Patrick A. Fleckenstein

Very fast JPEG compression using hierarchical vector quantization

We derive a JPEG compliant image compressor, which is based on hierarchical vector quantization (HVQ). The goal is to reduce complexity while increasing compression speed. For each block, the DCT DC coefficient is encoded in the regular way, while the residual is mapped through HVQ to a precomputed bit stream corresponding to the compressed DCT AC coefficients. Approximation quality is generally good for high compression ratios. Color Fax is one possible application target for the proposed system.

Signal processing using LUT filters based on hierarchical VQ

Vector quantization (VQ) is a powerful tool in signal processing. Hierarchical VQ (HVQ) is a method to implement VQ completely based on look-up tables (LUT). In HVQ, both encoders and decoders are inherently simple and fast, since there are no searches over codebooks. We introduce an overlapped HVQ (OHVQ) method, in which the number of samples is preserved after each HVQ stage. After the last stage, each OHVQ code in a particular location in the signal maps to a block (vector) which approximates that neighbourhood in the original sequence. For this reason, OBVQ is used as a basis to create a LUT-based filter, ie, a spatial signal processor with very fast implementation. Preliminary analysis and image processing examples are shown demonstrating the efficiency of the proposed method.

Fast JPEG encoding for color fax using HVQ

We derive a JPEG compliant image compressor which is based on hierarchical vector quantization (HVQ). The goal is to reduce complexity while increasing compression speed. For each block, the DCT DC coefficient is encoded in the regular way while the residual is mapped through HVQ to a pre-computed bit-stream corresponding to the compressed DCT AC coefficients. Approximation quality is generally good for high compression ratios. Color Fax is the primary application target for the proposed system.