U.S. patent number RE44,663 [Application Number 10/835,582] was granted by the patent office on 2013-12-24 for image decoding apparatus for persistently storing reference images.
This patent grant is currently assigned to Mitsubishi Denki Kabushiki Kaisha. The grantee listed for this patent is Kohtaro Asai, Takahiro Fukuhara, Tokumichi Murakami, Shunichi Sekiguchi. Invention is credited to Kohtaro Asai, Takahiro Fukuhara, Tokumichi Murakami, Shunichi Sekiguchi.
United States Patent |
RE44,663 |
Fukuhara , et al. |
December 24, 2013 |
Image decoding apparatus for persistently storing reference
images
Abstract
An image coding apparatus which includes a frame memory
selecting unit (35) for selecting, in response to a selection
signal, an image to be continuously stored in a plurality of frame
memories (9, 10) as a background image and storing the background
image into the plurality of frame memories (9, 10), and a
background motion compensating unit (14, 39) for performing motion
compensating prediction corresponding to an input image based on
the background image to generate a predicted image based on the
motion compensating prediction, and an image decoding apparatus
corresponding to the image coding apparatus.
Inventors: |
Fukuhara; Takahiro (Tokyo,
JP), Sekiguchi; Shunichi (Tokyo, JP), Asai;
Kohtaro (Tokyo, JP), Murakami; Tokumichi (Tokyo,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Fukuhara; Takahiro
Sekiguchi; Shunichi
Asai; Kohtaro
Murakami; Tokumichi |
Tokyo
Tokyo
Tokyo
Tokyo |
N/A
N/A
N/A
N/A |
JP
JP
JP
JP |
|
|
Assignee: |
Mitsubishi Denki Kabushiki
Kaisha (Tokyo, JP)
|
Family
ID: |
15887484 |
Appl.
No.: |
10/835,582 |
Filed: |
April 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
08759834 |
Dec 4, 1996 |
6381275 |
Apr 30, 2002 |
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Foreign Application Priority Data
|
|
|
|
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Jun 28, 1996 [JP] |
|
|
8-169489 |
|
Current U.S.
Class: |
375/240.08 |
Current CPC
Class: |
H04N
19/587 (20141101); H04N 19/00 (20130101); H04N
19/23 (20141101); H04N 19/503 (20141101); H04N
19/423 (20141101); H04N 19/59 (20141101); H04N
19/577 (20141101); H04N 19/61 (20141101) |
Current International
Class: |
H04N
7/12 (20060101) |
Field of
Search: |
;375/240.01,240.06,240.14,240.08 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
ISO/IEC JTC1/SC29/WG11 MPEG96/0653, "Background Mosaicking," F.
Dufaux, Jan. 1996, pp. 1-9, XP001150630. cited by applicant .
ISO/IEC JTC1/SC29/WG11, "MPEG95/0340: Proposal of Video Coding for
MPEG-4," K. Asai et al., Nov. 1995, pp. 1-38, XP002326903. cited by
applicant .
Proceedings of the SPIE, SPIE, Bellingham, VA, USA, vol. 2308, No.
Part 3, "Improved Image Segmentation Techniques for Hybrid
Waveform/Object-Oriented Coding," P. Kauff et al., Sep. 25, 1994,
pp. 1987-1998, XP001108933, ISSN: 0277-786X. cited by applicant
.
Wang, John Y. A.; "Applying Mid-level Vision Techniques for Video
Data Compression and Manipulation", XP000602741. cited by applicant
.
Kohtaro Asai et al., Core Experiments of Video coding with
Block-Partitioning and Adaptive Selection of Two Frame Memories
(STFM/LTFM), ISO/IEC JTC1/SC29/WG11, Jan. 1996, Munich. cited by
applicant .
"Moving Picture Information Engineering and Broadcasting
Technology", pp. 29-60, Apr. 1995, Japan Television Society. cited
by applicant .
Information Technology-Generic Coding of Moving Pictures and
Associated Audio Information: Video, Recommendation ITU-t H. 262,
ISO/IEC 13818-2, Draft International Standard, International
Organization for Standarisation, Nov. 9, 1994. cited by
applicant.
|
Primary Examiner: Lee; Young
Attorney, Agent or Firm: Birch, Stweart, Kolasch &
Birch, LLP
Claims
What is claimed is:
.[.1. An image coding apparatus, comprising: frame memories for
storing a plurality of decoded images; motion compensating
prediction means for performing motion compensating prediction
corresponding to an input image based on the plurality of decoded
images stored in said frame memories to produce a motion vector and
for generating a predicted image based on the motion compensating
prediction; prediction error calculation means for calculating a
difference between the predicted image generated by said motion
compensating prediction means and the input image to calculate a
prediction error image; decoding means for generating the decoded
images from the prediction error image calculated by said
prediction error calculation means and the predicted image; image
storage controller for determining and outputting the coding mode
of the image to be predicted according to an input control signal,
and allocating the type of the reference image to be stored in one
of said frame memories to continuously decoded image or the
stationary background image based on the selected coding mode of
the image to be predicted; and background motion compensation means
for performing motion compensating prediction corresponding to the
input image based on the background image to generate a motion
vector and generating a predicted image based on the motion
compensating prediction, wherein said image storage controller
performs re-writing of image contents into said frame memories in
response to a given control signal..].
.[.2. An image coding apparatus according to claim 1, wherein said
frame memories includes a frame memory for storing a decoded image,
and another frame memory for storing the background image..].
.[.3. An image coding apparatus according to claim 1, wherein
re-writing of image contents into said storage means by said
background image storage control means is performed in units of a
picture after a predetermined interval of time or in response to a
control signal from the outside..].
.[.4. An image coding apparatus according to claim 1, wherein
re-writing of image contents into said storage means by said
background image storage control means is performed in units of a
macroblock after a predetermined interval of time or in response to
a control signal from the outside..].
.[.5. An image coding apparatus according to claim 1, wherein said
background motion compensation means has a variable searching range
for a motion vector from the background images..].
.[.6. An image coding apparatus according to claim 1, further
comprising differential vector generation means for holding a
motion vector obtained from said motion compensation means or said
background motion compensation means and calculating a difference
vector between the generated motion vector and the motion vector in
the past, and the difference vector is variable length
coded..].
.[.7. An image coding apparatus according to claim 1, wherein said
background image storage control means performs re-writing of image
contents into said storage means per unit of a picture after a
predetermined time-interval..].
.[.8. An image coding apparatus according to claim 1, wherein said
background image storage control means performs re-writing of image
contents into said storage means per unit of a macro-block after a
predetermined time-interval..].
.[.9. An image coding apparatus according to claim 1, wherein said
background image storage control means performs re-writing of image
contents into said storage means per unit of a picture in response
to an outside control signal..].
.[.10. An image coding apparatus according to claim 1, wherein said
background image storage control means performs re-writing of image
contents into said storage means per unit of a macro-block in
response to an outside control signal..].
.[.11. An image decoding apparatus, comprising: frame memories for
storing a plurality of decoded images; motion compensation means
for performing motion compensating prediction based on the decoded
images stored in said frame memories to generate a motion
compensated image; decoding means for generating coded images from
the motion compensated image from said motion compensation means
and a prediction error image; an image storage controller for
allocating the type of the reference image to be stored in one of
said frame memories to continuously decoded image or the stationary
background image based on the coding mode of the image to be
decoded, which is extracted from encoded bitstream; and background
predicted image generation means for generating a background
predicted image based on the background image, wherein said image
storage controller performs re-writing of image contents into said
frame memories in response to a given control signal..].
.[.12. An image decoding apparatus according to claim 11, wherein
said frame memories includes a frame memory for storing a decoded
image, and another frame memory for storing the background
image..].
.[.13. An image decoding apparatus according to claim 11, wherein
re-writing of image contents into said storage means by said
background image storage control means is performed in units of a
picture after a predetermined interval of time or in response to a
control signal from the outside..].
.[.14. An image decoding apparatus according to claim 11, wherein
re-writing of image contents into said storage means by said
background image storage control means is performed in units of a
macroblock after a predetermined interval of time or in response to
a control signal from the outside..].
.[.15. An image decoding apparatus according to claim 11, further
comprising a motion vector adding unit for holding a motion vector
decoded in the past and adding the motion vector decoded in the
past to a difference vector to regenerate a motion vector..].
.[.16. An image coding apparatus according to claim 11, wherein
said background image storage control means performs re-writing of
image contents into said storage means per unit of a picture after
a predetermined time-interval..].
.[.17. An image coding apparatus according to claim 11, wherein
said background image storage control means performs re-writing of
image contents into said storage means per unit of a macro-block
after a predetermined time-interval..].
.[.18. An image coding apparatus according to claim 11, wherein
said background image storage control means performs re-writing of
image contents into said storage means per unit of a picture in
response to an outside control signal..].
.[.19. An image coding apparatus according to claim 11, wherein
said background image storage control means performs re-writing of
image contents into said storage means per unit of a macro-block in
response to an outside control signal..].
.[.20. An image coding/decoding apparatus, comprising: an image
coding apparatus, including, image coding frame memories for
storing a plurality of decoded images; image coding motion
compensating prediction means for performing motion compensating
prediction corresponding to an input image based on the plurality
of decoded images stored in said image coding frame memories to
produce a motion vector and for generating a predicted image based
on the motion compensating prediction; image coding prediction
error calculation means for calculating a difference between the
predicted image generated by said image coding motion compensating
prediction means and the input image to calculate a prediction
error image; first decoding means for generating the decoded images
from the prediction error image calculated by said image coding
prediction error calculation means and the predicted image; an
image coding image storage controller for determining and
outputting the coding mode of the image to be predicted according
to an input control signal, and allocating the type of the
reference image to be stored in one of said image coding frame
memories to continuously decoded image or the stationary background
image based on the selected coding mode of the image to be
predicted; and image coding background motion compensation means
for performing motion compensating prediction corresponding to the
input image based on the background image to generate a motion
vector and generating a predicted image based on the motion
compensating prediction; and an image decoding apparatus,
including, image decoding frame memories for storing a plurality of
decoded images; image decoding motion compensation means for
performing motion compensating prediction based on the decoded
images stored in said image decoding frame memories to generate a
motion compensated image; second decoding means for generating
coded images from the motion compensated image from said image
decoding motion compensation means and a prediction error image; an
image decoding image storage controller for allocating the type of
the reference image to be stored in one of said image decoding
frame memories to continuously decoded image or the stationary
background image based on the coding mode of the image to be
decoded, which is extracted from encoded bitstream; and image
decoding background predicted image generation means for generating
a background predicted image based on the background image, wherein
said image decoding image storage controller performs re-writing of
image contents into said image decoding frame memories in response
to a given control signal..].
.Iadd.21. An image decoding apparatus, comprising: frame memories
for storing a plurality of decoded images; motion compensation
means for performing motion compensating prediction based on the
decoded images stored in said frame memories to generate a motion
compensated image; decoding means for generating decoded images
from the motion compensated image from said motion compensation
means and a prediction error image; an image storage controller for
allocating a type of a reference image to be stored in one of said
frame memories to continuously decoded image or a stationary
background image based on a coding mode of the image to be decoded,
which is extracted from encoded bitstream; and background predicted
image generation means for generating a background predicted image
based on the stationary background image, wherein said image
storage controller performs re-writing of image contents into said
frame memories in response to a given control signal..Iaddend.
Description
.Iadd.More than one reissue application has been filed for the
reissue of U.S. Pat. No. 6,381,275. The reissue applications are
application Ser. Nos. 10/835,582 (the present application),
11/826,820, and 12/651,851, all of which are divisional reissues of
U.S. Pat. No. 6,381,275..Iaddend.
.Iadd.This application is a Reissue Application of U.S. Pat. No.
6,381,275 B1, issued on Apr. 30, 2002..Iaddend.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image coding apparatus and an image
decoding apparatus for use with a system which performs high
efficiency coding or decoding of moving pictures to perform
efficient transmission or storage of images, and more particularly
to an image coding apparatus and an image decoding apparatus which
can be applied to processing of, for example, a digital
broadcasting system which is performed using a satellite or a
ground wave or cable communication network, a digital video disk, a
mobile video phone, a PHS video phone or a data base for
images.
2. Description of the Prior Art
As a representative one of conventional high efficiency coding
systems, the MPEG2 is known which is an international standard
system recommended by the ISO/IEC/JTC1/SC29/WG11. For example,
"Image Information Engineering and Broadcasting Techniques",
Journal of the Television Engineering Society of Japan, April, 1995
explains the MPEG as a theme of special editing. A coding system of
the MPEG2 is disclosed in "3-2 Video Compression" of the same
document, pp. 29-60.
The coding system of the MPEG2 is described below.
FIG. 31 is a block diagram showing a basic construction of an
ordinary encoder of the MPEG2, and FIG. 32 is a block diagram
showing a basic construction of an MPEG2 decoder. Referring to
FIGS. 31 and 32, reference numeral 1 denotes a frame re-arranging
unit, 2 a subtracting unit, reference characters 3a and 3b denote
each an inter(interframe)/intra(intraframe) switching selector,
reference numeral 4 denotes a converting unit, 5 a quantizing unit,
6 a reverse quantizing unit, 7 a reverse converting unit, 8 an
adder, 9 a first frame memory, 10 a second frame memory, 11 a
forward direction motion compensating unit, 12 a bidirection motion
compensating unit, 13 a backward direction motion compensating
unit, 151 a motion estimating unit, 16 a coding control unit, 17 a
variable length coding unit, and 18 a buffer.
Further, reference numeral 100 denotes input image data in the form
of digital data, 101 re-arranged input image data, 102 a predictive
error image, 103 an original input image or predictive error image,
104 a conversion coefficient, 105 a quantization coefficient, 106 a
reverse quantized conversion coefficient, 107 reversed converted
image data, 108 a locally decoded image, 109 a reference image from
the first frame memory, 110 a reference image from the second frame
memory, 111 a forward direction motion predicted image, 112 a
bidirection motion predicted image, 113 a backward direction motion
predicted image, 115 a determined predicted image, 117 a control
signal to the selector, 118 a control signal to the converting unit
4, 119 an adaptive quantization value, 120 a variable length coder,
121 a bit stream, 123 a motion vector, 124 a reference image, and
125 an intra/inter switching signal.
Operation of the conventional image encoder is described below with
reference to FIG. 31.
First, an input image signal 100 in the form of a digital signal is
inputted to the frame re-arranging unit 1, by which picture frames
to be coded are re-arranged.
FIG. 33 illustrates such re-arrangement. Referring to FIG. 33,
reference character I denotes an intra (intraframe) coded picture,
P an interframe coded picture, and B a bidirectional predictive
coded picture. It is to be noted that reference numerals 1 to 10
represent an order in time in which they are displayed.
The first frame is first coded as an I picture, and then the fourth
frame is coded as a P picture, whereupon the already coded I
picture is used as a reference frame for prediction.
Then, the second frame is coded as a B picture. Thereupon, the I
picture of the first frame and the P picture of the fourth frame
coded already are used as reference frames for the prediction. In
FIG. 33, each arrow mark represents a direction in which prediction
is performed.
Thereafter, coding is performed in the construction of I, B, B, P,
B, B, P, . . . by similar processing. Accordingly, the action of
the frame re-arranging unit 1 is to re-arrange the input image
signal 100, in which the picture frames are arranged in order of
time, so that they appear in order of coding in order to allow the
processing described above.
Subsequently, since predictive coding is not performed for the I
picture mentioned above, when the re-arranged image 101 is inputted
as it is to the selector 3a, it is transmitted as a selector output
103 to the converting unit 4. On the other hand, for predictive
coding for the P picture or the B picture mentioned above, the
re-arranged image 101 is subtracted from a predicted image 115 by
the subtracting unit 2, and a predictive error image 102 is
transmitted as the selector output 103 to the converting unit
4.
Then, the selector output 103 is inputted to the converting unit 4,
and a conversion coefficient 104 is outputted from the converting
unit 4. The conversion coefficient 104 passes the quantizing unit
5, and a quantization coefficient 105 is obtained from the
quantizing unit 5. The quantization coefficient 105 is coded into a
variable length code by the variable length coding unit 17, and a
variable length coded word 120 is outputted from the variable
length coding unit 17.
The quantization coefficient 105 is, on the other hand, inputted to
the reverse quantizing unit 6, and a quantization coefficient 106
is outputted from the reverse quantizing unit 6.
Further, the quantization coefficient 106 is reverse converted back
to an image level by the reverse converting unit 7, and image data
107 is outputted from the reverse converting unit 7. The image data
107 is, where it is data of the I picture, added to a predicted
image 116 selected by the adding unit 8, and a locally decoded
image 108 is outputted from the adding unit 8.
It is to be noted that the locally decoded image 108 is written as
it is into the first frame memory 9 when it is an I picture, but,
when it is a P picture, it is written into the second frame memory
10.
On the other hand, when the locally decoded image 108 is a B
picture, it is written into neither the first frame memory 9 nor
the second frame memory 10.
Thereafter, when the locally decoded image 108 is a P picture,
since it is used only for forward direction prediction, a reference
image 124 in the first frame memory 9 is read out, and motion
prediction is performed for each macroblock (basic unit for
processing of 16 pixels.times.16 lines) by the motion estimating
unit 151. The motion estimating unit 151 thus selects one of the
macroblocks which has a value nearest to that of the current
macroblock as a predicted image, and simultaneously outputs a
motion vector 123 therefrom.
The motion vector 123 is inputted to the motion compensating units
11, 12 and 13 surrounded by a dotted line in FIG. 31, and motion
predictive pictures are outputted from the motion compensating
units 11, 12 and 13.
In this instance, the forward direction motion compensating unit 11
produces a forward direction motion predicted image 111 using a
reference image 109 from the first frame memory 9 and outputs a
thus determined predicted image 115.
Further, as described hereinabove, the locally decoded images 108
of all macroblocks in a P picture are written into the second frame
memory. However, even with the P picture mentioned above, when the
macroblocks thereof are intraframe (intra) coded, the frame
re-arranged image 101 is outputted directly as the selector
output.
Meanwhile, for a B picture, the procedure of coding processing is
similar to that for a P picture described above, but different from
the processing for a P picture, in that two reference frames are
used for prediction.
The motion estimating unit 151 performs forward direction
prediction using the reference image 109 from the first frame
memory 9, backward direction prediction using a reference image 110
from the second frame memory 10, and bidirection prediction using
both of the reference images 109 and 110 to select one of the
prediction modes with which a value nearest to that of the current
macroblock is obtained, and then outputs a motion vector 123.
In accordance with the thus determined prediction mode, in the
motion compensating unit, one of the motion compensating units 11,
12 and 13 which corresponds to the determined prediction mode
produces and outputs a predicted picture.
For example, when bidirection motion prediction is selected, the
bidirection motion compensating unit 12 produces and outputs a
predicted image 115 determined using a bidirection predicted image
112.
After coding of the B pictures of the second and third frames shown
in FIG. 33 is completed, image data written in the second frame
memory is transferred to the first frame memory. Thereafter, the P
picture of the seventh frame is coded, and a decoded picture is
written into the second frame memory.
Thereafter, B pictures (fifth and sixth frames) are coded by
similar processing to that described above.
When the macroblocks are intraframe (intra) coded, the image 101
after frame re-arrangement is directly outputted as the selector
output similarly as in the case of a P picture.
FIG. 32 is a block diagram of a conventional decoder. Referring to
FIG. 32, reference character 22 denotes a variable length decoding
unit, 107(a) an intra (intraframe) coded picture, and 107(b) a
prediction error picture.
Subsequently, operation of the conventional decoder will be
described.
A bit stream 121 is stored for a certain period of time into the
receiving buffer 18, and a variable length coded word 120 is
variable length decoded by the variable length decoding unit 22 and
outputted as a quantization coefficient 105.
The processing procedure after this is quite similar to the local
decoding processing of the encoder described hereinabove.
When the macroblock is intra decoded, a reverse converted image 107
makes an image 107(a) without passing the adding unit 8, but when
the macroblock is inter (interframe) decoded, the reverse converted
image data 107 makes an image 107(b). The image 107(b) is added to
a predicted image 115 by the adding unit 8, and a decoded image 108
is outputted from the adding unit 8. The decoded image 108 is
processed by the displayed frame re-arranging unit 38 such that
such decoded images are re-arranged so that they appear in order of
time, and finally, an output image 137 is outputted the displayed
frame re-arranging unit 38.
The example of a conventional image coder and image decoder
described above is a representative apparatus of a type which
performs forward direction, bidirection and backward direction
prediction coding in combination.
In the example, for coding of a P picture, only forward direction
prediction is performed using the first frame memory to perform
predictive coding. On the other hand, for coding of a B picture,
one of the modes of forward direction prediction, backward
direction prediction and bidirection prediction with which a
minimum predictive error is provided is selected using the first
and second frame memories.
Accordingly, as coding processing proceeds, decoded pictures
written in the frame memories are erased. Consequently, for
example, even if one of coded pictures processed in the past is
similar to a picture of the currently coded frame, since the past
decoded pictures have already been erased from the frame memories,
the similar coded picture cannot be used for reference, resulting
in a problem of lower image processing efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide, in order to
solve the problems of the conventional image encoder and image
decoder described above, an image coding apparatus and an image
decoding apparatus wherein a decoded image obtained in the past can
be utilized efficiently as a reference picture and the overall
prediction efficiency is improved to achieve moving picture coding
and decoding of a high efficiency.
According to an aspect of the present invention, there is provided
an image coding apparatus, comprising storage means for storing a
plurality of decoded images, motion compensating prediction means
for performing motion compensating prediction corresponding to an
input image based on the plurality of decoded images stored in the
storage means to produce a motion vector and for generating a
predicted image based on the motion compensating prediction,
prediction error calculation means for calculating a difference
between the predicted image generated by the motion compensating
prediction means and the input image to calculate a prediction
error image, decoding means for generating the decoded images from
the prediction error image calculated by the prediction error
calculation means and the predicted image, background image storage
control means for selecting one of the decoded images which is to
be continuously stored in the storage means as a background image
and storing the background image into the storage means, and
background motion compensation means for performing motion
compensating prediction corresponding to the input image based on
the background image to generate a motion vector and generating a
predicted image based on the motion compensating prediction.
According to another aspect of the present invention, there is
provided an image decoding apparatus, comprising storage means for
storing a plurality of decoded images, motion compensation means
for performing motion compensating prediction based on the decoded
images stored in the storage means to generate a motion compensated
image, decoding means for generating the coded images from the
motion compensated image from the motion compensation means and a
prediction error image, background image storage control means for
selecting one of the decoded images which is to be continuously
stored in the storage means as a background image and storing the
background image into the storage means, and background predicted
image generation means for generating a background predicted image
based on the background image.
The image coding apparatus and the image decoding apparatus of the
present invention may be constructed such that the storage means
includes a frame memory for storing a decoded image, and another
frame memory for storing the background image.
The image coding apparatus and the image decoding apparatus of the
present invention may otherwise be constructed such that re-writing
of image contents into the storage means by the background image
storage control means is performed in units of a picture after a
predetermined interval of time or in response to a control signal
from the outside.
The image coding apparatus and the image decoding apparatus of the
present invention may otherwise be constructed such that re-writing
of image contents into the storage means by the background image
storage control means is performed in units of a macroblock after a
predetermined interval of time or in response to a control signal
from the outside.
The image coding apparatus of the present invention may otherwise
be constructed such that the background motion compensation means
has a variable searching range for a motion vector from the
background images.
The image coding apparatus of the present invention may otherwise
be constructed such that it further comprises differential vector
generation means for holding a motion vector obtained from the
motion compensating prediction means or the background motion
compensation means and calculating a difference vector between the
generated motion vector and the motion vector in the past, and the
difference vector is variable length coded.
The image decoding apparatus of the present invention may otherwise
be constructed such that it further comprises a motion vector
adding unit for holding a motion vector decoded in the past and
adding the motion vector decoded in the past to a difference vector
to regenerate a motion vector.
According to a further aspect of the present invention, there is
provided an image decoding apparatus which outputs a coded bit
stream of moving pictures, comprising a plurality of frame memory
groups for storing, individually for a plurality of objects which
compose a screen, decoded images of the objects in the past, a
frame memory selecting unit for selecting, in response to a control
signal, into a frame memory of which one of the plurality of frame
memory groups a decoded image is to be written, a motion
compensation predicting unit for selecting one of forward direction
prediction, backward direction prediction, bidirection prediction
and background prediction in units of an object using reference
images read out from frame memories of the plurality of frame
memory groups provided for the individual objects to perform motion
compensating prediction, a subtractor for calculating a difference
between the predicted image and a current image to calculate a
prediction error image, an adding unit for adding the predicted
image from the reference images and the prediction error image of
the current image, and a variable length coding unit for variable
length coding information.
According to a still further aspect of the present invention, there
is provided an image decoding apparatus which decodes a coded bit
stream of moving pictures, comprising a plurality of frame memory
groups for storing, individually for a plurality of objects which
construct a screen, decoded images of the objects, a frame memory
selecting unit for selecting, in response to a control signal, into
a frame memory of which one of the plurality of frame memory groups
the coded images are to be written for the individual objects, a
variable length decoding unit for variable length decoding the
coded bit stream, and a motion compensating unit for selecting one
of forward direction prediction, backward direction prediction,
bidirection prediction and background prediction in units of an
object using reference images read out from frame memories of the
plurality of frame memory groups to generate a motion compensated
image.
The image coding apparatus or the image decoding apparatus of the
present invention may be constructed such that the plurality of
frame memory groups include three frame memory groups.
The image coding apparatus of the present invention may otherwise
be constructed such that re-writing of image contents of a region
in which an object which is a subject of coding is included in the
plurality of frame memory groups in which coded images of the
object in the past are stored is performed after a certain interval
of time or in response to a control signal from the outside.
The image decoding apparatus of the present invention may otherwise
be constructed such that re-writing of image contents of a region
in which an object which is a subject of decoding is included in
the plurality of frame memory groups in which coded images of the
object in the past are stored is performed after a certain interval
of time or in response to a control signal from the outside.
The image coding apparatus of the present invention may otherwise
be constructed such that searching ranges for a motion vector from
reference images from the plurality of frame memory groups for the
individual objects are variable for the individual objects.
The image coding apparatus of the present invention may otherwise
be constructed such that it further comprises differential vector
generation means for holding a motion vector in the past obtained
by referring to images from the plurality of frame memory groups
for the individual objects and calculating difference vectors
separately for the individual objects, and the difference vectors
are variable length coded.
The image decoding apparatus of the present invention may otherwise
be constructed such that it further comprises a motion vector
adding unit for holding decoded motion vectors in the past obtained
by referring to images in the plurality of frame memory groups for
the individual objects for a certain period of time and adding the
motion vectors decoded in the past to the decoded difference
vectors to regenerate motion vectors for the individual
objects.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood
accompanying drawings which are given by way of illustration only,
and thus are not limitative of the present invention, and
wherein:
FIG. 1 is a block diagram of a coding apparatus for moving pictures
according to an embodiment 1 of the present invention;
FIG. 2 is a block diagram showing an internal construction of a
motion estimating unit of the coding apparatus of the embodiment 1
of the present invention;
FIG. 3 is a block diagram showing an internal construction of a
motion compensation predicting unit of the coding apparatus of the
embodiment 1 of the present invention;
FIG. 4 is a block diagram showing another construction of the
coding apparatus for moving pictures according to the embodiment 1
of the present invention;
FIGS. 5A to 5C are diagrammatic views illustrating an example of
the relationship between patterns of pictures and prediction modes
in the embodiment 1 of the present invention;
FIG. 6 is a block diagram showing a further construction of the
coding apparatus for moving pictures according to the embodiment 1
of the present invention;
FIG. 7 is a block diagram of a decoding apparatus for moving
pictures according to an embodiment 2 of the present invention;
FIG. 8 is a block diagram of a motion compensating unit of the
decoding apparatus of the embodiment 2 of the present
invention;
FIG. 9 is a block diagram of a coding apparatus for moving pictures
according to an embodiment 3 of the present invention;
FIG. 10 is a block diagram of a motion estimating unit of the
coding apparatus in the embodiment 3 of the present invention;
FIG. 11 is a block diagram of a motion compensating unit of the
coding apparatus in the embodiment 3 of the present invention;
FIGS. 12A, 12B and 12C are diagrammatic views illustrating an
example of the relationship between picture patterns and prediction
modes in the embodiment 3 of the present invention;
FIG. 13 is a block diagram of a decoding apparatus for moving
pictures according to an embodiment 4 of the present invention;
FIG. 14 is a block diagram of a motion compensating unit of the
decoding apparatus of the embodiment 4 of the present
invention;
FIG. 15 is a diagrammatic view illustrating re-writing of a picture
in a frame memory in units of a macroblock in a coding apparatus
according to an embodiment 5 of the present invention;
FIG. 16 is a block diagram of a coding apparatus according to an
embodiment 8 of the present invention;
FIGS. 17A and 17B are diagrammatic views illustrating a coding
method of a motion vector in the embodiment 8 of the present
invention;
FIG. 18 is a block diagram showing another construction of the
coding apparatus according to the embodiment 8 of the present
invention;
FIG. 19 is a block diagram of a decoding apparatus according to an
embodiment 9 of the present invention;
FIG. 20 is a block diagram showing another construction of the
decoding apparatus according to the embodiment 9 of the present
invention;
FIG. 21 is a diagrammatic view illustrating the relationship
between pictures and objects;
FIG. 22 is a block diagram of a coding apparatus according
embodiments 10 and 15 of the present invention;
FIG. 23 is a block diagram of a decoding apparatus according to an
embodiment 11 of the present invention;
FIG. 24 is a block diagram of a coding apparatus according to
embodiments 12 and 15 of the present invention;
FIG. 25 is a block diagram of a decoding apparatus according to an
embodiment 13 of the present invention;
FIG. 26 is a diagrammatic view illustrating re-writing of an image
in an object region performed in a coding apparatus according to an
embodiment 14 of the present invention;
FIG. 27 is a diagrammatic view of a coding apparatus according to
an embodiment 16 of the present invention;
FIG. 28 is a diagrammatic view of a decoding apparatus according to
an embodiment 17 of the present invention;
FIG. 29 is a diagrammatic view of a coding apparatus according to
an embodiment 18 of the present invention;
FIG. 30 is a diagrammatic view of a decoding apparatus according to
an embodiment 19 of the present invention;
FIG. 31 is a block diagram of a conventional encoder;
FIG. 32 is a block diagram of a conventional decoder; and
FIG. 33 is a diagrammatic view showing an example of an array of
pictures.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Further scope of applicability of the present invention will become
apparent from the detailed description given hereinafter. However,
it should be understood that the detailed description and specific
examples, while indicating preferred embodiments of the invention,
are given by way of illustration only, since various changes and
modifications within the spirit and scope of the invention will
become apparent to those skilled in the art from this detailed
description.
In the following, image coding apparatus and image decoding
apparatus of preferred embodiments of the present invention will be
described with reference to the accompanying drawings.
Embodiment 1
FIG. 1 is a block diagram of a coding apparatus for moving pictures
according to an embodiment 1 of the present invention. Referring to
FIG. 1, reference numeral 21 denotes a motion compensation
predicting unit as motion compensation predicting means, 35 a frame
memory selecting unit as background image storing control means,
and 45 a multiplexing unit. Further, reference numeral 126 denotes
a determined motion prediction mode, reference numerals 134 and 135
denote each a selected decoded image, and reference numeral 139
denotes a multiplexed bit stream. Since the other components are
similar to those used in the description of the prior art shown in
FIGS. 31 to 33, they are denoted by same reference numerals and
repetitive description of them is omitted here.
Subsequently, operation will be described.
Basic coding operation is equivalent to motion compensating
prediction+conversion coding described hereinabove in connection
with the conventional example. Accordingly, only differences will
be described here.
A locally decoded image 108 is inputted to the frame memory
selecting unit 35, by which it is selected into which one of the
first frame memory 9 and the second frame memory 10 it is to be
written. Meanwhile, the motion estimating unit 15 reads out
reference images 109 and 110 from the frame memories 9 and 10 and
outputs a determined motion prediction mode 126 and a motion vector
123 with which the prediction error of the locally decoded image
108 from the re-arranged input image data 101 is minimized.
The motion compensation predicting unit 21 reads out the reference
images 109 and 110 and outputs a motion predicted image 115 based
on the determined motion prediction mode 126 and the motion vector
123.
The bit stream 121 is multiplexed together with the prediction mode
126 by the multiplexing unit 45 and forwarded from the multiplexing
unit 45.
The foregoing is the basic operation of the image coding apparatus
of the embodiment 1. In the following, details of the individual
units will be described.
FIG. 2 shows an internal construction of the motion estimating unit
15. Referring to FIG. 2, reference numeral 27 denotes a forward
direction predicted image generating unit, 28 a bidirection
predicted image generating unit, 29 a backward direction predicted
image generating unit, 30 a background predicted image generating
unit, 31 a prediction mode determining unit, 127 a forward
direction predicted image, 128 a bidirection predicted image, 129 a
backward direction predicted image, and 130 a background predicted
image.
Subsequently, operation of the motion estimating unit 15 will be
described.
Each of the predicted image generating units 27, 28, 29 and 30
generates a predicted image in accordance with a predetermined
prediction mode.
For example, the forward direction predicted image generating unit
27 reads out reference images 109 from the first frame memory 9 and
searches the reference images 109 for an image which has a value
nearest to the value of the input image data 101.
To this end, for example, a block matching method which is employed
also in the conventional example described in connection with the
prior art may be used as it is. In particular, matching is
performed for all pixels in macroblocks described above, and an
image wherein the sum total of error values exhibits a minimum
value is searched for. As a result, the forward direction predicted
image generating unit 27 outputs a forward direction predicted
image 127.
The backward direction predicted image generating unit 29 performs
searching of reference images 110 from the second frame memory 10
and then performs block matching similarly. Then, the backward
direction predicted image generating unit 29 outputs a backward
direction predicted image 129.
The bidirection predicted image generating unit 28 outputs a
bidirection predicted image 128 using the two frame memories 9 and
10. The bidirection predicted image generating unit 28 generates a
forward direction predicted image and a backward direction
predicted image separately from each other, and generates a
bidirection predicted image based on those images.
For example, a technique wherein an average image of the forward
direction predicted image and the backward direction predicted
image is obtained and determined as a bidirection predicted image
128 may be used.
Meanwhile, the background predicted image generating unit 30 reads
out a reference image 110 from the second frame memory and outputs
a background predicted image 130 by block matching.
The prediction mode determining unit 31 inputs predicted images
selected in the predicted images 127, 128, 129 and 130 and selects
a prediction mode in which the difference (prediction error) from
the input image 101 is minimized. In this instance, a prediction
mode 126 and a motion vector 123 are outputted from the prediction
mode determining unit 31. The prediction mode 126 may be determined
such that, for example, it has a value 0 for the forward direction
prediction mode, another value 1 for the backward direction
prediction mode, a further value 2 for the bidirectional prediction
mode, and a still further value 3 for the background prediction
mode.
It is to be noted that processing operation of the motion vector
123 generated by and outputted from the prediction mode determining
unit 31 of FIG. 2 is such as follows.
In particular, when searching of reference images is performed
within a predetermined range and a predicted image which exhibits a
minimum prediction error is obtained by each of the predicted image
generating units, motion vectors 123(a), 123(b), 123(c) and 123(d)
are outputted from the predicted image generating units 27 to 30
together with the predicted images, respectively. The outputs are
all inputted to the prediction mode determining unit 31, by which
one of the predicted images 127, 128, 129 and 130 which exhibits a
minimum error from the current image 101 is selected. Thus, the
motion vector (one of the motion vectors 123(a), 123(b), 123(c) and
123(d)) which provides the minimum value is finally outputted as a
motion vector 123 from the prediction mode determining unit 31.
FIG. 3 is a block diagram showing an internal construction of the
motion compensation predicting unit 21. Referring to FIG. 3,
reference numerals 24 and 26 denote each a selector (switch), and
reference numeral 114 denotes a background predicted image.
Subsequently, operation will be described. In the switch 24, two
switches SW1 and SW2 are opened or closed in accordance with the
determined motion prediction mode 126.
For example, when the prediction mode 126 outputted from the
prediction mode determining unit 31 indicates the bidirection
prediction image mode, the switch SW1 of the selector 24 selects a
node B and the switch SW2 selects another node C. On the other
hand, when the background prediction mode is selected, the switch
SW1 is OFF (provides no selection) and the switch SW2 selects a
further node E.
In the former case, the bidirection motion compensating unit 12
generates a bidirection predicted image 112 using a motion vector
123. Simultaneously, the output node from the bidirection motion
compensating unit 12 is selected by the switch 26. Consequently,
the bidirection predicted image 112 from the motion compensation
predicting unit 21 is outputted as a determined predicted image
115.
Further, while the embodiment 1 described above is constructed such
that it includes a motion estimating unit and a motion compensation
predicting unit separately from each other and a prediction mode
and a motion vector obtained by the motion estimating unit are sent
to the motion compensation predicting unit so that a predicted
image is generated by the motion compensation predicting unit, an
equivalent function can be realized even by such a construction
that the two units are replaced by a motion estimating/compensating
unit 39 as seen in FIG. 4.
By the way, in the embodiment 1 described above, similarly as in
the conventional example, coding is performed in units of a
macroblock which is a processing unit for images.
Meanwhile, in the processing of the MPEG2 of the conventional
example described in connection with the prior art, three types of
pictures including an I picture, a P picture and a B picture are
involved, and a prediction mode is restricted by those
pictures.
In particular, in an I picture, all macroblocks are intra coded,
and no prediction mode is involved. In a P picture, only forward
direction prediction is involved, and in a B picture, three
prediction modes of forward direction prediction, backward
direction prediction and bidirection prediction are involved.
In the meantime, according to the present invention, in addition to
the pictures described above, two other picture types of a PG
picture and a PBG picture, which will be hereinafter described, are
involved. In a PG picture, two prediction modes including forward
direction prediction and background prediction are involved, and in
a PBG picture, four prediction modes of forward direction
prediction, backward direction prediction, bidirection prediction
and background prediction are involved.
FIGS. 5A, 5B and 5C show examples of patterns of coded pictures.
For example, the pattern shown in FIG. 5A is similar to the
conventional example, and similar means to that to the prior art
may be applied. For the pattern shown in FIG. 5B, two prediction
modes including background prediction from a background image
(indicated at "BG" in FIG. 5B) written in the second frame memory
10 and forward direction prediction from an immediately preceding
decoded picture are involved, and one of the two prediction modes
which provides a smaller prediction error is selected.
This operation is performed up to the sixth picture, and then
beginning with the seventh picture, the picture structure changes
to the structure of P, B, B, P, . . . In this instance, up to the
sixth picture, a background image is recorded in the second frame
memory 10. Thereafter, however, the ninth picture is first forward
direction predicted referring to the sixth picture.
Then, similarly as in the conventional example, the seventh and
eighth pictures are predicted referring to decoded pictures of the
sixth picture and the ninth picture.
In FIG. 5B, a dotted line extending from the second picture to the
"BG" signifies that, for example, contents of the decoded image of
the second picture are written as a background image into the
second frame memory.
As the writing timing, writing may be performed after each certain
interval of time or in response to a control signal from the
outside. However, the pattern described above is a mere example,
and any other pattern may be available.
FIG. 5C shows a pattern wherein the first picture is an I picture,
and it can be seen that a coded picture of the I picture is written
as a background image into the second frame memory.
Then, the prediction modes of macroblocks of all pictures beginning
with the third picture are selected either to background image
prediction or to forward direction prediction. This is effective
where the background image is stationary, and is very effective
with a scene wherein some person speaks in front of the background
image since a phenomenon called occlusion wherein the background
image comes into and out of sight as movement of the person occurs.
Further, when the background image is a still picture and is known
in advance, the background image may be written into the second
frame in advance before coding processing is started.
It is to be noted that the pattern of coded pictures may take any
pattern other than those shown in FIGS. 5A, 5B and 5C.
Subsequently, operation of the frame memory selecting unit 35 shown
in FIG. 1 will be described.
In the frame memory selecting unit 35, it is determined into which
one of the first frame memory 9 and the second frame memory 10 the
locally decoded image 108 is to be written. As the determination
method, a technique may be employed wherein, for example, as seen
from another construction of the coding apparatus of the embodiment
1 shown in FIG. 6, a control signal 140 from the frame re-arranging
unit 1 is received by the frame memory selecting unit 35 and
switching between the first frame memory 9 and the second frame
memory 10 is performed in accordance with the received control
signal 140 by the frame memory selecting unit 35.
In this instance, since the types of a currently coded picture and
another picture to be coded subsequently are known, for example, a
decoded image is written into the first frame memory 9 till the
"BG" end indicated in FIG. 5B unless a signal from the outside is
received, and since the picture structure thereafter changes to the
structure of P, B, B, P, . . . , the frame memory for a subject of
writing should be selected adaptively as in the conventional
example.
Further, as seen in FIG. 5B, as writing of a background image from
a decoded picture at a certain position into the second frame
memory 10, for example, when a scene change is detected, the
decoded image may be written after a predetermined interval of
time.
For the detection method for a scene change, a technique
conventionally used may be used. For example, a method wherein, if
the number of those of macroblocks in one frame with which the
prediction error is higher than a threshold value is larger than a
certain value, then a scene change is detected.
It is a matter of course that various other techniques than that
described just above are available.
Further, while, in the image coding apparatus of the present
embodiment 1, the first and second frame memories are provided as
storage means to realize a construction for switching of motion
compensation prediction, for implementation of the hardware, a
plurality of frame memories can be provided at a time by cutting a
memory having a storage capacity for the plurality of frame
memories based on internal addresses.
As described above, with the image coding apparatus of the present
embodiment 1, since a background image is stored and motion
compensating prediction is performed using background prediction
based on the background image, coding can be performed while
keeping a high prediction efficiency without being influenced by a
coding sequence.
It is to be noted that, while storage control of a background image
into the frame memories is described in the foregoing description,
it is a matter of course that the background image here signifies
an image which is stored continuously and does not signify contents
themselves of an image.
In particular, since images which are successively updated like a
conventional picture array include some image which is effective
for later prediction, this image is continuously stored
independently of storage by the updating procedure, and here, this
image is referred to as background image.
Embodiment 2
FIG. 7 is a block diagram of a decoding apparatus for moving
pictures according to an embodiment 2 of the present invention.
Referring to FIG. 7, reference numeral 23 denotes a motion
compensating unit, and 46 a demultiplexing unit. The other
components than those are similar to those employed in the
embodiment 1, and accordingly, repetitive description of them is
omitted here.
Operation will be described subsequently.
The decoding apparatus of the present embodiment 2 corresponds to
the coding apparatus described in connection with the embodiment 1,
and a basic processing procedure for decoding thereof is similar to
that of the decoding apparatus described in the conventional
example described in the prior art. Thus, description will be given
here principally of differences between them.
A locally decoded image 108 is inputted to the frame memory
selecting unit 35. The frame memory selecting unit 35 receives the
locally decoded image 108, selects a frame memory of a subject of
writing, and transfers a selected decoded image 134 or 135 to the
first frame memory 9 and the second frame memory 10.
Then, the decoded image is written into the first frame memory 9 or
the second frame memory 10.
Meanwhile, the motion compensating unit 23 reads out reference
images 109 and 110 from the two frame memories and generates a
predicted image 115 in accordance with a predetermined motion
prediction mode 126 in a similar procedure to that in local
decoding of the coding apparatus.
FIG. 8 is a block diagram showing an internal construction of the
motion compensating unit 23. Referring to FIG. 8, reference numeral
32 denotes a switch.
Subsequently, operation will be described.
One of the predicted image generating units 27 to 30 which
corresponds to a selected prediction mode 126 reads out reference
images 109 or 110 to generate a predicted image. Further, the
switch 32 is switched in response to the selected prediction mode
so that a finally determined predicted image 115 is outputted.
Embodiment 3
FIG. 9 is a block diagram of an image coding apparatus according to
an embodiment 3 of the present invention. Referring to FIG. 9,
reference numeral 33 denotes a motion compensation predicting unit,
34 a third frame memory, 37 a frame memory selecting unit, 41 a
motion estimating unit, 133 a reference image of the third frame
memory, and 136 a selected locally decoded image. The other
components than those mentioned above are similar to those employed
in the embodiment 1, and accordingly, repetitive description of
them is omitted here.
The image coding apparatus of the present embodiment 3 is
characterized in that it includes the third frame memory in
addition to the construction of the image encoder of the embodiment
1 shown in FIG. 1.
Subsequently, operation will be described.
Reference images 109, 110 and 133 are read out from the three frame
memories 9, 10 and 34 in which coded images in the past are stored,
and motion prediction is performed by the motion estimating unit
41. A motion vector 123 and a prediction mode 126 obtained by the
motion prediction are inputted to the motion compensation
predicting unit 33.
The motion compensation predicting unit 33 selects a reference
image necessary for generation of a predetermined motion predicted
image from among the reference images 109, 110 and 133 based on the
determined prediction mode 126, and outputs the determined
predicted image 115.
Meanwhile, a locally decoded image 108 is written, after it is
determined by the frame memory selecting unit 37 into which frame
memory the locally decoded image 108 should be written, as a
reference image 134, 135 or 136 into the thus determined frame
memory.
FIG. 10 shows an internal construction of the motion estimating
unit 41. Referring to FIG. 10, reference numeral 42 denotes a
prediction mode determining unit.
The motion estimating unit 41 shown in FIG. 10 has a construction
which includes, in addition to the motion estimating unit 15 shown
in FIG. 2, a background predicted image generating unit 30 for
inputting a reference image 133 from the third frame memory.
The forward direction predicted image generating unit 27 inputs an
input image 101 and a reference image 109 of the first frame memory
and outputs a forward direction predicted image 127, and the
bidirection predicted image generating unit 28 inputs the input
image 101, the reference image 109 of the first frame memory and a
reference image 110 of the second frame memory and outputs a
bidirection predicted image 128.
The backward direction predicted image generating unit 29 inputs
the input image 101 and the reference image 110 of the second frame
memory and outputs a backward direction predicted image 129, and
the background predicted image generating unit 30 inputs the input
image 101 and a reference image 133 of the third frame memory and
outputs a background predicted image 130.
The prediction mode determining unit 42 calculates absolute value
differences between predicted images 27, 28, 29 and 30 mentioned
above and input the image 101, determines a prediction mode which
exhibits a minimum one of the absolute value differences, and
outputs the determined prediction mode as a prediction mode 126.
Simultaneously, the prediction mode determining unit 42 outputs a
motion vector 123.
FIG. 11 is a block diagram of an internal construction of the
motion compensation predicting unit 33. Referring to FIG. 11, a
switch 25 is opened or closed in response to the prediction mode
126 so that the reference image 109 or 110 is inputted to a
selected one of the motion compensating units. For example, when
the forward direction prediction mode is selected, a switch SW1 is
switched to a node A while another SW2 is switched off. However,
when the bidirection prediction mode is selected, the switch SW1 is
switched to another node B while the switch SW2 is switched to a
further node C.
When the background prediction mode is selected, a reference image
133 is inputted directly and referred to. Subsequently, in the
switch 26, the switches SW1 and SW2 are switched to nodes
corresponding to the prediction mode 126, and a predicted image 115
determined finally is outputted from the switch 26.
Further, while, in the present embodiment 3, the first, second and
third frame memories are provided to realize a construction for
switching of motion compensating prediction, for implementation of
the hardware, a plurality of frame memories can be provided at a
time by cutting a memory having a storage capacity for the
plurality of frame memories based on internal addresses.
FIGS. 12A, 12B and 12C are diagrammatic views illustrating
re-writing operation of the frame memories in the present
embodiment 3, and in the following, the re-writing operation will
be described including a relationship to the operation of the frame
memory selecting unit 37 described hereinabove with reference to
FIGS. 6A, 6B and 6C.
FIGS. 12A, 12B and 12C show three different patterns. In FIG. 12A,
PG pictures of background prediction and forward direction
prediction appear beginning with the sixth picture, and the
construction continues up to the ninth picture. Thereafter, the
structure of IBBP is restored beginning with the 10th picture.
In FIG. 12B, switching among all prediction modes of forward
direction prediction, backward direction prediction, bidirection
prediction and background prediction is possible with the first,
second, fourth, fifth, seventh, eighth, tenth and eleventh
pictures, and the prediction efficiency is highest. Further, also
in this instance, while writing as a background image into the
third frame memory is enabled at any time, in the example of FIG.
12B, writing into the third frame memory for a background image is
performed from the fifth and tenth pictures.
In FIG. 12C, PG pictures of background prediction and forward
direction prediction appear with the third, sixth, ninth and
twelfth pictures.
In those operations, since it is already known of which picture
type a currently decoded picture is, a frame memory into which the
locally decoded image 108 is to be written is determined by itself
in accordance with the picture type by the frame memory selecting
unit 37. In particular, where the pattern has the structure of
IBBP, for the I picture, the locally decoded image 108 is written
into the first frame memory, but, for the P picture, the locally
decoded image 108 is written into the second frame memory. For the
B pictures, the locally decoded image 108 is written into none of
the frame memories.
It is to be noted that, as described already, a certain decoded
image is written as a background image also into the third frame
after a certain interval of time or in response to a control signal
from the outside.
Embodiment 4
FIG. 13 is a block diagram of a decoding apparatus for moving
pictures according to an embodiment 4 of the present invention. The
decoding apparatus corresponds to the coding apparatus of the
embodiment 3 shown in FIG. 9. Referring to FIG. 13, reference
numeral 36 denotes a motion compensating unit. Of the other
components than that just mentioned, those components denoted by
the same reference numerals to those used in the embodiments 1 to 3
are similar elements, and accordingly, repetitive description of
them is omitted here.
Subsequently, operation will be described.
The motion compensating unit 36 performs motion compensation
referring to reference images 109, 110 and 133 read out from the
first frame memory 9, the second frame memory 10 and the third
frame memory 11 and outputs a predicted image 115.
Decoded images are re-arranged by the displayed frame re-arranging
unit 38 again such that they appear in order of time for
displaying, and an output image 137 is obtained as a result of the
re-arrangement.
FIG. 14 is a block diagram showing an internal construction of the
motion compensating unit 36. Referring to FIG. 14, one of predicted
images generated by the individual predicted image generating units
is selected in response to a prediction mode 126 by the switch 32.
Then, the selected predicted image 115 is outputted to the adding
unit 8.
The fourth embodiment presents similar effects to those of the
imaging coding apparatus of the embodiment 3.
Embodiment 5
While the image coding apparatus such as embodiment 1 described
above performs re-writing to a background image illustrated in
FIGS. 5B and 5C in units of a picture, it is possible to perform
prediction efficiently if writing to a background image is
performed in units of a macroblock.
As the technique for re-writing to a background image, for example,
a technique wherein updating is performed after each predetermined
interval of time in coding processing or another technique wherein,
when all pixels in a macroblock at a certain position are not
referred to for prediction for more than a certain period of time,
a control signal is generated to re-write only the macroblock in a
background image with a decoded image may be used.
FIG. 15 illustrates this. Referring to FIG. 15, at a timing for
writing from the second picture of FIG. 5B into the background
image "BG", only a macroblock in a region of slanted lines in FIG.
15 is written as it is into the second frame memory and is used as
part of a reference image for direction of the third picture.
Similarly, also where the image coding apparatus such as embodiment
3 described above includes three frame memories, re-writing into a
background image shown in FIGS. 12B and 12C is performed in units
of a macroblock. As the technique for re-writing, the same
operation as described above may be performed.
As described above, since re-writing of contents of an image in
each frame memory is performed in units of a macroblock after each
certain interval of time or in response to a control signal from
the outside, the contents of the image in the frame memory can
always be kept, at a finer level, to contents from which a high
prediction efficiency for background prediction can be
obtained.
Embodiment 6
Also an image decoding apparatus which corresponds to the image
coding apparatus of the embodiment 5 can perform re-writing to the
background image in units of a macroblock.
For example, in an image decoding apparatus shown in FIG. 7, after
a decoded image 108 is selected by the frame memory selecting unit
35, a macroblock of the background image at the same position as
that of the macroblock mentioned above is re-written to a selected
decoded image 135. It is to be noted that the updating in units of
a macroblock may be performed after a certain interval of time or
in response to a control signal from the outside.
Similarly, also in the decoding apparatus shown in FIG. 13, which
includes three frame memories, re-writing to a background image
illustrated in FIGS. 12B and 12C is performed in units of a
macroblock. As the technique for re-writing, the same operation as
described above may be performed.
Embodiment 7
It is also effective to vary the motion searching range upon
background prediction by the motion estimating unit 15 of the image
coding apparatus of the embodiment 1 shown in FIG. 1 or the motion
compensation predicting unit 33 shown in FIG. 3 to the searching
range of forward direction prediction or backward direction
prediction.
To this end, it is advisable to set, making use of the fact that,
for example, background prediction acts effectively when the motion
vector from the background is 0, the searching range to a smaller
range than that for any other prediction.
The image coding apparatus of the present embodiment 7 exhibits an
additional effect in that the searching time is reduced and that,
since codes obtained by variable length coding of motion vectors
can be set comparatively short, the coding information amount of
motion vectors can be reduced.
Embodiment 8
FIG. 16 is a block diagram of an image coding apparatus according
to an embodiment 8 of the present invention. Referring to FIG. 16,
reference numeral 47 denotes a differential vector generating unit,
and 141 a difference vector. Of the other components than those
mentioned above, those components denoted by the same reference
numerals to those used in the embodiment 1 are similar elements,
and accordingly, repetitive description of them is omitted
here.
The differential vector generating unit 47 calculates a difference
vector 141 between a current motion vector 123 and a reference
vector. Then, the difference vector 141 is variable length coded by
the variable length coding unit 17.
FIGS. 17A and 17B illustrates a coding method for a motion vector,
and particularly, FIG. 17A shows a reference motion vector for the
first frame memory 9 and FIG. 17B shows a reference motion vector
for the second frame memory 10.
Operation will be described subsequently.
Referring to FIGS. 17A and 17B, each rectangular frame denotes one
macroblock. It is known that, for a motion vector MV(1) of a
current macroblock obtained by reading out a reference image in the
first frame memory and performing motion compensating prediction of
the reference image, it is effective to actually variable length
code, using three motion vectors MV1(1), MV2(1) and MV3(1) of
already coded and decoded macroblocks as candidate vectors,
difference values of the motion vector MV(1) from them.
For example, if it is tried to use a median of the motion vectors
MV1(1), MV2(1) and MV3(1) as a candidate vector, then the
difference vector PMV(1) can be represented by the following
expression: PMV(1)=MV(1)-median (MV1(1), MV2(1), MV3(1)) where
"median" is an operator for calculation of a median.
Similarly, for the second frame memory, PMV(2)=MV(2)-median
(MV1(2), MV2(2), MV3(2))
FIG. 18 is a block diagram of an image coding apparatus which
includes a differential vector generating unit 47 in addition to
the construction of the image coding apparatus shown in FIG. 9.
For calculation of a difference vector, in addition to the
operation described above, a reference motion vector PMV(3) for the
third frame memory may be calculated and variable length coded.
The information generation amount of motion vectors can be supplied
in such a manner as described above.
Embodiment 9
FIGS. 19 and 20 are block diagrams of decoding apparatus which
correspond to the coding apparatus of the embodiment 8 described
hereinabove with reference to FIGS. 16 and 18 in which a difference
vector is used, respectively. Referring to FIGS. 19 and 20,
reference numeral 48 denotes a motion vector adding unit. The other
components are similar to those of the decoding apparatus of the
embodiment 2 shown in FIG. 7, and accordingly, repetitive
description of them is omitted here.
In the decoding apparatus of the present embodiment 9, a difference
vector 141 variable length decoded by the variable length decoding
unit 22 is added to a reference vector by the variable length
decoding unit 22 to calculate a motion vector 123.
The processing following it is the same as the operation of the
decoding apparatus of the embodiment 2 shown in FIG. 7, and
therefore, repetitive description of it is omitted here.
Embodiment 10
While, in the coding apparatus of FIG. 1, an entire screen in a
picture is used as a subject of coding, the image coding apparatus
of the present embodiment 10 is constructed such that the picture
type for coding is variable in units of one of a plurality of
subject images (objects) which construct the screen.
Referring to FIG. 21, for example, if a screen is composed of an
object 1 (fish), an object 2 (water: background picture) and an
object 3 (ball) and boundaries among them are known, then those
objects can be coded using different techniques from one
another.
In the image coding apparatus of the present embodiment 10, such
coding techniques are realized by using different picture types
from one another. For example, since the object 1 exhibits a
comparatively large amount of motion, the construction of picture
types of FIG. 5A is used for the object 1 taking it into
consideration that bidirection prediction is higher in prediction
efficiency than background prediction.
On the other hand, since the object 2 is an image which exhibits
little motion, it is effective to use background prediction for it.
Accordingly, the construction of FIG. 5C should be used. However,
if such a variation that a scene changes rapidly occurs with a
certain midst picture, then the construction which includes B
pictures beginning with the midst picture as seen in FIG. 5B should
be employed.
FIG. 22 is a block diagram showing a concrete example of the image
coding apparatus provided by the present embodiment 10. Referring
to FIG. 22, reference numeral 42 denotes an object distinguishing
unit, 43 a first frame memory group, 44 a second frame memory
group, and 138 an object identification signal.
Operation will be described subsequently.
An input image 100 includes identification signals applied to
individual objects in advance, and the identification signals are
identified by the object distinguishing unit 42. The number of each
of the thus identified objects is outputted as an object
identification signal 138 from the object distinguishing unit
42.
The motion estimating unit 15 selects, from among the first frame
memory group 43 and the second frame memory group 44, a frame
memory which corresponds to the object of the subject of coding in
accordance with the object identification signal 138, reads out a
reference image from the selected frame memory and performs motion
prediction.
Meanwhile, the motion compensation predicting unit 21 selects a
frame memory corresponding to a predetermined object in accordance
with a motion prediction mode 126 determined by the motion
estimating unit 15 and generates a predicted image 115.
On the other hand, the frame memory selecting unit 35 writes a
decoded image 108 into one of the frame memories of a predetermined
one of the frame memory groups which corresponds to a predetermined
object in accordance with the object identification signal 138.
Further, the object identification signal 138 is multiplexed
together with other coding information by the multiplexing unit 45
and sent out as a multiplexed bit stream 139 to an external
apparatus (not shown).
While, in the image coding apparatus of the present embodiment 10,
the first and second memory groups are provided to realize the
construction for switching of motion compensating prediction, for
implementation of the hardware, a plurality of frame memories can
be provided at a time by cutting a memory having a storage capacity
for the plurality of frame memories based on internal addresses. As
described above, with the image coding apparatus of the present
embodiment 10, since a prediction structure which conforms with
motion of an object can be taken, the overall prediction efficiency
is improved.
Embodiment 11
A block diagram of an image decoding apparatus which corresponds to
the image coding apparatus of the embodiment 10 shown in FIG. 22 is
shown in FIG. 23. Referring to FIG. 23, reference numeral 46
denotes a demultiplexing unit, 43 a first frame memory group, 44 a
second frame memory group, and 138 an object identification signal.
The other components are similar to those of the image decoding
apparatus of, for example, the embodiment 4 shown in FIG. 13, and
accordingly, repetitive description of them is omitted here.
Operation will be described subsequently.
In response to an object identification signal 138 demultiplexed by
the demultiplexing unit 46, the motion compensating unit 23 reads
out a reference image from one of frame memories of a predetermined
frame memory group which corresponds to a predetermined object, and
performs motion compensation corresponding to a prediction mode to
generate a predicted image 115.
In the meantime, the frame memory selecting unit 35 writes a
decoded image 108 into one of the frame memories of a predetermined
frame memory group which corresponds to a predetermined object in
accordance with the object identification signal 138. The other
processing is similar to that of the image decoding apparatus of
the embodiment 4 shown in FIG. 13, and accordingly, repetitive
description of it is omitted here.
Embodiment 12
FIG. 24 is a block diagram of an image coding apparatus which
includes a further frame memory group in addition to the
construction of the embodiment 10 described hereinabove with
reference to FIG. 22 such that it may include totaling three frame
memory groups. Referring to FIG. 24, reference numeral 49 denotes a
third frame memory group. The other components are similar to those
of the image coding apparatus of the embodiment 10 shown in FIG.
22, and accordingly, repetitive description of them is omitted
here.
Subsequently, operation will be described.
An input image 100 includes identification signals applied to
individual objects in advance, and the identification signals are
identified by the object distinguishing unit 42. The number of each
of the thus identified objects is outputted as an object
identification signal 138 from the object distinguishing unit
42.
The motion estimating unit 15 selects, from among the first frame
memory group 43, the second frame memory group 44 and the third
frame memory group 49, a frame memory which corresponds to the
object of the subject of coding in accordance with the object
identification signal 138, reads out a reference image from the
selected frame memory and performs motion prediction.
Meanwhile, the motion compensation predicting unit 21 selects a
frame memory corresponding to a predetermined object in accordance
with a motion prediction mode 126 determined by the motion
estimating unit 15 and generates a predicted image 115.
On the other hand, the frame memory selecting unit 35 writes a
decoded image 108 into one of the frame memories of a predetermined
one of the frame memory groups which corresponds to a predetermined
object in accordance with the object identification signal 138.
Further, the object identification signal 138 is multiplexed
together with other coding information by the multiplexing unit 45
and sent out as a multiplexed bit stream 139.
While, in the image coding apparatus of the present embodiment 12,
the first, second and third memory groups are provided to realize
the construction for switching of motion compensating prediction,
for implementation of the hardware, a plurality of frame memories
can be provided at a time by cutting a memory having a storage
capacity for the plurality of frame memories based on internal
addresses.
Embodiment 13
A block diagram of an image decoding apparatus corresponding to the
image coding apparatus of the embodiment 12 shown in FIG. 24 is
shown in FIG. 25. Referring to FIG. 25, reference numeral 49
denotes a third frame memory group. The other components are
similar to those of the image decoding apparatus of, for example,
the embodiment 11 shown in FIG. 23, and accordingly, repetitive
description of them is omitted here.
Operation will be described subsequently.
In response to an object identification signal 138 demultiplexed by
the demultiplexing unit 46, the motion compensating unit 23 reads
out a reference image from one of frame memories of a predetermined
frame memory group which corresponds to a predetermined object, and
performs motion compensation corresponding to a prediction mode to
generate a predicted image 115.
In the meantime, the frame memory selecting unit 35 writes a
decoded image 108 into one of the frame memories of a predetermined
frame memory group which corresponds to a predetermined object in
accordance with the object identification signal 138.
The other processing is similar to that of the image decoding
apparatus of the embodiment 11 shown in FIG. 23, and accordingly,
repetitive description of it is omitted here.
Embodiment 14
The image coding apparatus such as embodiment 12 shown in FIG. 24
may be modified such that re-writing of image contents of a region,
in which an object of a subject of coding is included, of a frame
memory corresponding to the object in the second frame memory in
which a decoded image of the object in the past is stored is
performed after each certain interval of time or in response to a
control signal from the outside.
FIG. 26 is a diagrammatic view illustrating that, for example, with
a decoded image of all macroblocks including a region occupied by a
certain object, image contents in a macroblock or macroblocks at
the same position of a frame memory in the second frame memory
group which corresponds to the object are re-written. Accordingly,
in the case of FIG. 26, contents of totaling four macroblocks in
two vertical columns and two horizontal rows are updated.
Further, where re-writing of image contents of a region, in which
an object of a subject of coding is included, of a frame memory
corresponding to the object in the third frame memory in which a
decoded image of the object in the past is stored is performed
after each certain interval of time or in response to a control
signal from the outside, the writing operation into a frame memory
in the second frame memory group in the foregoing description
should be applied to the writing operation into a frame memory in
the third frame memory group.
Also with a decoding apparatus which corresponds to the image
coding apparatus such as embodiment 12 shown in FIG. 24 as
described above, re-writing of image contents of a region, in which
an object is included, of a frame memory corresponding to the
object in the second frame memory group in which a decoded image of
the object in the past is stored can be controllably performed
after a certain interval of time or in response to a control signal
from the outside.
Embodiment 15
The image coding apparatus of the embodiment 10 shown in FIG. 22
can be modified such that searching ranges of motion vector
searching for a reference image from a frame memory of the first
frame memory group which corresponds to an object and another
reference image from another frame memory of the second frame
memory group which corresponds to another object are varied for the
individual objects.
For example, in the image coding apparatus of the embodiment 10
shown in FIG. 22, if a background which exhibits a comparatively
small amount of motion as an object is stored in advance in a frame
memory of the second frame memory group which corresponds to the
object whereas an operation of successively writing a decoded image
of another object which exhibits a comparatively large amount of
motion at any time into another frame memory of the first frame
memory group which corresponds to the object is performed, then a
high prediction efficiency can be maintained for both of the
objects.
Further, the image coding apparatus of the embodiment 12 shown in
FIG. 24 may be modified such that searching ranges of motion vector
searching for a reference image from s from memory of the first
frame memory group which corresponds to an object, another
reference image from another frame memory of the second frame
memory group which corresponds to another object and a further
reference image from a further frame memory of the third frame
memory group which corresponds to a further object are varied for
the individual objects.
For example, in the image coding apparatus of the embodiment 12
shown in FIG. 24, if a background which exhibits a comparatively
small amount of motion as an object is stored in advance in a frame
memory of the third frame memory group which corresponds to the
object whereas an operation of successively writing a decoded image
of another object which exhibits a comparatively large amount of
motion at any time into another frame memory of the first frame
memory group or the second frame memory group which corresponds to
the object is performed, then a high prediction efficiency can be
maintained for all of the three objects.
As described above, since searching ranges for a motion vector are
set separately from each other for a plurality of frame memory
groups referred to by objects. for example, for an object which
exhibits a comparatively small amount of motion, the information
generation amount of motion vectors can be reduced by making the
searching range for a motion vector narrow.
Embodiment 16
FIG. 27 is a block diagram showing an image coding apparatus
according to an embodiment 16 of the present invention. Referring
to FIG. 27, reference 47 denotes a differential vector generating
unit. The differential vector generating unit 47 holds motion
vectors in the past obtained by referring to images of individual
objects from frame memories of the first frame memory group which
correspond to the objects and motion vectors in the past obtained
by referring to images of the individual objects from frame
memories of the second frame memory group which correspond to the
objects in the image coding apparatus of the embodiment 10 shown in
FIG. 22 separately for certain periods of time and calculates
difference vectors separately for the individual objects. The other
construction is similar to that of the image coding apparatus of
the embodiment 10 shown in FIG. 22, and accordingly, repetitive
description of it is omitted here.
Subsequently, operation will be described.
The motion estimating unit 15 performs motion estimation of a
current image 101 of an object of a subject of coding using an
image in a frame memory corresponding to the object in one of the
first frame memory group and the second frame memory group selected
by motion estimation as a reference image to detect a motion vector
123.
Based on the motion vector 123, the differential vector generating
unit 47 selects a candidate vector (MV1, MV2 or MV3 mentioned
hereinabove) from among motion vectors of the object in the past
stored in the differential vector generating unit 47 and outputs a
difference vector 141 of the candidate vector from the motion
vector 123. The difference vector 141 is coded into a variable
length codeword by the variable length coding unit 17. Accordingly,
the differential vector generating unit 47 has a memory function of
holding motion vectors in the past separately for certain periods
of time for the individual frame memory groups.
Embodiment 17
A block diagram of a decoding apparatus corresponding to the image
coding apparatus of the embodiment 16 shown in FIG. 27 is shown in
FIG. 28. Referring to FIG. 28, reference numeral 48 denotes a
motion vector adding unit which selects a candidate vector from
among motion vectors of an object in the past stored in advance
therein and adds the selected candidate vector to a difference
vector 141 variable length decoded by the variable length decoding
unit 22. The other construction is similar to that of the image
decoding apparatus of the embodiment 11 shown in FIG. 22, and
accordingly, repetitive description of it is omitted here.
Subsequently, operation will be described.
In the image decoding apparatus of the present embodiment 17, a
difference vector 141 variable length coded by the variable length
decoding unit 22 is supplied to the motion vector adding unit 48,
by which a candidate vector is selected from among motion vectors
of an object in the past stored therein and added to the difference
vector 141 to regenerate a motion vector 123.
The motion vector 123 is sent to the motion compensating unit 23.
The motion compensating unit 23 receives the motion vector 123,
reads out an image in the memory group 43 or 44 corresponding to
the object in the frame memory group selected by the frame memory
selecting unit 35 as a reference image, and outputs a predicted
image 115. The other processing is similar to the operation of the
image decoding apparatus of the embodiment 11 shown in FIG. 23, and
accordingly, repetitive description of it is omitted here.
Embodiment 18
A construction of an image coding apparatus which includes a third
frame memory group 49 in addition to the construction of the image
coding apparatus of the embodiment 16 shown in FIG. 27 is shown in
FIG. 29. The other construction is similar to that of the image
coding apparatus of the embodiment 16 shown in FIG. 27, and
accordingly, repetitive description of it is omitted here.
Subsequently, operation will be described.
The motion estimating unit 15 performs motion estimation of a
current image 101 of an object of a subject of coding using an
image in a frame memory corresponding to the object in one of the
first frame memory group, the second frame memory group and the
third frame memory group selected by motion estimation as a
reference image to detect a motion vector 123.
Based on the motion vector 123, the differential vector generating
unit 47 selects a candidate vector (MV1, MV2 or MV3 mentioned
hereinabove) from among motion vectors of the object in the past
stored in the differential vector generating unit 47 and outputs a
difference vector 141 of the candidate vector from the motion
vector 123. The difference vector 141 is coded into a variable
length codeword by the variable length coding unit 17.
Also in this instance, the differential vector generating unit 47
has a memory function of holding motion vectors in the past
separately for certain periods of time for the individual frame
memory groups. Since the other processing is similar to the
operation of the image coding apparatus of the embodiment 16 shown
in FIG. 27, repetitive description of it is omitted herein.
Embodiment 19
A construction of an image decoding apparatus corresponding to the
image coding apparatus of the embodiment 18 shown in FIG. 29 is
shown in FIG. 30. Referring to FIG. 30, reference numeral 49
denotes a third frame memory group. Since the other construction is
similar to that of the image decoding apparatus of the embodiment
17 shown in FIG. 28, repetitive description of it is omitted
here.
Subsequently, operation will be described.
A difference vector 141 variable length coded by the variable
length decoding unit 22 is supplied to the motion vector adding
unit 48, by which a candidate vector is selected from among motion
vectors of an object in the past stored therein and added to the
difference vector 141 to regenerate a motion vector 123. The motion
vector 123 is sent to the motion compensating unit 23. The motion
compensating unit 23 reads out a reference image in a frame memory
corresponding to the object in the selected frame memory group, and
outputs a predicted image 115.
As described above, if a differential vector generating unit which
has a memory function of holding a number of motion vectors, which
is equal to the number of the frame memory groups, in the past
separately for certain periods of time for the individual frame
memory groups and calculates a difference vector between a detected
motion vector and a candidate vector is provided, then the
information generation amount of motion vectors can be
suppressed.
As described above, with the image coding apparatus of the present
invention, since a background image is stored and motion
compensating prediction is performed using background prediction
based on the stored background image, there is an effect that
coding can be performed while keeping a high prediction efficiency
without being influenced by a coding sequence.
Further, with the image coding apparatus and the image decoding
apparatus of the present invention, since re-writing of image
contents in the individual frame memories is performed in units of
a picture after a certain interval of time or in response to a
control signal from the outside, there is another effect that the
image contents of the frame memories can always be kept to contents
with which a high prediction efficiency in background prediction
can be obtained.
Further, with the image coding apparatus and the image decoding
apparatus of the present invention, since re-writing of the image
contents of the individual frame memories is performed in units of
a macroblock after a certain interval of time or in response to a
control signal from the outside, there is a further effect that the
image contents of the frame memories can always be kept to contents
with which a high prediction efficiency in background prediction
can be obtained with a finer level.
Further, with the image coding apparatus and the image decoding
apparatus of the present invention, since the searching ranges for
a motion vector to be used for motion estimation are variably set
for the plurality of frame memories provided in the coding
apparatus, for example, when motion is to be searched for from
reference to a frame memory in which a screen which involves a
comparatively small amount of motion is written, a comparatively
short code can be given, and accordingly, there is a still further
effect that the coding information amount of motion vectors can be
reduced.
Further, with the image coding apparatus and the image decoding
apparatus of the present invention, since the differential vector
generating unit which has a memory function of holding a number of
motion vectors, which is equal to the number of the frame memories,
in the past separately for a certain period of time and calculates
a difference vector between a detected motion vector and a
candidate vector is provided, there is a yet further effect that
the information generation amount of motion vectors can be
suppressed.
Further, with the image coding apparatus and the image decoding
apparatus of the present invention, since motion compensating
prediction is performed using the plurality of frame memories for
the individual objects which construct a screen, a prediction
structure conforming to motion of the objects can be taken, and
consequently, there is a yet further effect that the overall
prediction efficiency is improved.
Further, with the image coding apparatus and the image decoding
apparatus of the present invention, since only regions of the frame
memories in the frame memory groups in which an object of a subject
of coding is included are re-written after a certain interval of
time or in response to an external control signal, there is a yet
further effect that a high efficiency in background prediction can
be maintained.
Further, with the image coding apparatus and the image decoding
apparatus of the present invention, since the searching ranges for
a motion vector are set separately for the plurality of frame
memory groups referred to by an object, there is a yet further
effect that, for example, for an object which exhibits a
comparatively small amount of motion, the information generation
amount of motion vectors can be reduced by making the searching
range for a motion vector narrow.
Furthermore, with the image coding apparatus and the image decoding
apparatus of the present invention, since the differential vector
generating unit which has a memory function of holding a number of
motion vectors, which is equal to the number of the frame memory
groups, in the past separately for certain periods of time for the
individual frame memory groups and calculates a difference vector
between a detected motion vector and a candidate vector is
provided, there is an additional effect that the information
generation amount of motion vectors can be suppressed.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *