Flexible quantization

A digital media processing method comprising:

• storing at least part of a bitstream representing compressed digital media data in a memory;
• and
• decoding the at least part of the bitstream by applying quantization parameters to transform coefficients of blocks of the digital media data and applying inverse operations of a transform to the blocks of the digital media data, wherein the quantization parameters are selectively variable across at least a spatial dimension, a frequency dimension, and a color channel dimension, and wherein the selective variability across each of the dimensions is signaled by signals in the bitstream.

A digital media processing method comprising:

• storing at least part of a bitstream representing compressed digital media data in a memory;
• and
• decoding the at least part of the bitstream by applying quantization parameters to transform coefficients of blocks of the digital media data and applying inverse operations of a transform to the blocks of the digital media data, wherein the quantization parameters applied to luminance coefficients and to chrominance coefficients are selectively variable between at least a first chrominance quantization mode in which the chrominance coefficients use the same one or more quantization parameters as the luminance coefficients and a second chrominance quantization mode in which the chrominance coefficients use different quantization parameters than the luminance coefficients.

A picture decoder device comprising:

• a data storage buffer for storing at least part of a bitstream of encoded picture data;
• and
• a processor programmed to decode the at least part of the bitstream by applying quantization parameters to transform coefficients of blocks of the picture data according to quantization rules selectively applied according to signals in the bitstream and applying inverse operations of a transform to the blocks of the picture data, the signals in the bitstream including a first signal for determining how a quantization rule is to be applied across a spatial dimension, a second signal for determining how a quantization rule is to be applied across a frequency dimension, and a third signal for determining how a quantization rule is to be applied across a color channel dimension.

A picture decoder device comprising:

• a data storage buffer for storing at least part of a bitstream of encoded picture data;
• and
• a processor programmed to decode the at least part of the bitstream by applying quantization parameters to transform coefficients of the blocks of the picture data and applying inverse operations of a transform to the blocks of the picture data, wherein the quantization parameters applied to luminance coefficients and to chrominance coefficients are selectively variable between at least a first chroma quantization mode in which the chrominance coefficients use the same one or more quantization parameters as the luminance coefficients and a second chroma quantization mode in which the chrominance coefficients use different quantization parameters than the luminance coefficients.

A digital media processing method comprising:

• encoding digital media data by applying operations of a transform to blocks of the digital media data and applying quantization parameters to transform coefficients of the blocks of the digital media data, wherein the quantization parameters are selectively variable across at least a spatial dimension, a frequency dimension, and a color channel dimension, and
• generating a bitstream of encoded digital media data, the bitstream further including signals for indicating how the quantization parameters were applied across the spatial dimension, the frequency dimension, and the color channel dimension.