal 116i and
supplying an output 1005 of the variable-length decoding unit 201
to the selected inverse scanner, a second switch 110b for selecting
one of the inverse scanners 292s1.about.292sn on the basis of the
control signal 116i and supplying an output 1004 of the selected
inverse scanner to the inverse quantization unit 203, and an
inverse scan control unit 1501j for generating the control signal
116i on the basis of the parameter 1015 concerning prediction from
the prediction unit 200e2 and the scan mode switching signal 1201
from the outside. Herein, the inverse scanners 292s1.about.292sn
correspond to the scanners 199s1.about.199sn in the image coding
apparatus 100i.
The other construction of the image decoding apparatus 100j is the
same as in the conventional image decoding apparatus 200f shown in
FIG. 34.
The image decoding apparatus 100j is different from the
conventional image decoding apparatus 200f in that the inverse scan
control unit 1501j outputs the control signal 116i on the basis of
the parameter 1015 concerning prediction and the scan mode
switching signal 1201, using the same method as the scan control
unit 1501i according to the ninth embodiment.
In the image decoding apparatus 100j thus constructed, decoding is
performed by adaptively changing a scan according to a parameter
concerning prediction and a scan mode switching signal. Therefore,
in variable-length decoding of DCT coefficients of a progressive
image or an interlaced image, accurate and efficient decoding can
be carried out to a bit stream which has been coded using the scan
changing method according to the ninth embodiment, thereby
regenerating an image signal corresponding to the bit stream.
In the tenth embodiment of the invention, a description is given of
the image decoding apparatus corresponding to the image coding
apparatus which performs switching between frame DCT processing and
field DCT processing in coding of an interlaced image signal.
However, the image decoding apparatus may have a construction
corresponding to an image coding apparatus which performs, in
coding a progressive image, switching between frame DCT and field
DCT according to the content of the image.
In this case, a coded image signal obtained by coding of a specific
progressive image, in which switching between frame DCT and field
DCT is performed according to the content of the image, can be
accurately decoded.
[Embodiment 11]
FIG. 35 is a block diagram illustrating a construction of an image
processing apparatus according to an eleventh embodiment of the
present invention. In FIG. 35, reference numeral 100k designates
the image processing apparatus (image coding apparatus) according
to the eleventh embodiment of the invention. This image coding
apparatus 100k consists of a blocking unit 102, an information
source coding unit 100k1, a prediction unit 100k2, a scanning unit
100k3, and a variable-length coding (VLC) unit 112. The blocking
unit 102 is for dividing an input image signal 101 correspondingly
to plural blocks constituting a single display screen to generate
an image signal (plural pixel values) 103 corresponding to each
block. The information source coding unit 100k1 is for performing
information source coding to inter-frame difference values 1002
between the image signal (pixel values) 103 and inter-frame
predicted values 1008 of the image signal 103. The prediction unit
100k2 is for performing intra-frame prediction to an output
(quantized values) 1004 of the information source coding unit 100k1
to generate intra-frame predicted values 303, and outputting
intra-frame difference values 302 between the quantized values 1004
and intra-frame predicted values 303 of the quantized values 1004
and outputting first prediction information 309a and second
prediction information 309b. Herein, the first prediction
information 309a includes ON/OFF information indicating ON/OFF of
AC prediction and prediction direction information indicating a
reference direction for AC prediction, and the second prediction
information 309b includes only the ON/OFF information of AC
prediction. The scanning unit 100k3 is for changing a scan method
for the intra-frame difference values 302, on the basis of a
parameter concerning generation of the predicted values
(inter-frame prediction information) 1015 from the information
source coding unit 100k1, a scan mode switching signal 1201 which
is supplied, by manual operation, from the outside of the system
(image coding apparatus). The variable-length coding (VLC) unit 112
is for performing variable-length coding to an output 1005 of the
scanning unit 100k3 according to the order which has been set in
the scanning unit 100k3, to generate a bit stream 1006
corresponding to the image signal of each block.
In the eleventh embodiment of the invention, the information source
coding unit 100k1 has the same construction as the information
source coding unit 200e2 in the conventional image coding apparatus
200e shown in FIG. 33, and the prediction unit 100k2 has the same
construction as the prediction unit 200c2 in the conventional image
coding apparatus 200c shown in FIG. 29.
The scanning unit 100k3 according to the eleventh embodiment of the
invention consists of n pieces of scanners 199k1.about.199kn having
different scan methods, i.e., each setting the different processing
order to quantized values, a first switch 108a for selecting one of
the scanners 199k1.about.199kn on the basis of a control signal
116k and supplying the output 302 of the prediction unit 100k2 to
the selected scanner, a second switch 110a for selecting one of the
scanners 199k1.about.199kn on the basis of the control signal 116k
and supplying the output 1005 of the selected scanner to the VLC
unit 112, and a scan control unit 1501k for generating the control
signal 116k on the basis of the parameter concerning the prediction
(inter-frame prediction information) 1015 from the predictor 1012
in the information source coding unit 100k1, and the scan mode
switching signal 1201 from the outside.
That is, the scanning unit 100k3 is constructed so as to perform
switching between the first scan operation and the second scan
operation according to the scan mode switching signal 1201. In the
first scan operation, an intra-coded block is subjected to adaptive
scanning by the scanner 199k1, and an inter-coded block is
subjected to zigzag scanning by the scanner 199k2. In the second
scan operation, an intra-coded block is subjected to scanning which
gives a priority to a vertical direction, by the scanner 199k3, and
an inter-coded block is subjected to scanning which gives a
priority to a vertical direction in the order different from the
order of the scan by the scanner 199k3, by the scanner 199k4.
Herein, more specifically, the scanner 199k1 (1) is constituted by
the respective elements 108c, 110c, 109s1.about.109s3 and 1401c in
the scanning unit 200c1 shown in FIG. 29. That is, the scanner (1)
selects one of the scanners 109s1.about.109s3 constituting the
scanner (1) on the basis of first intra-frame prediction
information 309a concerning generation of predicted values for an
intra-coded block. In addition, one of the scanners
109s1.about.109s3 constituting the scanner (1) performs a zigzag
scan of quantized values in the order shown in FIG. 31(a).
The scanner 199k2 (2) performs a zigzag scan in the order shown in
FIG. 31(a). The scanner 199k3 (3) performs a scan which gives a
priority to a vertical direction in the order shown in FIG. 31(c).
The scanner 199k4 (4) performs a scan which gives a priority to a
vertical direction in the order different from the order shown in
FIG. 31(c).
The scan which gives a priority of a vertical direction is of
setting the processing order in which quantized values arranged
along a vertical direction corresponding to a vertical direction of
a display screen are continuous by a prescribed number, to
quantized values arranged in the form of a 8.times.8 matrix, which
are obtained by information source coding of an image signal
corresponding to each block.
A description is given of the operation.
When an interlaced image signal 101 is input to the image coding
apparatus 100k, the blocking unit 102 blocks the interlaced image
signal 101 frame by frame or field by field, and outputs an image
signal (plural pixel values) 103 corresponding to each block to the
information source coding unit 100k1. Further, the blocking unit
102 outputs a DCT type signal 114 indicating a blocking unit of the
image signal 103.
In the information source coding unit 100k1, inter-frame predictive
coding is carried out to the image signal (pixel values) 103 which
is obtained by blocking. Specifically, the DCT unit 104 transforms
difference values 1002 between the image signal (pixel values) 103
and inter-frame predicted values 1008 of the image signal 103 into
DCT coefficients 1003 by DCT, and outputs the DCT coefficients
1003. The quantization unit 106 converts the DCT coefficients 1003
into quantized values 1004 by quantization, and outputs the
quantized values 1004 to the prediction unit 100k2.
At this time, in the information source coding unit lookl, the
inverse quantization unit 203 converts the quantized values 1004
into DCT coefficients 1007 corresponding to the DCT coefficients
1003. The inverse DCT unit 204 transforms the DCT coefficients 1007
into difference signals 1009 corresponding to the difference values
1002. The adder 1010 adds the inter-frame predicted values 1008 to
the difference signals 1009, and the result of the addition 1011 is
stored in the frame memory 1014, as a reference image signal. In
the predictor 1012, the above-mentioned inter-frame predicted
values 1008 are generated on the basis of a reference image signal
1013 of an already coded block which is stored in the frame memory
1014, and the image signal 103 which is obtained by blocking.
In the image coding apparatus 100k, when intra-coding processing is
performed to a coding target block, the predictor 1012 in the
information source coding unit 100k1 outputs values at "0" level as
the inter-frame predicted values 1008. When inter-coding processing
is performed thereto, the predictor 1012 outputs the inter-frame
predicted values 1008 at the level corresponding to each block.
Next, in the prediction unit 100k2, intra-frame prediction is
carried out to the quantized values 1004 as the output of the
information source coding unit 100k1. Specifically, the adder 301
subtracts inter-frame predicted values 303 of the quantized values
1004 from the quantized values 1004, and outputs resulting
difference values 302 to the scanning unit 100k3. At this time, in
the prediction unit 100k2, the adder 304 adds the intra-frame
predicted values 303 to the difference values 302, and outputs the
result of the addition 306 to the predictor 305. In the predictor
305, the above-mentioned intra-frame predicted values 303 are
generated on the basis of the result of addition 306 of an already
coded block, using the method which has been described in FIG. 30,
and first and second parameters (first intra-frame prediction
information and second intra-frame prediction information) 309a and
309b concerning generation of the predicted values, are output from
the predictor 305.
Then, in the scanning unit 100k3, the output 302 of the prediction
unit 100k2 is subjected to prescribed scanning on the basis of the
intra-frame prediction information 309a, inter-frame prediction
information 1015, and a scan mode switching signal 1201.
A processing method by the scan control unit 1501k in the scanning
unit 100k3 is described using a flowchart shown in FIG. 36.
In step 1801, the scan control unit 1501k decides whether the
coding target block is subjected to intra coding or inter coding,
on the basis of the inter-frame prediction information 1015
concerning generation of the predicted values in inter-frame
predictive coding of the coding target block. As the result of the
decision, when the coding target block is an intra-coded block,
decision of the scan mode switching signal 1201 is performed (step
1802). As the result of the decision at step 1802, when the scan
mode switching signal 1201 is in the OFF state, the scan control
unit 1501k outputs the control signal 116k for selecting the
scanner 199k1 (1) (step 1804). Thereby, the difference values 302
which are obtained by performing intra-frame prediction to the
quantized values 1004 corresponding to the intra-coded block, are
subjected to adaptive scanning on the basis of the first
intra-frame prediction information 309a, by the scanner (1).
On the other band, when the scan mode switching signal 1201 is in
the ON state, the scan control unit 1501k outputs the control
signal 116k for selecting the scanner 199k3 (3) (step 1805).
Thereby, the difference values 302 which are obtained by performing
intra-frame prediction to the quantized values 1004 corresponding
to the intra-coded block, are subjected to scanning which gives a
priority to a vertical direction, by the scanner (3).
As the result of the decision at step 1801, when the coding target
block is an inter-coded block, decision of the scan mode switching
signal 1201 is performed (step 1803). As the result of the decision
at step 1803, when the scan mode switching signal 1201 is in the
OFF state, the scan control unit 1501k outputs the control signal
116k for selecting the scanner 199k2 (2) (step 1806). Thereby, the
difference values 302 which are obtained by performing intra-frame
prediction to the quantized values 1004 corresponding to the
inter-coded block, are subjected to zigzag scanning, by the scanner
(2).
On the other hand, when the scan mode switching signal 1201 is in
the ON state, the scan control unit 1501k outputs the control
signal 116k for selecting the scanner 199k4 (4) (step 1807).
Thereby, the difference values 302 which are obtained by performing
intra-frame prediction to the quantized values 1004 corresponding
to the inter-coded block, are subjected to scanning which gives a
priority to a vertical direction different from the vertical
direction of the scanner (3), by the scanner (4).
Then, the VLC unit 112 codes the quantized values of the coding
target block, according to the prescribed order which has been set
in the scanning unit 110k3, to output a bit stream (coded image
signal) 1006.
In the image coding apparatus 100k thus constructed, in coding of
an interlaced image signal, switching is performed between a first
coding mode and a second coding mode according to a scan mode
switching signal, wherein the first coding mode comprises
performing an adaptive scan to quantized values of an intra-coded
block, and performing a zigzag scan to quantized values of an
inter-coded block, and the second coding mode comprises performing
a scan which gives a priority to a first vertical direction to the
quantized values of the intra-coded block, and performing a scan
which gives a priority to a second vertical direction to the
quantized values of the inter-coded block. Therefore, in coding of
an interlaced image signal in which inter-coded blocks and
intra-coded blocks having different frequency component
distributions coexist, coding efficiency can be further
improved.
In addition, in the image coding apparatus 100k according to the
eleventh embodiment of the invention, the first intra-frame
prediction information 309a includes ON/OFF information and
prediction direction information of AC prediction, and the second
intra-frame prediction information 309b includes only the ON/OFF
information of AC prediction, as in the conventional image coding
apparatus 200c. That is, unlike the first intra-frame prediction
information 309a used for scan control in the image coding
apparatus, the second intra-frame prediction information 309b
transmitted to the decoding side includes no prediction direction
information. Accordingly, even when a prediction method is changed,
it is not required to change the content of the second intra-frame
prediction information 309b to be output to the decoding side,
thereby easily dealing with the changed prediction method. However,
the second intra-frame prediction information 309b may include not
only the ON/OFF information of AC prediction but the prediction
direction information, like the first intra-frame prediction
information 309a.
Although in the eleventh embodiment of the invention, a description
is given of coding of an interlaced image signal, a digital image
signal to be subjected to coding is not limited thereto. For
example, in an image coding apparatus in which, in coding a
progressive image, switching is performed between frame DCT
processing and field DCT processing according to the content of the
image, the efficiency of variable-length coding in coding a
progressive image can be improved using a construction similar to
the construction according to the eleventh embodiment.
Although in the eleventh embodiment of the invention, the scanner
199k3 (3) and the scanner 199k4 (4) perform different scans which
give a priority to a vertical direction, both the scanners may
perform a scan which gives a priority to a vertical direction in
the order shown in FIG. 31(c).
[Embodiment 12]
FIG. 37 is a block diagram illustrating a construction of an image
processing apparatus according to a twelfth embodiment of the
present invention. In FIG. 37, reference numeral 100m designates
the image processing apparatus (image decoding apparatus) according
to the twelfth embodiment of the invention, which decodes a coded
image signal that has been coded in the image coding apparatus
100k.
This image decoding apparatus 100m consists of a variable-length
decoding (VLD) unit 201, an inverse scanning unit 100m1, a
prediction unit 100m2, an information source decoding unit 100m3,
and an inverse blocking unit 205. The variable-length decoding
(VLD) unit 201 is for performing variable-length decoding to a
coded image signal 1006. The inverse scanning unit 100m1 is for
performing an inverse scan to quantized values 1005 which are
obtained by decoding so that the order of the quantized values 1005
is returned to the order before rearrangement in coding. The
prediction unit 100m2 is for adding quantized values (intra-frame
predicted values) 303 of a decoding target block which are
predicted from quantized values of an already decoded block in the
vicinity of the decoding target block, to quantized values 302
corresponding to the decoding target block which have been
subjected to inverse scanning. The information source decoding unit
100m3 is for performing information source decoding to quantized
values 1004 as an output of the prediction unit 100m2. The inverse
blocking unit 205 is for inverse-blocking image signals (plural
pixel values) 103 as outputs of the information source decoding
unit 100m3, on the basis of DCT type information 114 from the image
coding apparatus 100k, thereby regenerating an image signal 101
corresponding to one frame screen.
In the twelfth embodiment of the invention, the information source
decoding unit 100m3 has the same construction as the information
source decoding unit 200f1 in the conventional image decoding
apparatus 200f shown in FIG. 34, and the prediction unit 100m2 has
the same construction as the prediction unit 200d2 in the
conventional image decoding apparatus 200d shown in FIG. 32.
The inverse scanning unit 100m1 according to the twelfth embodiment
of the invention is constructed so as to return quantized values
which have been rearranged on the basis of first intra-frame
prediction information 309a, inter-frame prediction information
1015, and a scan mode switching signal 1201 in the scanning unit
100k3 in the image coding apparatus 100k according to the eleventh
embodiment, to the original order. That is, the inverse scanning
unit 100m1 consists of n pieces of inverse scanners
292m1.about.292mn each performing rearrangement for returning
quantized values which have been scanned by the scanners
199k.about.199kn in the scanning unit 100k3, to the original order.
Further, the inverse scanning unit 100m1 consists of a first switch
108b for selecting one of the inverse scanners 292m1.about.292mn on
the basis of a control signal 116m and supplying the output 1005 of
the VLD unit 201 to the selected inverse scanner, a second switch
110b for selecting one of the inverse scanners 292m1.about.292mn on
the basis of the control signal 116m and supplying the output 302
of the selected inverse scanner to the prediction unit 100m2, and
an inverse scan control unit 1501m for generating the control
signal 116m on the basis of the parameter 1015 concerning
prediction from the image coding apparatus 100k and the scan mode
switching signal 1201 from the outside.
Herein, the inverse scanners 292m1.about.292mn correspond to the
scanners 199k1.about.199kn in the image coding apparatus 100k,
respectively. More specifically,, the inverse scanner 292m1 (1) is
constituted by the respective elements 108d, 110d,
202s1.about.202s3 and 1401d in the inverse scanning unit 200d1
shown in FIG. 32. That is, the inverse scanner (1) selects one of
the inverse scanners 202s1.about.202s3 constituting the inverse
scanner (1) on the basis of control prediction information 309a'
corresponding to the first intra-frame prediction information 309a
concerning generation of intra-frame predicted values for an
intra-coded block. In addition, one of the inverse scanners
202s1.about.202s3 constituting the inverse scanner (1) performs an
inverse scan corresponding to a zigzag scan of quantized values in
the order shown in FIG. 31(a). The inverse scanner 292m2 (2)
performs an inverse scan corresponding to a zigzag scan in the
order shown in FIG. 31(a). The inverse scanner 292m3 (3) performs
an inverse scan corresponding to a scan which gives a priority to a
vertical direction in the order shown in FIG. 31(c). The inverse
scanner 292m4 (4) performs an inverse scan corresponding to a scan
which gives a priority to a vertical direction in the order
different from the order shown in FIG. 31(c).
A description is given of the operation.
In the image decoding apparatus 100m, inverse converting processes
corresponding to the respective converting processes in the image
coding apparatus 100k shown in FIG. 35 are carried out to a coded
image signal, in the reverse order of the order in coding, thereby
accurately decoding the coded image signal.
More specifically, the VLD unit 201 converts a coded image signal
1006 into quantized values 1005 by variable-length decoding. Then,
in the inverse scanning unit 100m1, the quantized values 1005 are
subjected to inverse scanning.
A processing method by the inverse scan control unit 1501m in the
inverse scanning unit 100m1 is described using a flowchart shown in
FIG. 38.
In step 1901, the inverse scan control unit 1501m decides whether
the decoding target block is subjected to intra coding or inter
coding, on the basis of inter-frame prediction information 1015
concerning generation of predicted values in inter-frame predictive
decoding of the decoding target block. As the result of the
decision, when the decoding target block is an intra-coded block,
decision of a scan mode switching signal 1201 is performed (step
1902). As the result of the decision at step 1902, when the scan
mode switching signal 1201 is in the OFF state, the inverse scan
control unit 1501m outputs the control signal 116m for selecting
the inverse scanner 292m1 (1) (step 1904). Thereby, the inverse
scanner (1) executes inverse scanning corresponding to adaptive
scanning for the quantized values 1005 corresponding to the
intra-coded block, according to control prediction information
309a' which is generated in the predictor 401 on the basis of
second intra-frame prediction information 309b from the image
coding apparatus 100k.
On the other hand, when the scan mode switching signal 1201 is in
the ON state, the inverse scan control unit 1501m outputs the
control signal 116m for selecting the inverse scanner 202m3 (3)
(step 1905). Thereby, the inverse scanner (3) executes inverse
scanning corresponding to scanning which gives a priority to a
vertical direction, for the quantized values 1005 corresponding to
the intra-coded block.
As the result of the decision at step 1901, when the decoding
target block is an inter-coded block, decision of the scan mode
switching signal 1201 is performed (step 1903). As the result of
the decision at step 1903, when the scan mode switching signal 1201
is in the OFF state, the inverse scan control unit 1501m outputs
the control signal 116m for selecting the inverse scanner 292m2 (2)
(step 1906). Thereby, the inverse scanner (2) executes inverse
scanning corresponding to zigzag scanning for the quantized values
1005 corresponding to the inter-coded block.
On the other hand, when the scan mode switching signal 1201 is in
the ON state, the inverse scan control unit 1501m outputs the
control signal 116m for selecting the inverse scanner 292m4 (4)
(step 1907). Thereby, the inverse scanner (4) executes inverse
scanning corresponding to scanning which gives a priority to a
vertical direction different from the vertical direction of the
inverse scanner (3), for the quantized values 1005 corresponding to
the inter-coded block.
Next, the prediction unit 100m2 adds quantized values 302 as an
output of the inverse scanning unit 100m1 to intra-frame predicted
values 303 of the quantized values 302, and outputs the result of
the addition 1004 to the information source decoding unit 100m3. At
this time, in the prediction unit 100m2, the above-mentioned
intra-frame predicted values 303 are generated on the basis of the
result of addition 1004 of an already decoded block and the second
intra-frame prediction information 309b from the image coding
apparatus 100k, using the method which has been described in FIG.
30.
Then, in the information source decoding unit 100m3, decoding is
carried out to the quantized values 1004 as the output of the
prediction unit 100m2. Specifically, the inverse quantization unit
203 converts the quantized values 1004 into DCT coefficients 1003
by inverse quantization. The inverse DCT unit 204 transforms the
DCT coefficients 1003 into difference signals 1002 by inverse DCT.
The adder 1101 adds inter-frame predicted values 1008 of the
difference signals 1002 to the difference signals 1002, to convert
the difference signals 1002 into an image signal (plural pixel
values) 103. At this time, the image signal 103 is stored in the
frame memory 1014. In the predictor 1102, the above-mentioned
inter-frame predicted values 1008 are generated on the basis of an
image signal 1013 of an already decoded block which is stored in
the frame memory 1014 and the prediction parameter 1015 from the
image coding apparatus 100k.
Finally, the inverse blocking unit 205 inverse-blocks the image
signals 103 according to DCT type information 114 from the image
coding apparatus 100k, thereby regenerating an image signal 101
corresponding to one frame screen.
In the image decoding apparatus 100m thus constructed, in decoding
of a coded image signal which is obtained by coding an interlaced
image signal, switching is performed between a first decoding mode
and a second decoding mode according to a scan mode switching
signal, wherein the first decoding mode comprises performing an
inverse scan corresponding to an adaptive scan to quantized values
of an intra-coded block, and performing an inverse scan
corresponding to a zigzag scan to quantized values of an
inter-coded block, and the second decoding mode comprises
performing an inverse scan corresponding to a scan which gives a
priority to a first vertical direction, to the quantized values of
the intra-coded block, and performing an inverse scan corresponding
to a scan which gives a priority to a second vertical direction, to
the quantized values of the inter-coded block. Therefore, decoding
can be accurately carried out to a coded image signal that is
obtained by performing highly efficient coding of an interlaced
image signal in which inter-coded blocks and intra-coded blocks
having different frequency component distributions coexist, with
changing a scan method.
In addition, although in the twelfth embodiment of the invention, a
description is given of decoding of an interlaced image signal, a
digital image signal to be subjected to decoding is not limited
thereto. For example, in an image decoding apparatus corresponding
to an image coding apparatus in which, in coding a progressive
image, switching is performed between frame DCT processing and
field DCT processing according to the content of the image,
decoding can be accurately carried out to a coded image signal that
is obtained by coding a progressive image signal at high coding
efficiency, using a construction similar to the construction
according to the twelfth embodiment.
In the image decoding apparatus 100m according to the twelfth
embodiment of the invention, the control prediction information
309a' corresponding to the first intra-frame prediction information
309a includes ON/OFF information and prediction direction
information of AC prediction, and the second intra-frame prediction
information 309b from the image coding apparatus 100k includes only
the ON/OFF information of AC prediction, as in the conventional
image decoding apparatus 200d. That is, unlike the control
prediction information 309a' used for scan control in the image
decoding apparatus, the second intra-frame prediction information
309b transmitted to the decoding side includes no prediction
direction information. Accordingly, even when a prediction method
is changed, it is not required to change the content of the second
intra-frame prediction information 309b to be input to the decoding
side, thereby easily dealing with the changed prediction method.
However, the second intra-frame prediction information 309b may
include not only the ON/OFF information of AC prediction but the
prediction direction information, like the control prediction
information 309a'.
Although in the twelfth embodiment of the invention, the inverse
scanner 292m3 (3) and the inverse scanner 292m4 (4) perform
different inverse scans corresponding to scans which give a
priority to a vertical direction, both the inverse scanners may
perform an inverse scan corresponding to a scan which gives a
priority to a vertical direction in the order shown in FIG.
31(c).
[Embodiment 13]
Coding or decoding programs for implementing the image processes by
the image processing apparatuses described in the aforementioned
embodiments are recorded on data recording media such as floppy
disks, whereby the processes according to these embodiments can be
easily executed in individual computer systems.
FIG. 25 is a diagram for explaining a case where an image coding or
image decoding process according to any of the aforementioned
embodiments is executed in a computer system using a floppy disk in
which the coding or decoding program is contained.
FIG. 25 shows a front view of a floppy disk FD, and a floppy disk
body D as a magnetic recording medium. The floppy disk FD is
contained in a case F. Plural tracks are concentrically formed on
the surface of the disk body D from the outer circumference toward
the inner circumference. Each track is divided into 16 sectors in
the angular direction. Therefore, in the floppy disk containing the
above-mentioned program, in a region allocated on the floppy disk
body D, data as the program is recorded.
* * * * *