Pyramid transform coding

The authors present a pyramid data structure in the block transform domain which reduces the correlation between blocks and is suitable for progressive image transmission. The transform difference pyramid is either scale or vector quantised and encoded on a level-by-level basis, where the residual coding errors introduced at one level are delivered to and reprocessed at the next level. The use of vector quantisation is seen to result in a considerable coding gain over variable-length coding. Reasonable subjective quality is achieved at a bit rate of about 0.125 bits/pixel, and excellent quality is achieved at a bit rate of about 0.55 bits/pixel. The simulation results demonstrate that the proposed pyramid transform coding scheme is competitive with variable-length coding on the original block DCT image.<>