A finite state/frame difference interpolative vector quantizer for low rate image sequence coding

A finite-state vector quantizer (VQ) suitable for both intraframe and interframe coding is presented. Interblock and interframe memory is expressed through a state variable driven by an improved classifier which keys on the intensity gradients of a block´s neighbours and its own interframe motion. A bilinear interpolator reduces the energy of foreground residuals encoded by the quantization, improving edge rendition and limiting blocking artifacts. Background blocks are vector predictive coded using simple frame differencing and codebooks built with a gradient design algorithm. The codec at 0.4 bit/pixel outperforms a similar but non-finite-state intraframe VQ at 1.0 bit/pixel by 4 dB