Activity selective SPIHT coding

An embedded image coder that provides very eeective progressive image transmission and a high degree of spatial scalability while achieving superior visual performance to SPIHT is presented. A new partitioning structure combined with scale-based wavelet weights achieves a signiicance reordering that codes more signiicant information belonging to the lower frequency bands earlier in the bitstream when compared to SPIHT. This reordering provides substantial improvements in progressive transmission, spatial scalability, and PSNR, especially at low bit rates. Further visual gains are achieved by exploiting human visual system (HVS) characteristics to weight wavelet co-eecients according to their perceptual importance, causing a reordering of the coeecients. The activity selective SPIHT coder provides higher perceptual quality and higher PSNRs than SPIHT at low bit rates, and comparable visual quality with slightly lower PSNRs at high bit rates.