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US 5,426,463 AGranted
Apparatus for controlling quantizing in a video signal compressor
AssigneeRCA Thomson Licensing Corporation
InventorsDaniel J. Reininger, Ajanta Guha
Life of this patent
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Abstract
A rate controlled VBR quantizing system includes a quantizer for quantizing partially compressed video data and further apparatus for monitoring the amount of compressed output data. Dependent upon the amount of compressed output data being lesser or greater than a predetermined value, the quantizer is conditioned to operate in a fixed quantization mode, or a mode wherein only selected blocks of data in respective frames are adaptively quantized, respectively.
Claims17
Apparatus for quantizing video signal occurring in frames with respective frames being divided into a plurality of blocks of codewords, said apparatus comprising:
- a source of said blocks of codewords;
- means for determining the volume of coded data for respective said blocks of codewords, said coded data corresponding to said blocks of codewords being quantized with a predetermined quantizing factor;
- means for providing a threshold value which is a function of an average or mean volume of coded data for a plurality of said blocks;
- comparing means for determining whether the volume of coded data in respective blocks of codewords is greater or lesser than said threshold value;
- and
- means for quantizing the blocks of codewords corresponding to blocks of codewords whose volume of coded data is less than said threshold value according to a further predetermined quantizing factor selected to provide reproduced images with predetermined image quality, and for adaptively quantizing blocks of codewords corresponding to blocks of codewords whose volume of coded data exceeds said threshold value, with still further quantizing factors to provide greater quantization than said further predetermined quantizing factors, and wherein said further predetermined quantizing factor may be equal to said predetermined quantizing factor.
3 more elements
Apparatus for quantizing video signal occurring in frames with respective frames being divided into a plurality of blocks of codewords said apparatus comprising:
- a source of said blocks of codewords:
- means for determining the volume of coded data for respective said blocks of codewords when quantized with a predetermined quantizing factor;
- means for statistically analyzing the volume of coded data from a predetermined plurality of said blocks of codewords;
- means responsive to statistics provided by such statistical analysis for generating a threshold value;
- comparing means for determining whether the volume of coded data in respective blocks of codewords is greater or lesser than said threshold value;
- and
- means for quantizing the blocks of codewords corresponding to blocks of codewords whose volume of coded data is less than said threshold value according to a further predetermined quantizing factor selected to provide reproduced images with predetermined image quality, and for adaptively quantizing blocks of codewords corresponding to blocks of codewords whose volume of coded data exceeds said threshold value, with still further quantizing factors to provide greater quantization than said further predetermined quantizing factors, and wherein said further predetermined quantizing factor may be equal to said predetermined quantizing factor.
4 more elements
A method for quantizing partially compressed video signal occurring in blocks of codewords, a plurality of such blocks of codewords representing a frame of video signal, said method comprising:
- generating coded data for respective said blocks of codewords corresponding to Said blocks of codewords being quantized with a predetermined quantizing factor;
- determining a threshold value as a function of the average or mean volume of coded data in respective said blocks of codewords over a plurality of said blocks of codewords;
- comparing the volume of coded data for respective blocks of codewords against said threshold value;
- quantizing blocks of codewords having a volume of coded data less than said threshold value with a further predetermined quantizing factor selected to provide variable bit rate coded data which will provide reproduced images with a predetermined image quality;
- and
- adaptively quantizing blocks of codewords having a volume of coded data greater than said threshold value with quantizing factors which produce coarser quantization than said further predetermined quantizing factor, and wherein said further predetermined quantizing factor may equal said predetermined quantizing factor.
3 more elements
A method for quantizing partially compressed video signal occurring in blocks of codewords, a plurality of such blocks of codewords representing a frame of video signal, said method comprising:
- generating coded data for respective said blocks of codewords corresponding to said blocks of codewords being quantized with a predetermined quantizing factor;
- determining one of the mean or average volume E{b} of coded data for the blocks of codewords in said plurality of blocks of codewords;
- determining the standard deviation of the volume STD{b} of coded data for said plurality of blocks of codewords;
- determining a threshold value ThV according to a function of the form,
- ThV=K.sub.1 (E{b})+K.sub.2 (STD{b})+K.sub.3
- where K.sub.1, K.sub.2, and K.sub.3 are constants;
- comparing the volume of coded data for respective blocks of codewords against said threshold value:
- quantizing blocks of codewords having a volume of coded data less than said threshold value with a further predetermined quantizing factor selected to provide variable bit rate coded data which will provide reproduced images with a predetermined image quality:
- and
- adaptively quantizing blocks of codewords having a volume of coded data greater than said threshold value, with quantizing factors which produce coarser quantization than said further predetermined quantizing factor, and wherein said further predetermined quantizing factor may equal said predetermined quantizing factor.
7 more elements
A method for quantizing partially compressed video signal occurring in blocks of codewords, a plurality of such blocks of codewords representing a frame of video signal, said method comprising:
- generating coded data for respective said blocks of codewords corresponding to said blocks of codewords being quantized with a predetermined quantizing factor;
- determining a threshold value, ThV, related statistically to the volumes of coded data in respective said blocks of codewords over a plurality of said blocks of codewords;
- comparing the volume of coded data for respective blocks of codewords against said threshold value;
- quantizing blocks of codewords having a volume of coded data less than said threshold value with a further predetermined quantizing factor selected to provide variable bit rate coded data;
- adaptively quantizing blocks of codewords having a volume of coded data greater than said threshold value with quantizing factors which produce coarser quantization than said further predetermined quantizing factor, wherein said further predetermined quantizing factor may equal said predetermined quantizing factor;
- and
- successively adjusting said threshold value after quantizing ones of said blocks of codewords according to an algorithm
- ThV.sub.n =.alpha..sub.n ThV
- where .alpha..sub.n is a variable updated for successive blocks n according to the relation
- .alpha..sub.n =.alpha..sub.n-1 -.gamma..sub.n K.sub.n-1
- K.sub.n-1 is related to a reduction in the total quantized data due to adaptive quantization of a predetermined number of previously quantized macroblocks and .gamma..sub.n is a variable dependent upon an accumulated amount of coded data.
8 more elements
Dependencies are inferred from the claim text.