Standardization activities on multimedia coding in ISO
- Hiroshi Yasuda
- Sig. Proc.: Image Comm.
Natural-image coding schemes may be classified into four families: pelwise, blockwise, region-based and model-based. The pelwise and blockwise classifications include many mature still-picture and moving-picture techniques that now form the basis of image coding standards [I]. These include predictive and transform coding, vector quantization, conditional replenishment, and motion compensatiodinterpolation. Compression ratios for intraframe coding of 8-bit greyscale images (i.e. luminance only) are typically between 4:1 and 12:l. Color picture compression ratios are about twice as high, because the raw data comprises three 8-bit components, but, when compressed, the color adds relatively little overhead. More extreme compression is possible when temporal redundancy can be exploited with interframe coding of moving pictures, but this is only available in applications like videoconferencing where large movements happen infrequently.