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US 2012/0069900 A1Published application
System, method and computer-readable medium for encoding a signal into macroblocks
AssigneeAT&T Intellectual Property II, L.P.
InventorsBarin Geoffry Haskell, Atul Puri, Robert Lewis Schmidt
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Abstract
A quantizer and dequantizer for use in a video coding system that applies non linear, piece-wise linear scaling functions to video information signals based on a value of a variable quantization parameter. The quantizer and dequantizer apply different non linear, piece-wise linear scaling functions to a DC luminance signal, a DC chrominance signal and an AC chrominance signal. A code for reporting updates of the value of the quantization parameter is interpreted to require larger changes when the quantization parameter initially is large and smaller changes when the quantization parameter initially is small.
Claims22
A decoder comprising:
- a processor;
- a computer-readable storage medium storing instructions, which, when processed by the processor, cause the processor to perform a method comprising:
- determining a quantization parameter from a bitstream;
- generating a luminance scalar according to a first piece-wise linear transformation of the quantization parameter, wherein:
- (i) the luminance scalar equals 8 whenever the quantization parameter falls within the values 1 through 4, inclusive;
- (ii) the luminance scalar equals 2 times the quantization parameter whenever the quantization parameter falls within the values 5 through 8, inclusive;
- (iii) the luminance scalar equals the quantization parameter plus 8 whenever the quantization parameter falls within the values 9 through 24, inclusive;
- and
- (iv) the luminance scalar equals 2 times the quantization parameter;
- inverse quantizing a DC coefficient of a respective luminance block of up to four luminance blocks by the luminance scalar to yield a respective inverse quantized DC coefficient;
- transforming data of the up to four luminance blocks, including the respective inverse quantized DC coefficient, according to an inverse discrete cosine transform;
- and
- merging data of the up to four luminance blocks to generate image data associated with a respective macroblock.
10 more elements
A decoder comprising:
- a processor;
- a computer-readable storage medium storing instructions, which, when processed by the processor, cause the processor to perform a method comprising:
- determining a quantization parameter from a bitstream;
- generating a chrominance scalar according to a first piece-wise linear transformation of the quantization parameter as follows:
- a) the chrominance scalar equals 8 whenever the quantization parameter falls within the values 1 through 4, inclusive;
- (b) the chrominance scalar equals (the quantization parameter+13)/2 whenever the quantization parameter falls within the values 5 through 24, inclusive;
- and
- (c) the chrominance scalar equals the quantization parameter minus 6 whenever the quantization parameter falls within the values 25 through 31, inclusive;
- inverse quantizing a DC coefficient of a respective chrominance block of the two chrominance blocks by the chrominance scalar to yield a respective inverse quantized chrominance DC coefficient;
- transforming data of the up to two chrominance blocks, including the respective inverse quantized chrominance DC coefficient, according to an inverse discrete cosine transform;
- and
- merging data of up to two chrominance blocks to generate image data associated with a macroblock.
9 more elements
A method comprising:
- (1) identifying a quantization parameter from a bitstream;
- (2) generating a luminance scalar according to a first piece-wise linear transformation of the quantization parameter as follows:
- (i) the luminance scalar equals 8 whenever the quantization parameter falls within the values 1 through 4, inclusive;
- (ii) the luminance scalar equals 2 times the quantization parameter whenever the quantization parameter falls within the values 5 through 8, inclusive;
- (iii) the luminance scalar equals the quantization parameter plus 8 whenever the quantization parameter falls within the values 9 through 24, inclusive;
- and
- (iv) the luminance scalar equals 2 times the quantization parameter;
- (3) inverse quantizing by the luminance scalar a DC coefficient of a respective luminance block of up to four luminance blocks to yield a respective inverse quantized DC coefficient;
- (4) transforming data of the blocks, including the respective inverse quantized DC coefficient, according to an inverse discrete cosine transform;
- and
- (5) merging data of the up to four luminance blocks to generate image data.
8 more elements
A method comprising:
- (1) identifying a quantization parameter from a bitstream;
- (2) generating a chrominance scalar according to a first piece-wise linear transformation of the quantization parameter as follows:
- (i) the chrominance scalar equals 8 whenever the quantization parameter falls within the values 1 through 4, inclusive;
- (ii) the chrominance scalar equals (the quantization parameter+13)/2 whenever the quantization parameter falls within the values 5 through 24, inclusive;
- and
- (iii) the chrominance scalar equals the quantization parameter minus 6 whenever the quantization parameter falls within the values 25 through 31, inclusive;
- (3) inverse quantizing a DC coefficient of a respective chrominance block of up to two chrominance blocks by the chrominance scalar to yield a respective inverse quantized DC coefficient;
- (4) transforming data of the up to two chrominance blocks, including the respective inverse quantized DC coefficient, according to an inverse discrete cosine transform;
- and
- (5) merging data of the up to two chrominance blocks to generate image data.
7 more elements
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