Adaptive compression of digital video data using different modes such as PCM and DPCM

A method for selecting compression modes for different portions of data to be transmitted, comprising the steps of:

• compressing a plurality of said portions using first, second, and third different compression modes;
• accumulating said plurality of portions compressed using said first compression mode together with first overhead data to provide a first set of accumulated data;
• accumulating said plurality of portions compressed using said second compression mode together with second overhead data to provide a second set of accumulated data;
• accumulating, together with third overhead data to provide a third set of accumulated data, said plurality of portions each compressed using whichever of said compression modes meets a first selection criterion for that portion, said first selection criterion basing its selection on the amount of compressed data for each of said portions after accounting for selection data included in said third overhead data;
• comparing the first, second and third sets of accumulated data to determine which set meets a second selection criterion based on the amount of accumulated data in said sets;
• and
• providing said plurality of portions for transmission in a compressed form determined by whichever one of said first, second and third sets of accumulated data meets said second selection criterion.

Decoder apparatus comprising:

• means for receiving superblocks of compressed video data, said superblocks containing individual blocks each compressed using one of a plurality of compression modes;
• means coupled to said receiving means for retrieving, from each received superblock, one of:
• first overhead data indicative of a first compression mode used to compress the whole received superblock,
• second overhead data indicative of a second compression mode used to compress the whole received superblock, and
• third overhead data indicating that the individual blocks contained in the received superblock were compressed using a plurality of different compression modes;
• means responsive to said first overhead data for decoding the received superblock using a decompression mode corresponding to said first compression mode;
• means responsive to said second overhead data for decoding the received superblock using a decompression mode corresponding to said second compression mode;
• and
• means responsive to said third overhead data for identifying the compression mode used to compress each individual block in the received superblock and for decoding the received superblock using a decompression mode for each of said individual blocks that corresponds to the compression mode used to compress the block.