Patent ID: 7738555

Claim:
An encoder that encodes a signal into macroblocks, each macroblock comprising up to four luminance blocks and up to two chrominance blocks, and organizes the macroblocks and quantization data into a bitstream such that the macroblocks may be decoded according to a method comprising: determining a quantization parameter from the quantization data in the bitstream; generating a luminance scalar according to a first piece-wise linear transformation of the quantization parameter, wherein the first piece-wise linear transformation is selected from the group consisting of: the luminance scalar equals 8 whenever the quantization parameter falls within the values 1 through 4, inclusive, the luminance scalar equals 2 times the quantization parameter whenever the quantization parameter falls within the values 5 through 8, inclusive, the luminance scalar equals the quantization parameter plus 8 whenever the quantization parameter falls within the values 9 through 24, inclusive, and the luminance scalar equals 2 times the quantization parameter minus 16 whenever the quantization parameter falls within the values 25 through 31, inclusive; for each of the up to four luminance blocks that are members of the macroblock, inverse quantizing a DC coefficient of the luminance block by the luminance scalar; transforming data of the blocks, including the respective inverse quantized DC coefficient, according to an inverse discrete cosine transform; and merging via a processor data of the blocks to generate image data of the macroblock.