Successive approximation quantization with generalized decoding for wavelet transform image coding

A novel combination of a successive approximation scalar quantizer encoder structure and a direct sum decoder structure is introduced. The encoder structure is a multiple level free structure that corresponds to a conventional uniform scalar quantizer. The decoder structure is a multiple stage direct sum structure. The uniform quantizer encoder structure is matched to the dynamic range of the source output. The decoder direct sum structure is jointly optimized for the source probability density function and the fixed partition of the uniform quantizer encoder. The bit stream generated by the encoder can be decoded either by the standard uniform quantizer decoder, or by the generalized nonuniform direct sum decoder described. Successive approximation multiple stage scalar quantizers with both standard and generalized decoders are tested on image wavelet transform coefficients. The generalized codes give approximately 0~7 dB improvements over standard codes for one to eight bit representations of real-valued wavelet coefficients