Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2001-06-07
2004-11-02
Lee, Young (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240250
Reexamination Certificate
active
06813314
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Description of Related Art
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”.
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 HL
1
, LH
1
and HH
1
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 HL
2
, LH
2
and HH
2
are obtained.
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 HL
3
, LH
3
and HH
3
and a horizontal and vertical low-pass subband LL
3
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.
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.
A video coding device using the prior art system includes 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.
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.
1
B. Processing starts from a subband LL
3
, which gives the lowest resolution of the image.
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 LL
3
. Having transferred all lines of the subband LL
3
, the portion transfers the components Y, U and V in the subbands LH
3
, HL
3
and HH
3
respectively in the order: the component Y on the first lines of the subbands LH
3
, HL
3
and HH
3
; the component U on the first lines of the subbands LH
3
, HL
3
and HH
3
; the component V on the first lines of the subbands LH
3
, HL
3
and HH
3
; the component Y on the second lines of the subbands LH
3
, HL
3
and HH
3
; U on the second lines of LH
3
, HL
3
and HH
3
; V on the second lines of the subbands LH
3
, HL
3
and HH
3
and so on. Having transmitted all lines of LH
3
, HL
3
and HH
3
, the line transmitting portion transfers, in similar way, lines of LH
2
, HL
2
; HH
2
and, then, lines of LH
1
, HL
1
, HH
1
. The above-mentioned procedure of the line-transmitting portion is executed according to a programed flow.
Orderly transmission of the components Y, U, V composing the image per line produces coded data having a hierarchical structure.
The prior art video decoding device includes 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.
The video decoding device can thus reproduce an entire image from coded data having a hierarchical structure or a part thereof.
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.
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.
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.
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.
SUMMARY OF THE INVENTION
The present invention is directed to a system for effective progressive image transmitting by solving the foregoing problems involved in the prior arts.
(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≧2) kinds of luminance or chrominance components into subband images for each of components A
n
(1≦n≦N, where n is an integer) composing an image to be coded, coef
Aono Tomoko
Katata Hiroyuki
Kusao Hiroshi
Saiga Hisashi
Birch & Stewart Kolasch & Birch, LLP
Lee Young
Sharp Kabushiki Kaisha
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