Variable-rate finite-state vector quantization of images

A description is given of two variable-rate finite-state vector quantization systems for low bit rate image coding. The first system subtracts the mean from each input block and then encodes the mean-subtracted block by means of the 2-D version of the variable-rate finite-state vector quantization system. The block-mean is separately encoded efficiently by exploiting the high correlation present in the means of the adjacent blocks. At a bit rate of 0.31 b/pixel, a peak signal-to-noise ratio of 31.66 dB is achieved for encoding the 512×512 version of the Lena image using this system. The second system is a generalization of the system described by Riskin, Daly, and Gray (see Proc. IEEE ICASSP, P.1735, 1989). A prediction is made on each pixel using a fifth-order predictor, and the residual is again encoded using the same type of finite-state vector quantization. A peak signal-to-noise ratio of 31.2 dB is achieved at 0.31 bits/pixel for encoding the 512×512 version of Lena using this system