Television – Bandwidth reduction system – Data rate reduction
Patent
1997-05-19
1999-08-10
Chin, Tommy P.
Television
Bandwidth reduction system
Data rate reduction
348409, 348416, H04N 712, H04N 1102, H04N 1104
Patent
active
059366702
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of decoding digital signals which correspond to images subdivided into fixed-size picture areas, called macroblocks, and have been transmitted and/or stored in the form of coded data corresponding to frames of I or P or B type. The I type being coded without using information from other frames, the P type being predicted by means of a motion-compensated prediction from an earlier reference frame and an associated motion information, and the B-type being bidirectionally interpolated from an earlier and a later reference frame of I or P type and associated motion information. Such decoding method includes for decoding of the macroblocks, the steps of: corresponding for each macroblock to its relevant parameters and the picture elements therein; obtained.
The invention also relates to a decoding device for the implementation of this of decoding digital signals which correspond to images subdivided into fixed-size picture areas, called macroblocks, and have been transmitted and/or stored in the form of coded data corresponding either to frames of I or B type, the I type being coded without using any information from other frames the P type being predicted by means of a motion-compensated prediction from an earlier reference frame and an associated motion information, the B type being bidirectionally interpolated from an earlier and a later reference frame of I or P type and associated motion information, said decoding device comprising: or B type; in accordance with the decoded data thus obtained; means.
Such an invention has an application in the field of digital television (either normal definition television or high definition television), and especially when television signals are compatible with the MPEG standard for digital moving picture decoding, the characteristics of which will not be described.
2. Description of the Related Art
The International Standardization Organisation (ISO) has developed over these last few years several digital data compression algorithms, and particularly the MPEG standard (MPEG, from Moving Picture Experts Group). This standard, provided for achieving compatibility between compression and decompression equipment and specifying both the coded digital representation of a video signal and the method of decoding, is based on two main techniques: an orthogonal transformation of the signals to be compressed, which allows to remove the spatial redundancy within each picture, and a motion compensation between pictures, which allows to remove the temporal redundancy in the sequence of pictures.
Motion compensation is a technique which consists in combining already coded pictures with data representative of the motion concerning these pictures. This technique, also called motion-compensated prediction, assumes that the current picture can be locally modeled as a translation of the picture at a previous time. The word "locally" means that the amplitude and the direction of the translation need not be the same everywhere in the picture. The pictures being subdivided into blocks, or into macroblocks including several blocks, the translation from one macroblock (for instance) of a previous picture to a corresponding macroblock of the current picture is described by a vector representative of the displacement between these macroblocks. The encoding process can then concern no longer the macroblock itself but an error macroblock obtained by subtraction between said previous and current macroblocks. An inverse decoding process allows to reconstruct the original pictures. Under the MPEG standard, the picture is divided into a series of slices, each of them containing a number of macroblocks. Each macroblock covers an area of 16.times.16 picture elements, or pixels, comprising itself four luminance blocks of 8.times.8 pixels and two chrominance blocks of 8.times.8 pixels, and the motion compensation is provided between the macroblocks of 16.times.16 pixels (by coding the motion of an entire macrob
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VLSI Implementation of MPEG Decoders by Thierry Fautier; pp. 164-172, May 1994.
Chin Tommy P.
Diep Nhon
U.S. Philips Corporation
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