Two stage residual lattice based vector quantization

A two-stage image compression scheme is proposed. It is shown that, with this scheme considerable improvement can be achieved over standard JPEG. Two different schemes are presented. In the first scheme, each block is converted into DCT coefficients. The low frequency coefficients are quantized using a high rate lattice based vector quantizer (LVQ) in the first stage. In the second stage, the residue of this image is quantized with an LVQ. The results are comparable with that of the standard JPEG. In the second scheme, we use a standard JPEG, with a low bit rate, for the first stage and the residue of image is again quantized with an LVQ in the second stage. With this method the PSNR is improved by up to 4 dB in comparison to the standard JPEG at moderate bit rates.<
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