Television – Bandwidth reduction system – Data rate reduction
Reexamination Certificate
1999-06-23
2001-08-07
Adams, Russell (Department: 2851)
Television
Bandwidth reduction system
Data rate reduction
C348S420100, C375S240160, C375S240240
Reexamination Certificate
active
06271885
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to highly efficient coding of analog moving picture signals to digital signals with a small amount of codes for efficient data transfer, storage and displaying. Particularly, this invention relates to motion-compensated coding of moving picture signals with motion vector variable encoding.
Moving picture signals are generally encoded by motion-compensated prediction according to encoding standards such as MPEG standards.
Motion vectors (MV) used for motion-compensated prediction are also encoded by variable-length coding and then multiplexed with codes of predictive error signals. Bit streams of multiplexed codes are transferred to decoders, stored into storage media or displayed on screen.
MV encoding is carried out by taking differences between motion vectors in a block of a moving picture signal and those in an adjacent block, and encoding the differences in horizontal and vertical directions by using variable-length codes. The variable-length codes consists of, for example, Huffman codes according to the frequency (the number of times) of generation of motion vector differences.
MV encoding generally uses one code table for variable-length encoding. The code table is composed of variable-length codes in accordance with MV difference distribution (probability of generation of each MV difference). MV differences have a big difference to each other according to motion of pictures, and MV difference distribution does not match a coding table depending on portions of a picture, thus increasing the amount of codes of motion vectors. Furthermore, the smaller the block of moving picture signal in motion compensation for high accuracy, the more the codes of motion vectors in the total amount of generated codes.
SUMMARY OF THE INVENTION
A purpose of the present invention is to provide an apparatus and a method of motion-compensated predictive coding of moving picture signals with motion vector variable coding for less generation of codes of motion vectors.
Another purpose of the present invention is to provide an apparatus and a method of motion-compensated predictive decoding of encoded moving picture signals and motion vectors.
The present invention provides an apparatus for encoding a moving picture signal by motion-compensated prediction using motion vectors for each motion-compensated block of the moving picture signal. The apparatus includes a vector grouping unit, a motion vector encoder and a multiplexer. The vector grouping unit arranges the motion vectors into motion vector groups for each predetermined number of motion vectors; a code table selector to select a code table among a plurality of code tables for each motion vector group for encoding the motion vectors and to output code table selection information. The motion vector encoder encodes the motion vectors by variable-length coding using the selected code table in response to the code table selection information. The multiplexer multiplexes the code table selection information and the encoded motion vectors.
Furthermore, the present invention provides a method of encoding a moving picture signal by motion-compensated prediction using motion vectors for each motion-compensated block of the moving picture signal. The motion vectors are arranged into motion vector groups for each predetermined number of motion vectors. A code table is selected among a plurality of code tables for each motion vector group for encoding the motion vectors and code table selection information is output. The motion vectors are encoded by variable-length coding using the selected code table in response to the code table selection information. The code table selection information and the encoded motion vectors are multiplexed.
The present invention further provides an apparatus for decoding a moving picture bit stream that has been encoded by motion-compensated prediction using motion vectors for each motion-compensated block of the moving picture. The apparatus includes a demultiplexer and a motion vector. The demultiplexer demultiplexes the moving picture bit stream into the motion vectors and code table selection information, the motion vectors having been encoded by variable-length coding using a code table selected among a plurality of code tables for each motion vector group in accordance with the code table selection information, the motion vectors having been arranged into motion vector groups for each predetermined number of motion vectors. The motion vector decoder decodes the motion vectors obtained by demultiplexing by variable-length decoding using the code table selected in accordance with the code table selection information obtained by demultiplexing.
Moreover, the present invention provides a method of decoding a moving picture bit stream that has been encoded by motion-compensated prediction using motion vectors for each motion-compensated block of the moving picture. The moving picture bit stream is demultiplexed into the motion vectors and code table selection information, the motion vectors having been encoded by variable-length coding using a code table selected among a plurality of coding tables for each motion vector group in accordance with the code table selection information, the motion vectors having been arranged into motion vector groups for each predetermined number of motion vectors. The motion vectors obtained by demultiplexing are decoded by variable-length decoding using the code table selected in accordance with the code table selection information obtained by demultiplexing.
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Adams Russell
Anderson, Kill & Olick P. C.
Fuller Rodney
Victor Company of Japan Ltd.
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