Bit rate coder for differential quantization
First Claim
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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Accused Products
Abstract
A feed-forward bit-rate control system that selects and formats DQUANT values in real time for optimal semantically-encoded image transmission by video-compression codecs complying with the ITU-T standards H.263 or H.263E. The system uses a prequantization process to reduce the computational load imposed by the quantizer optimization calculations required for feed-forward semantic coding bit-rate control. The H.263 CBPY and MCBPC coding tables are reordered so as to be indexed using an orthogonal flag-based index values and the RLA coding table is block-indexed using clipped amplitude values, for faster access into these tables. The system also uses a rate-assist process to assure that DQUANT values are provided in each edge macroblock that follows a transition to and from each semantically-defined region when the edge macroblocks have four motion vectors by reducing the number of motion vectors in the macroblock to one.
149 Citations
12 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for line-by-line feed forward bit-rate control of a differentially quantized signal representing an array of blocks, said array having a given number of lines and given number of blocks in each line, each of said blocks being in a region, each region having a respective set of available quantizer values for quantizing data values in said blocks, said method comprising the steps of:
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iteratively determining a bit rate for each block in each line in a frame; determining when the calculated bit rate for the frame exceeds a given target rate; 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; 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; bypassing the computation 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. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification