Adaptive entropy-coded subband coding of image sequences

A new approach to image sequence coding based on variable-rate entropy-constrained subband coding (ECSBC) is described. The corresponding practical implementation of the ECSBC scheme for fixed-rate channels is developed by extending recent adaptive entropy-coded (AEC) quantization techniques. Although the entropy-constrained design of subband coding systems provides improve coding efficiency compared to level-constrained design approaches, the resulting coding system generates variable-rate outputs which must be buffered before fixed-rate transmissions. In this case, the finite buffer, however large, that interfaces the encoder and the channel will eventually overflow or underflow, resulting in a catastrophic loss of encoder-decoder synchronism with an associated large amount of distortion. A buffer-adaptive arithmetic-coded implementation of the ECSBC scheme, called adaptive entropy-coded subband coding (ECSBC/AEC), is described to completely eliminate the associated encoder buffer overflow/underflow problems, even with a very small encoder buffer. >