U.S. patent application number 10/885805 was filed with the patent office on 2005-02-03 for video coding device and video decoding device.
This patent application is currently assigned to Sharp Kabushiki. Invention is credited to Aono, Tomoko, Katata, Hiroyuki, Kusao, Hiroshi, Saiga, Hisashi.
Application Number | 20050025239 10/885805 |
Document ID | / |
Family ID | 26463014 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050025239 |
Kind Code |
A1 |
Aono, Tomoko ; et
al. |
February 3, 2005 |
Video coding device and video decoding device
Abstract
A video coding device capable of adaptively processing input
video data according to property of the data and realizing
effective progressive transmission of the coded data even if image
components are different in size and/or different in the number of
subbands. The above-mentioned object can be realized by the
provision of a transferring-order deciding and ranging portion that
can prepare an integrated component unit by forming combinations of
subband-based frequency-coefficients of respective components Y, U
and V and can change the number of respective elements of
respective components Y, U and V.
Inventors: |
Aono, Tomoko; (Chiba-shi,
JP) ; Saiga, Hisashi; (Tenri-shi, JP) ;
Katata, Hiroyuki; (Chiba-shi, JP) ; Kusao,
Hiroshi; (Chiba-shi, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Sharp Kabushiki
Osaka-shi
JP
|
Family ID: |
26463014 |
Appl. No.: |
10/885805 |
Filed: |
July 8, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10885805 |
Jul 8, 2004 |
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09875098 |
Jun 7, 2001 |
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6813314 |
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09875098 |
Jun 7, 2001 |
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09381029 |
Sep 15, 1999 |
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6259735 |
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09381029 |
Sep 15, 1999 |
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PCT/JP98/02349 |
May 28, 1998 |
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Current U.S.
Class: |
375/240.11 ;
375/240.18; 375/240.25; 375/E7.047; 375/E7.057; 375/E7.07;
375/E7.166 |
Current CPC
Class: |
H04N 19/13 20141101;
H04N 19/61 20141101; H04N 19/64 20141101; H04N 19/36 20141101; H04N
19/129 20141101; H04N 19/186 20141101; H04N 19/63 20141101; H04N
11/042 20130101 |
Class at
Publication: |
375/240.11 ;
375/240.18; 375/240.25 |
International
Class: |
H04N 007/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 1997 |
JP |
9-139591 |
May 11, 1998 |
JP |
10-126938 |
Claims
1-12. (Canceled).
13. A video coding device comprising: a subband-decomposing means
for decomposing into subbands each of a plurality of components
composing an image; a coefficient coding means for encoding
frequency coefficients in the subbands to generate coded
coefficient data for each subband; and a variable-length coding
means for performing variable-length coding of the coded
coefficient data, wherein the number of subbands of at least one
component is different from the number of subbands of other
components.
14. A video coding device comprising: a subband-decomposing means
for decomposing into subbands each of a plurality of components
composing an image; a coefficient coding means for encoding
frequency coefficients in the subbands to generate coded
coefficient data for each subband; and a variable-length coding
means for performing variable-length coding of the coded
coefficient data, wherein an image size and the number of subbands
of at least one component are different from an image size and the
number of subbands of other components.
15. A video coding device as defined in any of claims 13 and 14,
wherein the sets of coded coefficient data of the subbands for each
of the components are transferred in an ascending order of
frequencies starting from a low frequency subband.
16. A video decoding device comprising: a variable-length decoding
means for performing variable-length decoding of coded data of an
image composed of a plurality of components to obtain coded
coefficient data; a coefficient decoding means for decoding the
coded coefficient data to obtain frequency coefficients; and a
subband synthesizing means for reconstructing a decoded image by
synthesizing subbands of the frequency coefficients for respective
components, wherein the number of subbands of at least one
component is different from the number of subbands of other
components.
17. A video decoding device comprising: a variable-length decoding
means for performing variable-length decoding of coded data of an
image composed of a plurality of components to obtain coded
coefficient data; a coefficient decoding means for decoding the
coded coefficient data to obtain frequency coefficients; and a
subband synthesizing means for reconstructing a decoded image by
synthesizing subbands of the frequency coefficients for respective
components, wherein an image size and the number of subbands of at
least one component are different from an image size and the number
of subbands for other components.
18. A video decoding device as defined in any of claims 16 and 17,
wherein the sets of coded coefficient data of the subbands for each
of the components are received in an ascending order of frequencies
starting from a low frequency subband.
19. An image decoding device comprising: a variable-length decoder
for decoding variable-length coded data of a hierarchically coded
image, said hierarchically coded image including more than one kind
of luminance or chrominance components; a decoding truncator for
giving a decoding-stop command at any position designated by a
user; a coefficient decoder for decoding the variable-length coded
data; and a subband synthesizer for reconstructing a decoded image
by synthesizing subbands containing data decoded by the coefficient
decoder for said components, wherein an image decoded with
truncated data is displayable by using data decoded before
terminating decoding of said image.
20. An image decoding device comprising: a variable-length decoder
for decoding variable-length coded data of a hierarchically coded
image, said hierarchically coded image including more than one kind
of luminance or chrominance components; a decoding truncator for
giving a decoding-stop command at any position designated by a
user; a coefficient decoder for decoding the variable-length coded
data; and a subband synthesizer for reconstructing a decoded image
by synthesizing subbands containing data decoded by the coefficient
decoder for said components, wherein an image decoded with
truncated data is displayable by using data decoded before
terminating decoding of said image when at least one kind of said
components is different in size and in number of subbands from
other kinds of said components.
Description
TECHNICAL FIELD
[0001] The present invention pertains to the field of digital video
processing and relates to a video coding device for efficiently
encoding video data and a video decoding device for decoding video
data coded by the video coding device.
BACKGROUND ART
[0002] Recently, there has been proposed a subband coding method
that can efficiently encode and decode video signals. The
well-known high-efficient subband encoding method is used to
decompose an input image into frequency bands by a bank of
band-decomposing filters. The band-decomposing filter-bank is a
one-dimensional filter-bank that can serve as a two-dimensional
band-decomposing filter-bank by repeating processing the input
image in horizontal and vertical directions. This method was
reported by Fujii, Noumura. "Topics on Wavelet Transform" in a
Report of "TECHNICAL REPORT of IEICE, IE92-11, 1992".
[0003] In the prior art, a subband image as shown in FIG. 1B
obtained by conducting two-dimensional subband decomposition three
times. The first two-dimensional subband decomposition obtains a
horizontal high-pass and a vertical low-pass band, a horizontal
low-pass and vertical high-pass band and a horizontal and vertical
high-pass band, which are designated by HL1, LH1 and HH1
respectively. A horizontal and vertical low-pass band obtained by
the first decomposition is further subjected to two-dimensional
band-decomposition by which three subbands HL2, LH2 and HH2 are
obtained.
[0004] A horizontal and vertical low-pass subband obtained by the
second decomposition is further subjected to third two-dimensional
subband decomposition by which three subbands HL3, LH3 and HH3 and
a horizontal and vertical low-pass subband LL3 are obtained. A
Wavelet-converting filter-bank or a band-decomposing and
synthesizing filter-bank may be used as the band-decomposing
filter-bank. Thus, the decomposed subband-images are of a
hierarchical (layer) structure from low-frequency band to
high-frequency band.
[0005] Progressive image transmitting can be easily realized
utilizing the hierarchical structure of the subband images. The
progressive image transmitting method enables a video decoding
device to reproduce a low-resolution image by using only a part of
coded data. The more coded data is reproduced, the higher
resolution the decoded image has. Japanese Laid-Open Patent
Publication (TOKKAI HEI) No. 8-242379 describes a system (referred
hereinafter to as a prior art system) to realize the progressive
image transmitting.
[0006] A video coding device using in the prior art system
comprises a subband decomposing portion for decomposing an input
image into subband images by using two-dimensional decomposing
filters, a coefficient coding portion for encoding coefficients of
the decomposed subband images, a variable-length coding portion for
performing variable-length coding of the coded coefficient data
from the coefficient coding portion and a line-transmitting portion
for transmitting a plurality of components composing the image per
line at a time. The coefficient coding portion performs encoding
the coefficients by using any one of various kinds of coding
methods (e.g., DPCM coding, zero-tree coding, and scalar-quantizing
coding). This process includes a quantizing step.
[0007] The operation of the line transmitting portion will be
described below in detail, by way of example, with an input image
composed of three-components Y (a luminance component) and U, V
(chrominance components) and being conducted subband decomposition
three times as shown in FIG. 1B. Processing starts from a subband
LL3, which gives the lowest resolution of the image.
[0008] In the example, the line-transmitting portion transmits the
components Y, U and V sequentially line by line in the order from
the first line of the subband LL3. Having transferred all lines of
the subband LL3, the portion transfers the components Y, U and V in
the subbands LH3, HL3 and HH3 respectively in the order: the
component Y on the first lines of the subbands LH3, HL3 and HH3;
the component U on the first lines of the subbands LH3, HL3 and
HH3; the component V on the first lines of the subbands LH3, HL3
and HH3; the component Y on the second lines of the subbands LH3,
HL3 and HH3; U on the second lines of LH3, HL3 and HH3; V on the
second lines of the subbands LH3, HL3 and HH3 and so on. Having
transmitted all lines of LH3, HL3 and HH3, the line transmitting
portion transfers, in similar way, lines of LH2, HL2; HH2 and,
then, lines of LH1, HL1, HH1. The above-mentioned procedure of the
line-transmitting portion is executed according to a programed
flow.
[0009] Orderly transmission of the components Y, U, V composing the
image per line produces coded data having a hierarchical
structure.
[0010] The prior art video decoding device comprises a line
receiving portion for receiving the coded data from the
line-transmitting portion of the video-coding device
above-mentioned and rearranging the data to respective component
groups, a variable-length decoding portion for decoding the
rearranged variable-length-coded data, a decoded data counting
portion for counting bits of data decoded by the variable-length
decoding portion, a decoding truncating portion for comparing the
number of the bits counted by the decoded-data counting portion
with a preset threshold or an externally-given threshold to give a
command for stopping the decoding operation of the variable-length
decoding portion when the number of decoded bits exceeds the
threshold, a data completing portion for compensating for lack of
truncated data by adding zero when having truncated the decoding
the coded data at the specified number of bits, a coefficient
decoding portion for decoding coded coefficient data by reversing
the same processing procedure of the coefficient coding portion and
a subband synthesizing portion for synthesizing an image from the
subbands through two-dimensional synthesizing filters.
[0011] The video decoding device can thus reproduce an entire image
from coded data having a hierarchical structure or a part
thereof.
[0012] The conventional video-coding and video-decoding system can
realize progressive image transmitting by transmitting image
components per line in an ascending order starting from the
lowest-resolution band-image. However, the prior art system
encounters several inconvenient problems resulting from the fixed
transfer-unit of a line. For example, an image composed of
luminance component Y and chrominance components U and V may be
easier recognized by transmitting only the component Y before the
components U and V rather than transmitting all components as a
unit.
[0013] In this case, it is preferable to transfer the image
components subband by subband, not by line. Furthermore, it is
proved that an image composed of components R, G, B may be
reproduced with better subjective image-quality at the decoding
terminal when coded coefficients of the respective components R, G
and B are transmitted one by one. This is because these components
have substantially the same influence on the visual property.
[0014] The prior art system presumes that components of an image
have the same size. Therefore, it cannot be adaptable to an input
image composed of different sizes of components in format of, e.g.,
4:2:2 or 4:2:0.
[0015] Furthermore, the prior art system presumes that respective
components of an image have the same number of subbands and cannot
be adaptable to an input image whose components are divided into
different numbers of subbands.
DISCLOSURE OF INVENTION
[0016] The present invention is directed to a system for effective
progressive image transmitting by solving the foregoing problems
involved in the prior arts.
[0017] (1) Accordingly, an object of the present invention is to
provide a video coding device, which is provided with a
subband-decomposing means for decomposing an image being composed
of N (N.gtoreq.2) kinds of luminance or chrominance components into
subband images for each of components A.sup.n (1.ltoreq.n.ltoreq.N,
where n is an integer) composing an image to be coded, coefficient
coding means for encoding a frequency coefficient of the subband
images, rearranging means for preparing integrated component units
by combining frequency coefficients included in respective
components A.sup.n according to the coded coefficient data prepared
by the coefficient coding means and rearranging the prepared
integrated component units of the coefficient-coded data in an
ascending order of subband image resolution, starting from the
integrated component unit including the coded coefficient data of
the lowest resolution subband, and a variable-length coding means
for performing variable-length encoding of the rearranged
coefficient-coded data, wherein the rearranging means prepares each
of the integrated component units by setting therein the frequency
coefficients contained in the respective components A.sup.n, which
are all frequency-coefficients included in m (m.gtoreq.1) pieces of
the respective components' subbands, when the components A.sup.n
are have the same size and the same number of subbands.
[0018] (2) Correspondingly, another object of the present invention
is to provide a video decoding device, which is provided with a
variable-length decoding means for decoding variable-length coded
data, a decoded-data counting means for counting bits of each
integrated component unit decoded by the variable-length decoding
means, a decoding truncating means for comparing the number of bits
counted by the decoded-data counting means with an externally-given
number of bits and giving a decoding-stop command when the number
of decoded bits exceeds the given number of bits, a component
separating means for separating the decoded integrated component
unit into respective components A.sup.n, a data completing means
for compensating for lack of truncated data by adding a specified
value to each of the components composing a screenful image, data
arranging means for arranging coded coefficient data separated by
the component separating means into specified positions for
respective components A.sup.n, a coefficient decoding means for
decoding coded-coefficient data separated and arranged for
respective components A.sup.n by the component separating means,
and a subband synthesizing means for reproducing a decoded image by
combining subbands of data decoded by the coefficient decoding
means for respective components A.sup.n, wherein the component
separating means separates the integrated component unit as
combinations of all frequency coefficients contained in m
(m.gtoreq.1) subbands for respective components A.sup.n when the
respective components A.sup.n have the same size and the same
number of subbands.
[0019] The integrated component units contains all frequency
coefficients in m (m.gtoreq.1) respective subbands of respective
component A.sup.n. Therefore, specified subbands of the image
components such as luminance signal Y and chrominance signals U and
V that may have different levels of influence on human visual
property can be transmitted first to enable one to recognize a
summary of the image at an earlier stage of decoding at the
decoding side. When a codable image is known to be of higher
resolution in a specified direction, the coding device can transmit
first coded coefficients of higher-resolution-direction subbands
and the decoding device can decode those coded coefficients,
terminate the decoding in the midway of decoding all coded data and
reproduce the image from only data decoded till that time to
improve subjective-image quality of the image.
[0020] (3) Another object of the present invention is to provide a
video coding device, which is provided with a subband-decomposing
means for decomposing an image being composed of N (N.gtoreq.2)
kinds of luminance or chrominance components into subband images
for each of components A.sup.n (1.ltoreq.n.ltoreq.N, where n is an
integer) composing an image to be coded, coefficient coding means
for encoding a frequency coefficient of the subband images,
rearranging means for preparing integrated component units by
combining frequency coefficients included in respective components
A.sup.n according to the coded coefficient data prepared by the
coefficient coding means and rearranging the prepared integrated
component units of the coefficient-coded data in an ascending order
of subband image resolution, starting from the integrated component
unit including the coded coefficient data of the lowest resolution
subband, and a variable-length coding means for performing
variable-length encoding of the rearranged coefficient-coded data,
wherein the rearranging means prepares each of the integrated
component units by setting therein the frequency coefficients
included in the respective components A.sup.n as m (m.gtoreq.1)
pieces of frequency-coefficients contained at the same relative
positions in m (m.gtoreq.1) pieces of the respective components'
subbands when the components A.sup.n have the same size and the
same number of subbands.
[0021] (4) Correspondingly, another object of the present invention
is to provide a video decoding device, which is provided with a
variable-length decoding means for decoding variable-length coded
data, a decoded-data counting means for counting bits of each
integrated component unit decoded by the variable-length decoding
means, a decoding truncating means for comparing the number of bits
counted by the decoded-data counting means with an externally-given
number of bits and giving a decoding-stop command when the number
of decoded bits exceeds the given number of bits, a component
separating means for separating the decoded integrated component
unit into respective components A.sup.n, a data completing means
for compensating for lack of truncated data by adding a specified
value to each of the components composing a screenful image, data
arranging means for arranging coded coefficient data separated by
the component separating means into specified positions for
respective components A.sup.n, a coefficient decoding means for
decoding coded-coefficient data separated and arranged for
respective components A.sup.n by the component separating means,
and a subband synthesizing means for reproducing a decoded image by
combining subbands of data decoded by the coefficient decoding
means for respective components A.sup.n, wherein the component
separating means separates the integrated component unit into
combinations of m (m.gtoreq.1) pieces of frequency coefficients
having the same relative positions in respective m (m.gtoreq.1)
subbands of the respective components A.sup.n when the components
A.sup.n have the same size and the same number of subbands.
[0022] Therefore, the devices operate with integrated component
units whose elements are m (m.gtoreq.1) pieces of frequency
coefficients having the same relative positions in m (m.gtoreq.1)
respective subbands of respective components A.sup.n and can decode
those coded coefficients, terminate the decoding in the midway of
decoding all the coded data and reproduce the image from only the
data decoded till that time to improve subjective-image quality of
the image when the image is composed of components. R, G and B that
have substantially almost the same influence on human visual
property.
[0023] (5) Another object of the present invention is to provide a
video coding device, which is provided with a subband-decomposing
means for decomposing an image being composed of N (N.gtoreq.2)
kinds of luminance or chrominance components into subband images
for each of components A.sup.n (1.ltoreq.n.ltoreq.N, where n is an
integer) composing an image to be coded, coefficient coding means
for encoding a frequency coefficient of the subband images,
rearranging means for preparing integrated component units by
combining frequency coefficients included in respective components
A.sup.n according to the coded coefficient data prepared by the
coefficient coding means and rearranging the prepared integrated
component units of the coefficient-coded data in an ascending order
of subband image resolution, starting from the integrated component
unit including the coded coefficient data of the lowest resolution
subband, and a variable-length coding means for performing
variable-length encoding of the rearranged coefficient-coded data,
wherein the rearranging means prepares each of the integrated
component units by setting therein the different number of
frequency-coefficients in the respective components A.sup.n
according to each component size when the components A.sup.n are
different in size and have the same number of subbands.
[0024] (6) Correspondingly, another object of the present invention
is to provide a video decoding device, which is provided with a
variable-length decoding means for decoding variable-length coded
data, a decoded-data counting means for counting bits of each
integrated component unit decoded by the variable-length decoding
means, a decoding truncating means for comparing the number of bits
counted by the decoded-data counting means with an externally-given
number of bits and giving a decoding-stop command when the number
of decoded bits exceeds the given number of bits, a component
separating means for separating the decoded integrated component
unit into respective components A.sup.n, a data completing means
for compensating for lack of truncated data by adding a specified
value to each of the components composing a screenful image, data
arranging means for arranging coded coefficient data separated by
the component separating means into specified positions for
respective components A.sup.n, a coefficient decoding means for
decoding coded-coefficient data separated and arranged for
respective components A.sup.n by the component separating means,
and a subband synthesizing means for reproducing a decoded image by
combining subbands of data decoded by the coefficient decoding
means for respective components A.sup.n, wherein the component
separating means separates the integrated component unit as
combinations of different pieces of frequency coefficients
according to respective component sizes when the respective
components A.sup.n are different in size and have the same number
of subbands.
[0025] The devices can be adapted to process an image whose
luminance and chrominance components are different from each other
by resolution, having the great advantage over the conventional
method that can be applied to an image whose components have the
same resolution. This feature provided by the present invention is
desirable in particular to digital image processing since many
digital images are usually formatted to have higher resolution of
the luminance component than that of chrominance component.
[0026] (7) Another object of the present invention is to provide a
video coding device, which is provided with a subband-decomposing
means for decomposing an image being composed of N (N.gtoreq.2)
kinds of luminance or chrominance components into subband images
for each of components A.sup.n (1.ltoreq.n.ltoreq.N, where n is an
integer) composing an image to be coded, coefficient coding means
for encoding a frequency coefficient of the subband images,
rearranging means for preparing integrated component units by
combining the subbands included in respective components A.sup.n
according to the coded coefficient data prepared by the coefficient
coding means and rearranging the prepared integrated component
units of the coefficient-coded data in an ascending order of
subband image resolution, starting from the integrated component
unit including the coded coefficient data of the lowest resolution
subband, and a variable-length coding means for performing
variable-length encoding of the rearranged coefficient-coded data,
wherein the rearranging means prepares each of the integrated
component units by combining the same number of low-resolution
subbands and the different number of high-resolution subbands of
the respective components A.sup.n when the components A.sup.n are
different in size and different in the number of subbands.
[0027] (8) Correspondingly, another object of the present invention
is to provide a video decoding device, which is provided with a
variable-length decoding means for decoding variable-length coded
data, a decoded-data counting means for counting bits of each
integrated component unit decoded by the variable-length decoding
means, a decoding truncating means for comparing the number of bits
counted by the decoded-data counting means with an externally-given
number of bits and giving a decoding-stop command when the number
of decoded bits exceeds the given number of bits, a component
separating means for separating the decoded integrated component
unit into respective components A.sup.n, a data completing means
for compensating for lack of truncated data by adding a specified
value to each of the components composing a screenful image, data
arranging means for arranging coded coefficient data separated by
the component separating means into specified positions for
respective components A.sup.n, a coefficient decoding means for
decoding coded-coefficient data separated and arranged for
respective components A.sup.n by the component separating means,
and a subband synthesizing means for reproducing a decoded image by
combining subbands of data decoded by the coefficient decoding
means for respective components A.sup.n, wherein the component
separating means separates the integrated component unit as
combinations of the same number of low-resolution subbands and the
different number of high-resolution subbands of respective
components A.sup.n when the respective components A.sup.n are
different in size and different in the number of subbands.
[0028] The devices can be adapted to process an image whose
luminance and chrominance components are different from each other
by resolution and have different subband-decomposition levels,
getting a great advantage over the conventional method that can be
applied to an image whose components have the same resolution and
the same number of subbands. This feature provided by the present
invention is desirable in particular to digital image processing
since many digital images are usually formatted to have higher
resolution of the luminance component than that of the chrominance
component and it is general to vary the subband-decomposition level
according to the resolution of the component.
[0029] (9) Another object of the present invention is to provide a
video coding device, which is provided with a subband-decomposing
means for decomposing an image being composed of N (N.gtoreq.2)
kinds of luminance or chrominance components into subband images
for each of components A.sup.n (1.ltoreq.n.ltoreq.N, where n is an
integer) composing an image to be coded, coefficient coding means
for encoding a frequency coefficient of the subband images,
rearranging means for preparing integrated component units by
combining the subbands included in respective components A.sup.n
according to the coded coefficient data prepared by the coefficient
coding means and rearranging the prepared integrated component
units of the coefficient-coded data in an ascending order of
subband image resolution, starting from the integrated component
unit including the coded coefficient data of the lowest resolution
subband, and a variable-length coding means for performing
variable-length encoding of the rearranged coefficient-coded data,
wherein the rearranging means prepares each of the integrated
component units by combining the same number of high-frequency
subbands and the different number of low-frequency subbands of the
respective components A.sup.n when the components A.sup.n are
different in size and different in the number of subbands.
[0030] (10) Correspondingly, another object of the present
invention is to provide a video decoding device, which is provided
with a variable-length decoding means for decoding variable-length
coded data, a decoded-data counting means for counting bits of each
integrated component unit decoded by the variable-length decoding
means, a decoding truncating means for comparing the number of bits
counted by the decoded-data counting means with an externally-given
number of bits and giving a decoding-stop command when the number
of decoded bits exceeds the given number of bits, a component
separating means for separating the decoded integrated component
unit into respective components A.sup.n, a data completing means
for compensating for lack of truncated data by adding a specified
value to each of the components composing a screenful image, data
arranging means for arranging coded coefficient data separated by
the component separating means into specified positions for
respective components A.sup.n, a coefficient decoding means for
decoding coded-coefficient data separated and arranged for
respective components A.sup.n by the component separating means,
and a subband synthesizing means for reproducing a decoded image by
combining subbands of data decoded by the coefficient decoding
means for respective components A.sup.n, wherein the component
separating means separates the integrated component unit as
combinations of the same number of high-resolution subbands and the
different number of low-resolution subbands of respective
components A.sup.n when the components A.sup.n are different sizes
and different in the number of subbands.
[0031] The devices can be adapted to process an image whose
luminance and chrominance components have different resolution
levels and different subband-decomposition levels, getting a great
advantage over the conventional method that can be applied to an
image whose components have the same resolution and the same number
of subbands. Furthermore, these aspects of the present invention
provide such a feature that each integrated component unit always
reflects the ratio of numbers of respective components contained in
an input image. This feature eliminates the need for decoding
redundant data at the decoding side when decoding the amount of
data according to the resolution of the display unit.
[0032] (11) Another object of the present invention is to provide a
video coding device, which is based on the device of (9)
above-mentioned and further characterized in that the rearranging
means prepares each of the integrated component units by combining
lowest ones of resolution subbands of the respective components
A.sup.n and different numbers of all other low-resolution-level
subbands of the respective components A.sup.n when the respective
components A.sup.n are different in size and different in the
number of subbands.
[0033] (12) Correspondingly, the present invention also provides a
video-decoding device, which is based on the device of (10)
above-mentioned and further characterized in that the component
separating means separates the integrated component unit into
combinations of subbands for respective components, each
combination composed of one lowest resolution subband and the
different numbers of all other low-resolution subbands.
[0034] The devices can first separate and transmit
lowest-resolution subbands of respective components A.sup.n to
first give a summary content of an image, making it possible to
improve subjective quality of the reproduced image.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1A is a view for explaining a subband coding
method.
[0036] FIG. 1B is a view for explaining a subband coding
method.
[0037] FIG. 2 is a view for explaining a progressive video
transmission system.
[0038] FIG. 3 is a block-diagram of a prior art video coding
device.
[0039] FIG. 4 is a block-diagram of a prior art video decoding
device.
[0040] FIG. 5 depicts a sequence of transferring subband image
coefficients according to the prior art video coding device.
[0041] FIG. 6 is a flow chart for explaining the operation of a
prior art video coding device.
[0042] FIG. 7 is a block-diagram of a video coding device which is
a first embodiment of the present invention.
[0043] FIG. 8 is a block-diagram of a video decoding device which
is a first embodiment of the present invention.
[0044] FIG. 9 depicts an example of decomposing image components
into subbands in the first embodiment of the present invention.
[0045] FIG. 10 depicts an example of a sequence of transferring
coefficients of subband images in the first embodiment of the
present invention.
[0046] FIG. 11 depicts another example of a sequence of
transferring coefficients of subband images in the first embodiment
of the present invention.
[0047] FIG. 12 depicts an exemplified sequence of scanning
coefficients in respective subbands in the first embodiment of the
present invention.
[0048] FIG. 13 depicts an example of collecting a plurality of
subbands into elements of an integrated component unit in the first
embodiment of the present invention.
[0049] FIG. 14 depicts an example of using coefficients of each
line in each subband as an element of an integrated component unit
in the first embodiment of the present invention.
[0050] FIG. 15 is a flow chart depicting a procedure of operations
of a video coding device which is the first embodiment of the
present invention.
[0051] FIG. 16 is a flow chart depicting a procedure of operations
of a video coding device which is the first embodiment of the
present invention.
[0052] FIG. 17 depicts an example of decomposing image components
into subbands in the second embodiment of the present
invention.
[0053] FIG. 18 depicts a relationship between coefficients of
respective components in the second embodiment of the present
invention.
[0054] FIG. 19 depicts an example of an integrated component unit
used in the second embodiment of the present invention.
[0055] FIG. 20 depicts another example of an integrated component
unit used in the second embodiment of the present invention.
[0056] FIG. 21 depicts an example of subband decomposition and an
integrated component unit used in the third embodiment of the
present invention.
[0057] FIG. 22 depicts another example of subband decomposition and
an integrated component unit used in the third embodiment of the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0058] Prior to explaining preferred embodiments of the present
invention, prior art video coding device and video decoding device
will be described below as references for the present
invention.
[0059] Recently, there has been proposed a subband coding method
that can efficiently encode and decode video signals. The
well-known high-efficient subband encoding method is used to
decompose an input image into such frequency bands as shown in FIG.
1B by a bank of band-decomposing filters as shown in FIG. 1A. The
band-decomposing filter-bank shown in FIG. 1A is a one-dimensional
filter-bank that can serve as a two-dimensional band-decomposing
filter-bank by repeating processing the input image in horizontal
and vertical directions. This method was reported by Fujii,
Noumura. "Topics on Wavelet Transform" in a Report of "TECHNICAL
REPORT of IEICE, IE92-11, 1992".
[0060] In FIG. 1A, there is shown a subband image obtained by
conducting two-dimensional subband decomposition three times. The
first two-dimensional subband decomposition obtains a horizontal
high-pass and a vertical low-pass band, a horizontal low-pass and
vertical high-pass band and a horizontal and vertical high-pass
band, which are designated by HL1, LH1 and HH1 respectively. A
horizontal and vertical low-pass band obtained by the first
decomposition is further subjected to two-dimensional
band-decomposition by which three subbands HL2, LH2 and HH2 are
obtained.
[0061] A horizontal and vertical low-pass subband obtained by the
second decomposition is further subjected to third two-dimensional
subband decomposition by which three subbands HL3, LH3 and HH3 and
a horizontal and vertical low-pass subband LL3 are obtained. A
Wavelet-converting filter-bank or a band-decomposing and
synthesizing filter-bank may be used as the band-decomposing
filter-bank. Thus, the decomposed subband-images are of a
hierarchical (layer) structure from low-frequency band to
high-frequency band.
[0062] Progressive image transmitting can be easily realized
utilizing the hierarchical structure of the subband images. As
shown in FIG. 2, the progressive image transmitting method enables
a video decoding device to reproduce a low-resolution image by
using only a part of coded data. The more coded data is reproduced,
the higher resolution the decoded image has. Japanese Laid-Open
Patent Publication (TOKKAI HEI) No. 8-242379 describes a system
(referred hereinafter to as a prior art system) to realize the
progressive image transmitting, which structure is shown in FIGS. 3
and 4.
[0063] FIG. 3 shows a video coding device using in the prior art
system and FIG. 4 shows a video decoding device using the system.
The video coding device as shown in FIG. 3 comprises a subband
decomposing portion 2001 for decomposing an input image into
subband images by using two-dimensional decomposing filters, a
coefficient coding portion 2002 for encoding coefficients of the
decomposed subband images, a variable-length coding portion 2003
for performing variable-length coding of the coded coefficient data
from the coefficient coding portion 2002 and a line-transmitting
portion 2004 for transmitting a plurality of components composing
the image per line at a time. The coefficient coding portion 2002
performs encoding the coefficients by using any one of various
kinds of coding methods (e.g., DPCM coding, zero-tree coding, and
scalar-quantizing coding). This process includes a quantizing
step.
[0064] The operation of the line transmitting portion 2004 will be
described below in detail, by way of example, with an input image
composed of three-components Y (a luminance component) and U, V
(chrominance components) and being conducted subband decomposition
three times as shown in FIG. 1B. Processing starts from a subband
LL3 shown in FIG. 1B, which gives the lowest resolution of the
image.
[0065] As shown in FIG. 5, the line-transmitting portion 2004
transmits the components Y, U and V sequentially line by line in
the order from the first line of the subband LL3. Having
transferred all lines of the subband LL3, the portion transfers the
components Y, U and V in the subbands LH3, HL3 and HH3 respectively
in the order: the component Y on the first lines of the subbands
LH3, HL3 and HH3; the component U on the first lines of the
subbands LH3, HL3 and HH3; the component V on the first lines of
the subbands LH3, HL3 and HH3; the component Y on the second lines
of the subbands LH3, HL3 and HH3; U on the second lines of LH3, HL3
and HH3; V on the second lines of the subbands LH3, HL3 and HH3 and
so on. Having transmitted all lines of LH3, HL3 and HH3, the line
transmitting portion transfers, in similar way, lines of LH2, HL2,
HH2 and, then, lines of LH1, HL1, HH1. The above-mentioned
procedure of the line-transmitting portion 2004 is illustrated by a
flowchart of FIG. 6.
[0066] Orderly transmission of the components Y, U, V composing the
image per line produces coded data having a hierarchical
structure.
[0067] Referring to FIG. 4, the video decoding device comprises a
line receiving portion 2004 for receiving the coded data from the
line-transmitting portion 2004 of the video-coding device of FIG. 3
and rearranging the data to respective component groups, a
variable-length decoding portion 2101 for decoding the rearranged
variable-length-coded data, a decoded data counting portion 2102
for counting bits of data decoded by the variable-length decoding
portion, a decoding truncating portion 2103 for comparing the
number of the bits counted by the decoded-data counting portion
with a preset threshold or an externally-given threshold to give a
command for stopping the decoding operation of the variable-length
decoding portion 2101 when the number of decoded bits exceeds the
threshold, a data completing portion 2105 for compensating for lack
of truncated data by adding zero when having truncated the decoding
the coded data at the specified number of bits, a coefficient
decoding portion 2106 for decoding coded coefficient data by
reversing the same processing procedure of the coefficient coding
portion 2002 of FIG. 3 and a subband synthesizing portion 2107 for
synthesizing an image from the subbands through two-dimensional
synthesizing filters.
[0068] The video decoding device can thus reproduce an entire image
from coded data having a hierarchical structure or a part
thereof.
[0069] The conventional video-coding and video-decoding system can
realize progressive image transmitting by transmitting image
components per line in an ascending order starting from the
lowest-resolution band-image. However, the prior art system
encounters several inconvenient problems resulting from the fixed
transfer-unit of a line. For example, an image composed of
luminance component Y and chrominance components U and V may be
easier recognized by transmitting only the component Y before the
components U and V rather than transmitting all components as a
unit.
[0070] In this case, it is preferable to transfer the image
components subband by subband, not by line. Furthermore, it is
proved that an image composed of components R, G, B may be
reproduced with better subjective image-quality at the decoding
terminal when coded coefficients of the respective components R, G
and B are transmitted one by one. This is because these components
have substantially almost the same influence on the visual
property.
[0071] The prior art system presumes that components of an image
have the same size. Therefore, it cannot be adaptable to an input
image composed of different sizes of components in format of, e.g.,
4:2:2 or 4:2:0.
[0072] Furthermore, the prior art system presumes that respective
components of an image have the same number of subbands and cannot
be adaptable to an input image whose components are decomposed into
different numbers of subbands.
[0073] Referring now to accompanying drawings, a video-coding
device and a video decoding device according to the present
invention will be described below in detail.
[0074] FIG. 7 is a block diagram showing a video coding device
which is a first embodiment of the present invention. As shown in
FIG. 7, the first embodiment of the present invention includes a
subband decomposing portion (subband decomposing means) 101, a
coefficient coding portion (coefficient coding means) 102 and a
variable-length coding portion (variable-length coding means) 103,
which are similar in construction to portions 2001, 2002 and 2003,
respectively, of FIG. 3.
[0075] In FIG. 7, numeral 104 designates a transfer-order deciding
and rearranging portion (rearranging means) that decides an
integrated component unit prepared by combining luminance or
chrominance elements from coded coefficient data provided from the
coefficient coding portion 102 and arranges coded coefficient data
of subbands in a transmitting order starting from the coded
coefficient data of the lowest-resolution subband. Whereas the
prior art video-coding device rearranges coded coefficient data in
the transmitting order after variable-length coding of the data,
the video-coding device according to the present invention
rearranges the coded coefficient data in the transmitting order
before variable-length coding of the data.
[0076] This makes it possible to conduct variable-length coding of
the coded coefficient data by, e.g., an arithmetic coding method
besides the Huffman coding method. According to the present
invention, it is also possible to conduct rearrangement of the
coded coefficient data after variable-length coding as the prior
art device does. The operation of the first embodiment is described
below with an input image composed of three components Y
(luminance), U (chrominance) and V (chrominance), which is the same
as that used in the prior art device. In this embodiment, these
components have the same resolution, i.e., the same image
sizes.
[0077] An integrated component unit may be prepared from
coefficient-coded data by combining elements Y, U and V. The
following example is an integrated component unit that is prepared
of subbands of Y, U and V.
[0078] FIG. 9 shows coefficients of subband images obtained through
performing three times of subband-decomposition of respective image
components Y, U and V ((a), (b) and (c) part of FIG. 9,
respectively). The image sizes of the components Y, U and V are
equal to each other. FIGS. 10 and 11 show the order of transmitting
the subband image coefficients of Y, U and V ((a), (b) and (c) part
of both of FIG. 10 and FIG. 11) in FIG. 9, respectively. Characters
Y, U and V with numeral suffixes in both of FIGS. 10, 11 denote the
order of transmitting subbands of respective components.
[0079] In the first embodiment, an integrated component unit is
composed of subbands and contains a set of the same-resolution
subbands of respective components, that is: (Y.sub.i, U.sub.i,
V.sub.i) where i=1 to 10 (the order of subbands to be
transferred).
[0080] The transmitting order is as follows: (Y.sub.1, U.sub.1,
V.sub.1), (Y.sub.2, U.sub.2, V.sub.2), . . . , (Y.sub.10, U.sub.10,
V.sub.10).
[0081] In the case of FIG. 10, a coefficient of high resolution in
a horizontal direction is transferred before a coefficient of high
resolution in vertical direction, while in the case of FIG. 11, a
coefficient of high resolution in a vertical direction is
transferred before a coefficient of high resolution in horizontal
direction. Accordingly, the resolution of the image reproduced at
the decoding side can be improved first in the horizontal direction
in the case of FIG. 10 and first in the vertical direction in the
case of FIG. 11.
[0082] Processing of coefficients within a subband may be performed
in any of the orders shown in FIG. 12.
[0083] The subband is horizontally scanned from above left to below
right (part designated by (1) of FIG. 12) or vertically scanned
from above left to below right (part (2) of FIG. 12) or scanned
spirally from the center of the subband to the outside thereof
(part (3) of FIG. 12). In FIG. 12, coefficients in a subband are
processed by one scanning as shown in each part (a) of parts (1) to
(3) and coefficients in a subband are processed by scanning twice
as shown in each parts (b) and (c) of the parts (1) to (3)
respectively.
[0084] In part (c) in FIG. 12, each arrow shows a coefficient or a
set of plural (t) coefficients. A set of (t) coefficients is
transferred in the direction indicated by the arrow, a subsequent
set of (t) coefficients is not transferred and a further subsequent
set of (t) coefficients is transferred in the direction indicated
by the arrow. This steps are repeated in first scanning process.
The coefficients left not-transferred in the first scanning process
(shown as arrows with real lines) are transferred in the second
scanning process (shown as arrows with broken lines) in the similar
way as in the first scanning process.
[0085] As shown in parts (4) and (5) of FIG. 12, it is also
possible to process coefficients of a subband by scanning three or
more times. For example, a horizontal interval and a vertical
interval between coefficients to be processed by n-th scan are
expressed as dx and dy respectively. If dx=dy=1, all coefficients
are encoded by one raster scan. If dx=dy=2 and horizontal and
vertical positions of codable coefficients are determined as (y,
x), the first scan encodes coefficients at the positions (0, 0),
(0, 2), (0, 4) . . . (2, 0), (2, 2), (2, 4) . . . (4, 0), (4, 2),
(4, 4) . . . ;
[0086] the second scan encodes coefficients at the positions (0,
1), (0, 3), (0, 5) . . . (2, 1), (2, 3), (2, 5) . . . (4, 1), (4,
3), (4, 5) . . . ;
[0087] the third scan encodes coefficients at the positions (1, 0),
(1, 2), (1, 4) . . . (3, 0), (3, 2), (3, 4) . . . (5, 0), (5, 2),
(5, 4) . . . ;
[0088] the fourth scan encodes coefficients at the positions (1,
1), (1, 3), (1, 5) . . . (3, 1), (3, 3), (3, 5) . . . (5, 1), (5,
3), (5, 5). In short, all coefficients are encoded by four
scans.
[0089] By generalizing this process as (dx=DX, dy=DY), the first
scan in case of part (1) in FIG. 12 encodes coefficients, as shown
part (4) in FIG. 12 at the positions of (0, 0), (0, DX), (0, 2*DX)
. . . ;
[0090] the second scan encodes coefficients at the positions (0,
1), (0, DX+1), (0, 2*DX+1) . . . ;
[0091] the third scan encodes coefficients at the positions (0, 2),
(0, DX+2) . . . (0, 2*DX+2) . . . ;
[0092] . . .
[0093] DX round scan encodes coefficients at the positions (0,
DX-1), (0, 2*DX-1), (0, 3*DX-1) . . . ;
[0094] (DX+1) round scan encodes coefficients at the positions (1,
0) (1, DX), (1, 2*DX) . . . ;
[0095] (DX+2) round scan encodes coefficients at the positions (1,
1) (1, DX+1), (1, 2*DX+1) . . . ;
[0096] (DX*DY) round scan encodes coefficients at the positions
(DY-1, DX-1) (DY-1, 2*DX-1), (DY-1, 3*DX-1) . . . (2*DY-1, DX-1)
(2*DY-1, 2*DX-1), (2*DY-1, 3*DX-1). In short, all coefficients are
encoded by (DX*DY) scans. Part (2) in FIG. 12 is reverse to part
(1) in FIG. 12 as to vertical and horizontal directions. The
coefficients can be processed by scanning as shown in part (5) FIG.
12 at horizontal and vertical intervals of (dx=DX, dy=DY).
[0097] In comparison with coefficients encoded by raster scanning
from the top left of a frame, the subband coefficients encoded by
scanning at intervals provided between the respective coefficients
can reproduce an image whose content can be recognized at an
earlier stage of decoding and which image can give better
subjective impression by the effect of gradually improving the
quality of the decoded image.
[0098] An example of an integrated component unit containing a
plurality of subbands included in the respective components is
described below. FIG. 13 shows another transmitting order of
coefficients of the subband image of FIG. 9. In a part of (b) of
FIG. 13, there is presented an example of encoding a subband image
in four layers. Blocks (Y.sub.2, Y.sub.3, Y.sub.4), (U.sub.2,
U.sub.3, U.sub.4) and (V.sub.2, V.sub.3, V.sub.4) of in the part
(b) of FIG. 13 consist each of three (m=3) subbands as shown in a
part (a) of FIG. 13.
[0099] Namely, three subbands (1, 2, 3) shown in the part (a) of
FIG. 13 correspond to one element set in an integrated component
unit. As these three subbands are treated as one element, three
coefficients having the, same relative positions in respective
three subbands are treated as one set as shown in a part (c) of
FIG. 13.
[0100] Three coefficients existing at the same relative positions
in the respective three subbands in FIG. 13 are supposed as one
coefficient, i.e., a (coefficient Y.sub.HL1, coefficient Y.sub.LH1,
coefficient Y.sub.HH1) are represented by a (coefficient Y.sub.4).
The component Y in each of the layers shown in the part (b) of FIG.
13 is transferred first in the scanning order shown in FIG. 12.
Similarly, the component U is transferred next and the component V
is then transferred. Coefficients of subband images of the same
resolution levels in horizontal, vertical and diagonal directions
are transmitted together from the coding side, so the resolutions
of a reproduced image in horizontal, vertical and diagonal
directions are increased at a time at the decoding side.
[0101] According to another method for treating three subbands as
one element, a subband 1 is first transmitted completely, a subband
2 is then transmitted completely and a subband 3 is finally
transmitted. Referring to FIG. 13, the subband 1 of the component Y
is transmitted in the scanning order shown in FIG. 12. Next, the
subband 2 of the component Y is transmitted in the same scanning
order and then the subband 3 of the component Y is transmitted in
the same scanning order. Subsequently, the subbands 1, 2 and 3 of
the component U are transmitted one by one in the same scanning
order as that for the component Y. Finally, the subbands 1, 2 and 3
of the components V are transmitted one by one in the same scanning
order as that for the component Y.
[0102] An integrated component unit includes elements (the subband
1 of the component Y, the subband 2 of the component Y, the subband
3 of the component Y, the subband 1 of the component U, the subband
2 of the component U, the subband 3 of the component U, the subband
1 of the component V, the subband 2 of the component V, the subband
3 of the component V). In this case, resolution of an image
reproduced at a decoding side is increased in a horizontal
direction, vertical direction and diagonal direction in the
described order. Transmission of these three subbands in the order
of subband 2, subband 1 and subband 3 causes an increase in
resolution of the image in the horizontal, vertical and diagonal
directions in the described order at the decoding side.
[0103] Several examples of transmitting subband coefficients may be
selectably used. In case if a codable image is known to be of
higher resolution in a specified direction, coefficients of a
subband in the known high-resolution direction are transferred
first at the coding side and the transferring order is rearranged
at the decoding side to earlier reproduce the coefficients of the
subband image in the known high-resolution direction. This makes it
possible to increase the quality of images in the decoding process
at the decoding side. In this instance, it is necessary to inform
the decoding side of the transmitting order in which coefficients
are encoded by placing such information in the coded data.
[0104] The transmitting-order deciding/rearranging portion 104
shown in FIG. 7 decides integrated component units (in the case of
FIG. 9) to be of subbands (Y.sub.i, U.sub.i, V.sub.i), where i=1 to
10 indicating the order of transmitting subbands), rearranges
subbands in the order of (Y.sub.1,U.sub.1,V.sub.1),
(Y.sub.2,U.sub.2,V.sub.2), . . . , (Y.sub.10,U.sub.10,V.sub.10) as
shown in FIGS. 10 and 11 or in the order of
(Y.sub.1,U.sub.1,V.sub.1), (Y.sub.2,U.sub.2,V.sub.2), . . . ,
(Y.sub.4,U.sub.4,V.sub.4) as shown in the part (b) of FIG. 13 and,
then, outputs the rearranged coefficient-coded data to the
variable-length coding portion 104.
[0105] Although the above-mentioned embodiment treats all
coefficients in a subband as one group, it may also prepare an
integrated component unit by using a coefficient or a plurality of
coefficients in a subband as a group. The following example treats
one line in a subband as a group of coefficients.
[0106] FIG. 14 shows an integrated component unit consisting of
horizontal lines one in each of the subbands, which is expressed as
follows:
[0107] (Y.sub.i(y),U.sub.i(y),V.sub.i(Y)), where Y.sub.i(y),
U.sub.i(y), V.sub.i(y) are one-line data of respective subbands Y,
U and V, i=1 to 10 indicates the order of transferring subbands and
y denotes each line number in subbands.
[0108] In this instance, the order of transferring the integrated
component units is as follows: (Y.sub.1(0), U.sub.1(0),
V.sub.1(0)), (Y.sub.1(1), U.sub.1(1), V.sub.1(1)), . . . ,
(Y.sub.2(0), U.sub.2(0), V.sub.2(0)), (Y.sub.2(1), U.sub.2(1),
V.sub.2(1)), . . . , . . . , (Y.sub.10(10), U.sub.10(0),
V.sub.10(0)), (Y.sub.10(1), U.sub.10(1), V.sub.10(1)), . . . .
[0109] In FIG. 14, an integrated component unit consists of
horizontal lines one in each of the subbands, which corresponds to
the scanning order shown in the part (a) of part (1) of FIG. 12.
Besides this, it is also possible to prepare an integrated
component unit composed of vertical lines one in each of the
subbands as shown in the part (a) of part (2) of FIG. 12. In this
instance, components Y, U, V may be expressed each by one arrow.
This processing is done on all subbands in the order shown in FIG.
10, FIG. 11 or the part (b) of FIG. 13.
[0110] It is also possible to prepare an integrated component unit
composed of coefficients one in each of the subbands, which is
expressed as:
[0111] (Y.sub.i(y,x), U.sub.i(y,x), (V.sub.i(y,x)), where
Y.sub.i(x,y), U.sub.i(x,y), V.sub.i(x,y) are coefficients one in
respective subbands Y, U and V, i=1 to 10 indicates the order of
transferring subbands, y denotes a position in vertical direction
in a subband, x denotes a position in horizontal direction in a
subband. In this instance, the transmitting order may be any of the
orders shown in parts (1), (2) and (3) of FIG. 12. The processing
is made on all subbands in the order shown in FIGS. 10, FIG. 11 or
the part (b) of FIG. 13.
[0112] FIG. 15 is a flow chart depicting an example of the
operation of the transmitting order deciding and rearranging
portion 104 of FIG. 7. In the shown case, the integrated component
unit may be changed over from the subbands to coefficients (one or
more groups of coefficient) or vice versa. The portion may be
designed to operate by using only one of the two units.
[0113] The video coding device according to the first embodiment of
the present invention can prepare coded data having a hierarchical
structure by decomposing an input image composed of a plurality of
components Y, U and V into subband images and encoding the subband
images in an ascending order of their resolution starting from the
lowest-resolution subband.
[0114] In comparison with the conventional device that integrates
components Y, U and V according to only the scanning line base, the
first embodiment of the present invention can perform adaptive
encoding input video data in view of the data characteristics by
applying integrated component units according to subband-based
and/or coefficient-based integration of the components Y, U and
V.
[0115] Referring now to FIG. 8, a video decoding device embodying
the present invention will be described below in detail. This video
decoding device is intended to decode video data prepared by the
video coding device according to the first embodiment of the
present invention.
[0116] In FIG. 8, the video-decoding device comprises a
variable-length decoding portion (variable-length decoding means)
201, a decoded-data counting portion (decoded data counting means)
202, a decoding truncating portion (decoding truncating means) 203,
a data completing portion (data completing means) 205, a
coefficient decoding portion (coefficient decoding means) 206 and a
subband synthesizing portion (subband synthesizing means) 207.
These portions are similar in construction to the portions a
variable-length decoding portion 2101, a decoded data counting
portion 2102, a decoding truncating portion 2103, a data completing
portion 2105, a coefficient decoding portion 2106 and a subband
synthesizing portion 2107, respectively, of FIG. 4.
[0117] In FIG. 8, numeral 204 designates a component separating
portion (component separating means, arranging means) for
separating coefficient-coded data rearranged by the transfer-order
deciding and rearranging portion of the coding device into data for
respective components. The component separating portion 204
rearranges coded data into respective component groups Y, U and V
by inverting the procedure that the coding side did.
[0118] Accordingly, the component separating portion 204 has a
memory (not shown) for storing respective components Y, U and V.
This memory has basically the same capacity that the subband
decomposing portion 101 of the video coding device has. However,
this portion may be designed to separate an integrated component
unit into coefficients for respective component groups Y, U, V and
output the separated coefficients to the coefficient decoding
portion 206 on completion of separation of the integrated component
unit. In this instance, the portion may have the memory enough to
store the largest integrated-component unit only.
[0119] The component separating portion 204 may also be designed to
work by successively separating and outputting coefficients of an
integrated component unit to the coefficient decoding portion 206.
In this case, the component separating portion 204 may have a
memory enough to store a plurality of separated coefficients
irrespective of the size of any integrated component unit to be
separated. The separated coefficients outputted from the component
separating portion 204 are decoded by the coefficient decoding
portion 206 and then stored in a memory (not shown) of the
coefficient decoding portion 206. In this case, the coefficient
decoding portion 206 includes decoded-data arranging means.
[0120] Furthermore, it is also possible to write the decoded
coefficients in a memory (not shown) for storing
frequency-coefficients to be input into the subband synthesizing
portion 207.
[0121] As described above, the coefficients separated by the
component separating portion 204 may be stored in a variety of
memory means. For the convenience of further explanation, the
component separating portion 204 separates integrated component
units by writing separated coefficients in its memory having the
same capacity as the memory of the subband decomposing portion 204
of the video coding device has.
[0122] For example, an integrated component unit composed of
subband data (Y.sub.1,U.sub.1,V.sub.1) is decomposed into separate
elements Y.sub.1, U.sub.1 and V.sub.1 respectively. The separated
elements Y, U and V are written into corresponding subbands
positions in a memory. Next, a unit (Y.sub.2, Y.sub.2, V.sub.2) is
decomposed into separate elements Y.sub.2, U.sub.2 and V.sub.2 that
are then written in specified positions of the corresponding
subbands in the memory for storing Y, U and V. This processing is
done on all the subbands.
[0123] In this instance, the order of decoding coefficients in each
subband is the same as described the process shown in FIG. 12. For
example, the coding side performed scans as shown in the part (1)
of FIG. 12, so the decoding side must do scans as shown in the part
(1) of FIG. 12. The application of this scanning method causes an
image in the decoding process to have resolution increasing in the
order of raster scanning from the top left to the down right.
[0124] In a particular case when coefficients were encoded by
scanning with spacing between them as shown in the part (4) or (5)
of FIG. 12, an image being decoded can be easily recognized at an
earlier stage of decoding as compared with the raster scanned
image. The image may be gradually improved in resolution level, so
the image may have better subjective-image quality.
[0125] The operation of the component separating portion 204 when
processing an integrated component unit composed of one or more
groups (sets) of coefficients in subbands is as follows:
[0126] Assuming one line in a subband is considered as a group of
coefficients, an integrated component unit is expressed as
(Y.sub.i(y), U.sub.i(y), V.sub.i(y)) where Y.sub.i(y), U.sub.i(y),
V.sub.i(y) are one-line data of respective subbands Y, U and V,
i=1-10 (the order of transmitting subbands) and y designates a
position in a vertical direction in a subband.
[0127] Y.sub.i(y), U.sub.i(y), V.sub.i(y) are separated from each
other and written in positions <line y> of the corresponding
subbands i in the memory for storing Y, U and V. This processing is
done on all the lines in the subbands in the order from the
lowest-resolution subband to the highest-resolution subband.
[0128] When an integrated component unit is composed of
coefficients selected one from each subband, it is expressed as:
(Y.sub.i(y, x), U.sub.i(y, x), V.sub.i(y, x)) where Y.sub.i(y, x),
U.sub.i(y, x), V.sub.i(y, x) are single-coefficient data of
respective subbands Y, U and V, i=1-10 (the order of transmitting
subbands) and y designates a position in a vertical direction in a
subband and x designates a position in a horizontal direction in a
subband.
[0129] Elements Y.sub.i(y, x), U.sub.i(y, x), V.sub.i(y, x) are
separated from each other and written in positions (y, x) of a
coefficient of the corresponding subbands i in the memory for
storing Y, U and V. This processing is done on all the coefficients
in the subbands from the lowest-resolution subband to the
highest-resolution subband.
[0130] As described before referring to FIG. 12, the decoding side
applies the same coefficient-scanning method as the coding side
used even if an integrated component unit is selected by 1 line or
by one coefficient.
[0131] The separate coefficients outputted from the component
separating portion 204 are combined into respective component
groups Y, U and V and then treated as respective groups.
[0132] FIG. 16 is a flow chart depicting an exemplified operation
procedure of the component separating portion 204. In the instance
shown in FIG. 16, the integrated component unit may be changed over
from the subbands to coefficients (one or more groups of
coefficient) or vice versa. The portion 204 may be provided with
either one of the two integrated component units.
[0133] Referring to FIG. 8, the operation of the data completing
portion 205 will be described below in detail:
[0134] In this case, an integrated component unit is composed of
one-line data in a subband.
[0135] Now let us suppose that the decoding operation was stopped
by the action of the decoding truncating portion 203 because the
number of bits of the decoded data exceeded a threshold value when
data for instance one-line data of integrated component unit shown
in FIG. 14, e.g., (Y.sub.1(0), U.sub.1(0), V.sub.1(0)), . . . ,
(Y.sub.3(5), U.sub.3(5), V.sub.3(5)) has been decoded. In this
instance, coefficients of the subbands 1 and 2 and coefficients of
the first line to the fifth line of the subband 3 have been decoded
but the remaining parts have no coefficient.
[0136] Data completing portion 205 produces subband coefficients by
putting 0 in remaining vacant parts where no data exist. This
enables the coefficient decoding portion 206 and the subband
synthesizing portion 207 to normally perform subsequent processing
steps. Vacant data may also be replaced with any other value than
0. The provision of the decoded data counting portion 202, the
decoding truncating portion 203 and the data completing portion 205
enables the decoding side to truncate the decoding operation at any
position by user's request.
[0137] The data completing portion 205 do nothing while the number
of bits of the decoded data does not exceed the threshold value.
Accordingly, a maximally expressible value may be previously set as
the threshold value in case of decoding all the coded data. The
embodiment may be a system of FIG. 8, which in this instance omits
the decoded data counting portion 202, the decoding truncating
portion 203, the data completing portion 205.
[0138] The coded data of the hierarchical structure, which
represents an image composed of a plurality of components Y, U, V,
can be decoded at the decoding side. The coded data of the
hierarchical structure allows the progressive decoding the coded
data, whereby the quality of the entire reproduced image is
sequentially improved. As compared with the prior art method
limited to the integrated component units of lines one for each
component, the present invention enables the system to conduct a
variety of progressive reproduction of the coded image. For
example, the present invention method can uniformly improve the
resolution of the reproduced image in horizontal, vertical and
diagonal directions, whereas the prior art method improves the
image resolution in the horizontal direction before the other
directions.
[0139] A second embodiment of the present invention for coding and
decoding an image composed of components having different sizes is
described below. The second embodiment of the present invention is
similar in construction to the first embodiment except for the
operation of the transfer-order deciding and rearranging portion
104 (step of outputting an integrated component unit). Therefore,
the same portions as the first embodiment are not explained
further. Only the transfer-order deciding and rearranging portion
104 will be described below.
[0140] For example, a format of 4:2:0 in which components U and V
have a horizontal and vertical size being one-half that of the
component Y is used. FIG. 17 shows resultants of three times of
band-decomposition of each the component Y whose size is Y*X and
the components U and V whose respective size is Y/2*X/2. In this
case, the subbands U and V are each half the size of the component
Y in horizontal and vertical directions. Respective components Y, U
and V have the same number of subbands.
[0141] Accordingly, no problem arises with subband-based integrated
units when applying the same scanning method and the same
transmitting order as the first embodiment used. However, there may
be a trouble with an integrated component unit composed of one or a
plurality of coefficient.
[0142] The subbands Y, U, V are different in size each other, so
the large-sized component Y may have excess coefficients if an
integrated component unit is composed of the same number of
coefficients per subband as described before in the first
embodiment of the present invention. Therefore, the number of
coefficients per component to be included in an integrated
component unit is set according to the size ratio of respective
components if the components are different from each other in
size.
[0143] A part (1) of FIG. 18 shows the corresponding of
coefficients of respective components for an image in the format of
4:2:0 as shown in FIG. 17. As the components Y, U and V have the
same number of subbands per component, the order of transferring
the integrated component units is the same as shown in FIG. 10 for
the first embodiment of the present invention. In this instance,
the ratio of the horizontal and vertical lengths of the components
Y, U and V is of 2:1:1, so one coefficient of each component U or V
corresponds to 4 coefficients of the component Y. Accordingly, the
numbers of coefficients for the components Y, U, V to be included
in an integrated component unit is determined according to the
ratio of 4:1:1.
[0144] The integrated component units prepared on the basis of the
subbands of respective components contain coefficients of the
components Y, U and V at the ratio of 4:1:1 and are processed in
the same manner as described before for the first embodiment of the
present invention.
[0145] Accordingly, an integrated component unit for one line per
subband is prepared to contain two lines Y, one line U and one line
V as shown in FIG. 19 while an integrated component unit for a
coefficient group per subband is prepared to contain 2*2
coefficients Y, one coefficient U and one coefficient V as shown in
FIG. 20. In FIG. 19, numerals suffixed one to component data Y, U
and V indicate, by way of example, the order of transferring the
data within the respective integrated component units. The
integrated component units for Y, U and V are processed one by one
for one subband. On completion of processing one subband, the
process advances to processing another subband in the order shown
in the part (1) of FIG. 18. The order of transferring the subbands
may be either one of those shown in FIGS. 11 and the part (b) of
FIG. 13.
[0146] With differently sized components Y, U and V, the video
decoding side can decode the coded data transmitted from the coding
side by changing the numbers of data of components contained in an
integrated component unit according to the ratio of horizontal and
vertical sizes of the components and writing the data in the
corresponding positions in a memory.
[0147] The same scanning method and the same transferring order as
described for the first embodiment can be applied in this
embodiment when working with the subband-based integrated component
units.
[0148] The second embodiment of the present invention is similar in
construction and function to the first embodiment except for the
operation of the transfer-order deciding and rearranging portion
204 (step of separating an integrated component unit into
respective components and writing separated data in corresponding
subbands in a memory). Therefore, the further description is
omitted.
[0149] In the second embodiment of the present invention, it is
possible to give coded data a hierarchical structure even if
components of an image have different sizes. The decoding side can
decode entire decoded data and can also obtain an entire reproduced
image from a part of the coded data.
[0150] Although the second embodiment has been described with only
an image having components whose horizontal and vertical size ratio
is 2:1:1, it can treat other size ratios of image components in the
similar manner as described above.
[0151] A third embodiment of the present invention is adaptable to
the case of processing image components being different in size and
decomposed into different numbers of decomposition levels by the
subband decomposing portion 101 of FIG. 7. This embodiment of the
present invention is similar to the first embodiment except for the
operation of the transfer-order deciding and rearranging portion
104 (step of outputting an integrated component unit). Therefore,
the same portions are not explained further. Only the
transfer-order deciding and rearranging portion 104 will be
described below.
[0152] Referring to FIG. 21, this embodiment is described by way of
example with an input image whose components U and V have
horizontal and vertical lengths being one half of those of the
component Y. A part designated by (1) of FIG. 21 shows the results
of decomposing the component Y three times and the components U and
V twice respectively. As the number of subbands of Y differs from
that of U and V, the third embodiment cannot use the transferring
methods described for the first and second embodiments and so uses
the following method of transferring the subbands.
[0153] An integrated component unit composed of subbands of
respective components Y, U and V is first described. In this
instance (first example), combinations of three-component subbands
Y, U and V, prepared from sevens of low-resolution subbands of
respective components Y, U and V as shown in a part (2) of FIG. 21,
are transferred one by one to the variable-length coding portion
103 of FIG. 7, then three remaining subbands of the component Y are
transferred independently one by one to the variable-length coding
portion 103. In short, each one of low-resolution subbands of
respective components Y, U and V, zero pieces of high-resolution
subbands of the components U and V and only one of high-resolution
subband of the component Y compose respective integrated component
units to be output.
[0154] Accordingly, the transferring order is expressed as
(Y.sub.1,U.sub.1,V.sub.1), (Y.sub.2,U.sub.2,V.sub.2), . . . ,
(Y.sub.7,U.sub.7,V.sub.7), (Y.sub.8), (Y.sub.9), (Y.sub.10).
[0155] In this instance, the subbands of respective Y, U, V
component (Y.sub.i, U.sub.i,V.sub.i), where i=1 to 7 designates the
transferring order, have the same sizes, so the same scanning
method as used in the first embodiment can be applied to the case
that integrated component unit is subbands or one or more groups of
coefficient.
[0156] Subbands of components Y, U and V are combined by threes as
shown in the part (b) of FIG. 13 to form combinations:
[0157] (Y.sub.1,U.sub.1,V.sub.1), (Y.sub.2,Y.sub.3,Y.sub.4,
U.sub.2,U.sub.3,U.sub.4, V.sub.2,V.sub.3,V.sub.4), (Y.sub.5,
Y.sub.6,Y.sub.7, U.sub.5,U.sub.6,U.sub.7, V.sub.5,V.sub.6,V.sub.7),
(Y.sub.8), (Y.sub.9), (Y.sub.10).
[0158] Another example (second example) is shown in FIG. 22. The
subband images shown in a part (1) of FIG. 22 are obtained as the
result of decomposing the component Y three times and the
components U and V twice respectively. In this instance, integrated
component units to be transmitted are formed by combining a set of
four low-resolution subbands Y with two low-resolution subbands U
and V as shown in a part (2) of FIG. 22 and by combining
high-resolution subbands of the components Y, U and V with each
other by ones as shown in a part (3) of FIG. 22.
[0159] The order of transferring the subbands is as follows:
(Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4, U.sub.1, V.sub.1), (Y.sub.5,
U.sub.2, V.sub.2), (Y.sub.6, U.sub.3, V.sub.3) (Y.sub.7, U.sub.4,
V.sub.4), (Y.sub.8, U.sub.5, V.sub.5), (Y.sub.9, U.sub.6, V.sub.6),
(Y.sub.10, U.sub.7, V.sub.7).
[0160] In the second example, three components have corresponding
subbands having different sizes, so the same scanning method as
used in the second embodiment can be applied to each integrated
component unit.
[0161] Subbands (Y.sub.5, Y.sub.6, Y.sub.7) shown in the part (3)
of FIG. 22 corresponds to a vertical-resolution subband, a
horizontal-resolution subband and a diagonal-resolution subband
respectively and have the same resolution levels. Therefore, each
integrated component unit can be prepared by combining respective
high-resolution subbands of respective components Y, U and V by
threes for each component. This is the third example of preparing
an integrated component unit. Similarly, an integrated component
unit may be prepared of combinations (Y.sub.8, Y.sub.9, Y.sub.10),
(U.sub.2, U.sub.3, U.sub.4), (U.sub.5, U.sub.6, U.sub.7), (V.sub.2,
V.sub.3, V.sub.4), (V.sub.5, V.sub.6, V.sub.7).
[0162] In this instance, the transmitting order is as follows:
(Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4, U.sub.1, V.sub.1), (Y.sub.5,
Y.sub.6, Y.sub.7, U.sub.2, U.sub.3, U.sub.4, V.sub.2, V.sub.3,
V.sub.4), (Y.sub.8, Y.sub.9, Y.sub.10, U.sub.5, U.sub.6, U.sub.7,
V.sub.5, V.sub.6, V.sub.7).
[0163] In the above-described example, subbands Y.sub.1, Y.sub.2,
Y.sub.3, Y.sub.4, U.sub.1, V.sub.1 are selected as a plurality of
low-resolution subbands with keeping the size ratio of Y, U and V
(in this example, the horizontal and vertical size ratio is 2:1:1).
Besides the above combination, Y.sub.1, Y.sub.2, . . . , Y.sub.7,
U.sub.1, . . . , U.sub.4, V.sub.1 . . . , V.sub.4 may also be
selected as a plurality of the low-resolution subbands.
[0164] A further fourth example which is another variety of
above-mentioned second or third example is such that the lowest
resolution subbands Y, U, V is extracted from respective groups of
low-resolution subbands Y.sub.1, Y.sub.2, . . . , Y.sub.7, U.sub.1,
. . . , U.sub.4, V.sub.1 . . . , V.sub.4 for respective components
and separately transferred as shown in a part (4) of FIG. 22 and a
set of remaining low-resolution subbands is then transferred like
second or third example. In this instance, the set of the
low-resolution subbands is a combination of six Y-component
subbands, three U-component subbands and three V-component subbands
as shown in a part (5) of FIG. 22. After transmission of all the
low-resolution subbands, high-resolution subbands shown in a part
(6) of FIG. 22 are transferred.
[0165] In the case of combining subbands one for each component
(corresponding to the second example), the order of transferring
the subbands is as follows: (Y.sub.1, U.sub.1, V.sub.1), (Y.sub.2,
Y.sub.3, Y.sub.4, Y.sub.5, U.sub.2, V.sub.2), (Y.sub.6, U.sub.3,
V.sub.3), (Y.sub.7, U.sub.4, V.sub.4), (Y.sub.8, U.sub.5, V.sub.5),
(Y.sub.9, U.sub.6, V.sub.6), (Y.sub.10, U.sub.7, V.sub.7).
[0166] In the case of combining subbands by threes for each
component (corresponding to the third example), the order of
transferring the subbands is as follows: (Y.sub.1, U.sub.1,
V.sub.1), (Y.sub.2, Y.sub.3, Y.sub.4, Y.sub.5, Y.sub.6, Y.sub.7,
U.sub.2, U.sub.3, U.sub.4, V.sub.2, V.sub.3, V.sub.4), (Y.sub.8,
Y.sub.9, Y.sub.10, U.sub.5, U.sub.6, U.sub.7, V.sub.5, V.sub.6,
V.sub.7).
[0167] For components having subband decomposition levels of not
less than 4, subbands having resolution levels higher than that of
a subband shown in a part (6) of FIG. 22 are the same in quantity
for components Y, U and V. In this instance, integrated component
units composed each of a combination of the same number of subbands
Y, U, V are subsequently transmitted.
[0168] In the above examples from first to fourth, the transmitting
order of the three subbands which have the same resolution levels
in horizontal, vertical and diagonal directions shall not be
restricted. In other words, for three subbands which have the same
resolution levels as shown in a part (a) of FIG. 13, the
transmitting order of these three subbands may be not only
subband1, subband2, subband3, but also subband2, subband1,
subband3, for example.
[0169] In the first example, the video decoding side can decode the
coded data received from the coding side by separating components
in each integrated component unit into groups of respective
components Y, U and V, writing separated data in the corresponding
subband areas in the memory and finally writing three
highest-resolution subbands in the corresponding subband area of
the memory.
[0170] In the second example, the video decoding side can decode
the coded data received from the coding side by separating the
subbands in each integrated component unit by reversing the process
made by the coding side and writing the subbands of each component
in the corresponding subband area in the corresponding memory. In
this case, the third embodiment differs from the first and second
embodiments by the fact that only the first integrated component
unit is prepared from a plurality of the low-resolution subbands by
the coding side and contains four subbands Y, one subband U and one
subband V.
[0171] As described above, the number of low-resolution subbands to
be combined with each other can be freely selected. For example, an
initial integrated-component unit may contain seven Y-component
subbands, four U-component subbands and four V-component
subbands.
[0172] In the third example, each integrated component unit can be
decomposed into subbands of respective components Y, U and V by the
same method as described for the second example and written into
corresponding subband areas (for Y, U and V components) in the
memory for decoding them. Since the high-resolution subbands Y, U
and. V have been combined by threes in an integrated component unit
at the coding side, the high-resolution subbands Y, U and V are
recorded by threes for each component in corresponding subband
areas in the memory for decoding them. This example differs from
the second example by the above-mentioned feature.
[0173] In the fourth example, the video decoding side can decode
the coded data received from the coding side by separating the
subbands in each integrated component unit in the same manner as
shown for decoding device in second or third example and writing
the subbands of each component in the corresponding subband area in
the corresponding memory. This example differs from the second and
third examples by the fact that the lowest-resolution subbands of
the respective components Y, U, V are first stored in the
corresponding subband areas (Y, U, V) in the memory for decoding
and then low-resolution subbands other than the lowest-resolution
subbands are stored in the corresponding areas (Y, U, V) in the
memory.
[0174] The video decoding device according to the third embodiment
of the present invention is similar to that of the first embodiment
except for the operation of the component separating portion 204
(step of separating each integrated component unit into respective
components and writing the separated data in the corresponding
areas in a memory). Therefore, further explanation is omitted.
[0175] With integrated component units each composed of one or more
groups of coefficients such as lines instead of the subbands for
respective components Y, U and V, the third embodiment can apply
the same process as described before with the same case in the
first and second embodiments based upon the same method as
described for the integrated component unit composed the subbands
for the respective components Y, U and V.
[0176] In the third embodiment of the present invention, an image
whose components have different sizes and different decomposition
levels can be encoded so that coded data having a hierarchical
structure is obtained at the coding side and an entire image is
reproduced from the entire coded data or a part of the coded data
at the decoding side.
[0177] Although the third embodiment has been described by way of
example with only an image having components whose size ratio is of
2:1:1, it can treat other size ratios of image components in the
similar manner as described above. For example, an image whose
components Y, U and V are the same in size and have different
numbers of subbands can be encoded to have a hierarchical structure
through the same process as described above in the third
embodiment. The transmitting orders corresponding to those shown in
FIGS. 11 and 13 are also adopted besides the described order of
FIG. 10.
[0178] The three embodiments of the present invention have been
described by way of example with the specified order of
transferring the elements Y, U, V in the integrated component units
but shall not be limited to that order.
INDUSTRIAL APPLICABILITY
[0179] The present invention brings following advantageous
effects.
[0180] Firstly, the video coding device and the video decoding
device according to the present invention operate with integrated
component units whose elements are all frequency coefficients in m
(m>1) respective subbands of respective component A.sup.n and
can therefore transmit and decoded first specified subbands of the
image components that may be components Y, U and V and have
different levels of influence on human visual property, allowing
one to recognize an essence of the image at an earlier stage of
decoding at the decoding side. When a codable image is known to be
of higher resolution in a specified direction, the coding device
can transmit first coded coefficients of
higher-resolution-direction subbands and the decoding device can
decode those coded coefficients, and even in case of terminating
the decoding in the midway of decoding all coded data, can thereby
reproduce the image from only data decoded till that time to
improve subjective-image quality of the image.
[0181] Secondly, the video coding device and the video decoding
device according to the present invention operate with integrated
component units whose elements are m (m>1) pieces of frequency
coefficients having the same relative positions in m (m.gtoreq.1)
respective subbands of respective components A.sup.n and can decode
those coded coefficients, and even in case of terminating the
decoding in the midway of decoding all the coded data, can thereby
reproduce the image from only the data decoded till that time to
improve subjective-image quality of the image when the image is
composed of components R, G and B that have substantially almost
the same influence on human visual property.
[0182] Thirdly, the video coding device and the video decoding
device according to the present invention can be adapted to process
an image whose luminance and chrominance components are different
from each other by resolution, having a great advantage over the
conventional method that can be applied to an image whose
components have the same resolution. This feature provided by the
present invention is very desirable in particular to digital image
processing since many digital images are usually formatted to have
higher resolution of the luminance component than that of
chrominance component.
[0183] Fourthly, the video coding device and the video decoding
device according to the present invention can be adapted to process
an image whose luminance and chrominance components are different
from each other by resolution and have different
subband-decomposition levels, getting a great advantage over the
conventional method that can be applied to an image whose
components have the same resolution and the same number of
subbands. This feature provided by the present invention is very
desirable in particular to digital image processing since many
digital images are usually formatted to have higher resolution of
the luminance component than that of chrominance component and it
is general to use the different subband-decomposition levels
according to the components' resolution levels.
[0184] Fifthly, the video coding device and the video decoding
device according to the present invention can be adapted to process
an image whose luminance and chrominance components have different
resolution levels and different subband-decomposition levels,
getting a great advantage over the prior art method that can be
applied to an image whose components have the same resolution and
the same number of subbands. Furthermore, these aspects of the
present invention provide such a feature that each integrated
component unit always reflects the ratio of the number of
respective components contained in an input image. This feature
eliminates the need for decoding, redundant data at the decoding
side when decoding the amount of data according to the resolution
of the display unit.
[0185] Sixthly, in addition to the fifth advantageous effect
above-mentioned, the video coding device and the video decoding
device according to the present invention can first separate and
transmit lowest-resolution subbands of respective components
A.sup.n to first present the summary of an image, making it
possible to improve subjective quality of the reproduced image.
* * * * *