NOISE-REDUCTION AND CONCEALMENT FOR BLOCK ENCODED

A simple scheme to detect the presence of the channel noise on the vec tor quantized images are proposed. The channel noise effect is removed or concealed by utilizing the continuity of the image signal and the availability of the complete code-book at the receiver. Several coding techniques (such as channel-optimized vector quantization and vector quantization with pseudo-Gray coding) are tested. It is found that the proposed technique always improves the image quality under noisy chan nel. In addition, it provides the best image quality when vector quant ization with pseudo-Gray coding is used as the coding technique. Under this scheme, the proposed technique provides 0.2-1.2 dB performance g ain (in average) for a binary symmetric channel with bit error rate 0. 1-1%, respectively.