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Bit rate coder for differential quantization

  • US 6,088,392 A
  • Filed: 05/30/1997
  • Issued: 07/11/2000
  • Est. Priority Date: 05/30/1997
  • Status: Expired due to Fees
First Claim
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1. Apparatus for line-by-line feed forward bit-rate control of a differentially quantized signal representing a frame having an array of blocks, said frame having a given number of lines and given number of blocks in each line, each of said blocks having a data value and being in a region, each region having a respective set of available quantizer values for use in quantizing said data value in a block, said apparatus comprising:

  • bit-rate calculating means for iteratively determining a bit rate for each block in each line in the frame;

    bit-rate control means for determining when the calculated bit rate for the frame exceeds a given target rate;

    quantizer adjustment means for reducing the quantizer for one region in a next line when the calculated bit rate for the frame does not exceed said given target rate;

    rate-assist means for reducing four motion vectors to one in edge blocks of the one region that follow blocks in another region and forcing coding of a respective quantizer change value; and

    a bypass path for bypassing said bit rate calculation means for preventing determination of a bit rate for a block where a respective maximum value in each block is not greater than the respective quantizer value used in a given iteration for quantizing the data value in said block.

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