Still image coding using predictive tree-VQ with sub-band decomposition

The combination of a linear-predictive still-image coding scheme with tree encoding and vector quantization (predictive tree-VQ, PTVQ) is applied to subband decomposed images. PTVQ allows the use of large codeword lengths and produces good image quality at bit rates around 0.3 b/pixel. Schemes with and without local bit-rate adaptation are studied. All combinations of PTVQ and subband coding (SBC) show good performance with regard to signal-to-noise-ratio (SNR) and perceptual quality criteria and outperform the original PTVQ as well as simple SBC-DPCM (differential pulse-code modulation) schemes, even at rates as low as 0.2 b/pixel