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Adaptive tree-search vector quantization in MPEG2 decoder

  • US 6,320,907 B1
  • Filed: 11/19/1998
  • Issued: 11/20/2001
  • Est. Priority Date: 11/24/1997
  • Status: Expired due to Term
First Claim
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1. A method for reducing a memory requirement for temporarily storing a stream of digital data blocks in a coding/decoding system of information transferable by blocks, such data being compressed and coded by blocks through a tree-search vector quantization (TSVQ) and stored in a memory, where a subsequent reading phase decompresses the data by reconstructing the coded and compressed digital data blocks, the method comprising the steps of:

  • a) fixing a certain scan path of each data block R (rows)×

    C (columns) of the stream of digital data blocks to be separated into vectors of preestablished dimensions;

    b) coding a first vector of a scan of a digital data block in an unmodified manner;

    c) partitioning in one or more regions the scanning of a generated R×

    C data block;

    d) selecting and calculating a complexity measure for each region as a mean value of a sum of absolute values of differences among corresponding components of adjacent vectors of the scanning, and belonging to the region;

    e) quantizing according to a binary tree-search in a table of quantized values of the complexity measure by coding a corresponding address and using the address for controlling a multiplexer selecting a plurality of tables of quantized vectors, sending the address to the multiplexer that conveys a properly compressed value to the memory;

    f) generating a predictor vector of the current one to be quantized, as a replica of a last decoded vector according to scanning and calculating of a prediction error vector;

    g) quantizing according to a binary tree-search in a read only table of quantized vectors the prediction error vector, the table being selected among the plurality of tables of quantized vectors by the address of the quantized measure, coding the address of the table and sending it to a multiplexer that subsequently conveys a compressed value to the memory;

    h) adding components of a vector read from the selected table of quantized vectors to the vector replica of the vector previously decoded, generating a prediction vector for a next vector to be coded according to the scanning path and the selected region;

    i) repeating steps d) through h) following the scanning path for all the regions that make up the R×

    C data block, and for all the scanning vectors of each input data block;

    j) premultiplying a read-only table using quantized complexity measures relative to centroids of a tree-like scheme used for the search, and producing as many precalculated tables for quantizing a prediction error of a physical parameter (luma, chroma) of the digital data block; and

    k) quantizing the prediction error using one of the precalculated tables selected by an address generated by estimating and quantizing a complexity measure of each one of the regions in which the R×

    C block is divided.

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