Image analysis – Image compression or coding – Interframe coding
Patent
1998-08-11
2000-11-28
Couso, Jose L.
Image analysis
Image compression or coding
Interframe coding
382238, G06K 936
Patent
active
061545708
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and an apparatus for coding digital image signals, a method and an apparatus for decoding coded digital image signals, and data recording media containing programs for making a computer execute coding processing and decoding processing of digital image signals and, more particularly, to time/space hierarchical coding processing of an image of an object having the arbitrary shape, and time/space hierarchical decoding processing corresponding thereto.
BACKGROUND ART
In order to store/transmit digital image information with good efficiency, it is required to perform compressive coding to the digital image information and, in the present circumstances, there are Discrete Cosine Transformation (DCT) which is representative in JPEG (Joint Photographic Coding Experts Group) and MPEG (Moving Picture Experts Group), and waveform coding methods such as subband, wavelet and fractal, as methods for compressively coding the digital image information.
As a method for removing redundant image information between adjacent pictures such as frames, there is a method of performing inter-picture prediction using motion compensation, that is, representing pixel values of pixels of the present picture using a difference between these pixel values and pixel values of pixels of the previous picture, and performing waveform coding to this difference signal.
Recently, in order both to improve compression efficiency and to regenerate an image signal for each of regions constituting one picture and corresponding to individual objects (hereinafter referred to as image spaces), a method of compressively coding an image signal object by object and transmitting the resulting signal has been made practicable. In this method, at the side of regeneration, coded image signals corresponding to individual objects are decoded, images of the individual objects regenerated by decoding are composed, thereby displaying an image corresponding to one picture. In this way, object-by-object coding of an image signal enables images of objects to be displayed to be freely combined and composed, whereby moving pictures can be easily reedited. Further, in this method, according to the congestion conditions of channels, the performance of a regenerative apparatus, and the viewer's taste, moving pictures can be displayed without regenerating images of relatively unimportant objects.
More specifically, as methods for coding an image signal for forming image space including an image of an object having the arbitrary shape (hereinafter referred to as an object image), there are conventionally a coding method using a transformation method adaptive for its shape (for example, shape adaptive discrete cosine transformation), and a coding method of padding pixel values of pixels constituting an invalid region of an image space (that is, an outside region of an object image) by a specified method, and then performing cosine transformation to an image signal comprising plural pixel values corresponding to the image space, for each of unit regions into which the image space is divided (blocks comprising 8.times.8 pixels).
As a specific method for removing a redundant signal between pictures such as frames, there is a method of using macroblocks comprising 16.times.16 pixels as unit regions, obtaining a difference between an image signal corresponding to a target macroblock as a target of coding processing and its prediction signal. Herein, the prediction signal is an image signal corresponding to a prediction region which is obtained by motion compensation. The motion compensation is processing of detecting a region comprising 16.times.16 pixels, the region providing an image signal having the smallest difference with the image signal of the target macroblock, in a picture which has been subjected to coding processing or decoding processing, as the prediction region.
However, when this prediction region is located at the boundary of the object image in the image space, the prediction region includes pixels w
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Orchad, "Predictive Motion-Field Segmentation for Image Sequence Coding", IEEE Transaction on Circuits and Systems for Video Technology, vol. 3, No. 1, pp. 54-70, Feb. 1993.
Kronander, "Post and Pre-Processing in Coding of Image Sequences Using Filters with Motion Compensated History", IEEE Acoustics, Speech, and Signal Processing, vol. 2, pp. 1104-1107, 1988.
Couso Jose L.
Do Anh Hong
Matsushita Electric - Industrial Co., Ltd.
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