Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1989-11-29
1990-10-16
Britton, Howard W.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
375122, 381 31, H04N 713
Patent
active
049630300
ABSTRACT:
Blocks of an image or voice input signal are decimated by a selected factor d, (e.g., d=2) and distributed through a plurality (d.sup.2) of ordered channels for vector quantization coding using a codebook in which vectors are ordered, such as by their average intensity. The first channel makes a full search of stored vectors in the codebook for a best match and outputs the index m.sup.(1) of the best match. The second channel makes a partial search for a best match over a localized region of the codebook around the index m.sup.(1) and outputs the index m.sup.(2) of the best match. The subsequent channels make partial searches over a smaller localized region of the codebook around an index that is a function of the indices m.sup.(1) and m.sup.(2). At the decoder, the indices m.sup.(1), m.sup.(2), m.sup.(3) and m.sup.(4) are used to look up vectors in a codebook identical to the coder codebook. These vectors are then assembled by a process that is the inverse of the decimation and distribution process at the encoder to output a decoded signal that is high quality replica of the input signal. The narrow search ranges in the channels following the first reduce the encoding search time and bit rate for each of the input blocks. That range may be readily changed for each channel, and therefore may be made adaptive.
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Gray, Robert M., "Vector Quantization," IEEE ASSP Mag., vol. 1, No. 2, Apr. 1984, pp. 4-29.
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Aravind, R. et al., "Low-Rate Image Coding with Finite-State Vector Quantization," Proc. Intl. Conf. ASSP, 1986, pp. 137-140.
Westerink, P. H. et al., "Subband Coding of Images Using Vector Quantization," IEEE Trans. on Comm., vol. 36, No. 6, June 1988, pp. 713-719.
Britton Howard W.
California Institute of Technology
Fernandez Antonio M.
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