Appeal No. 2000-2247
Application 08/137,189
BACKGROUND
The invention relates to coding blocks of moving images,
such as in visual telephony. The prior art discloses three
coding modes: intra-image coding, inter-image coding, and
movement-compensated inter-image coding. Intra-image coding is
costly in terms of the number of bits transmitted, but must be
used, for example, upon transmission of the first image in a
sequence or upon abrupt changing of scenes. Intra-image coding
risks an overflow of the buffer memory. The invention provides a
fourth mode of inter coding which substitutes for the intra-image
coding mode. The coding mode codes the difference between a
current macroblock (at position bc in figure 3) and the most
similar of four adjacent macroblocks of the reconstructed current
image (positions br in figure 3). This makes it possible to
limit the use of strictly intra-image coding.
Claim 1 is reproduced below.
1. A method of coding of blocks of television images
including intra-image coding and differential coding wherein
said differential coding consists in coding a minimum
pixel-by-pixel difference between a current block of a
current image to be transmitted and one among four
reconstructed blocks of the same current image in a closest
vicinity of the current block, said one closest block being
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