Flexible quantization
First Claim
Patent Images
1. A method of decoding digital media, comprising:
- with a computer,receiving compressed digital image data, the compressed digital image data having been partitioned along more than one dimension;
determining multiple sets of quantization parameter indices from signals in the compressed digital image data, the compressed digital image data having been quantized across more than one partitioned dimension of the digital image data, the signals indicating whether quantization parameter indices used during decoding vary within a frequency band dimension and within a color channel dimension, the quantization parameter indices available across the frequency band dimension including, for a given set of the multiple sets of quantization parameter indices, a first quantization parameter index for one or more DC components, a second quantization parameter index for multiple low-pass components, and a third quantization parameter index for multiple high-pass components;
for each of multiple macroblocks of the compressed digital image data;
selecting one of the multiple sets of quantization parameter indices based on a value signaled for the macroblock; and
determining one or more quantization parameters for the selected set of quantization parameter indices;
dequantizing the compressed digital image data in accordance with the determined quantization parameters;
applying an inverse of a block transform to blocks of the dequantized digital image data; and
outputting decompressed digital image data,wherein;
(a) the multiple high-pass coefficients are AC coefficients from first transforms of values of blocks of a macroblock;
(b) the multiple low-pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms; and
(c) the one or more DC coefficients include a DC coefficient from the second transform of the DC coefficients from the first transforms.
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Abstract
A digital media encoder/decoder uses a flexible quantization technique that provides the ability to vary quantization along various dimensions of the encoded digital media data, including spatial, frequency sub bands and color channels. The codec utilizes a signaling scheme to signal various permutations of flexible quantization combinations efficiently for primary usage scenarios. When a choice of quantizer is available, the codec efficiently encodes the current quantizer by defining a subset of quantizers and indexes the current quantizer from the set.
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Citations
17 Claims
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1. A method of decoding digital media, comprising:
with a computer, receiving compressed digital image data, the compressed digital image data having been partitioned along more than one dimension; determining multiple sets of quantization parameter indices from signals in the compressed digital image data, the compressed digital image data having been quantized across more than one partitioned dimension of the digital image data, the signals indicating whether quantization parameter indices used during decoding vary within a frequency band dimension and within a color channel dimension, the quantization parameter indices available across the frequency band dimension including, for a given set of the multiple sets of quantization parameter indices, a first quantization parameter index for one or more DC components, a second quantization parameter index for multiple low-pass components, and a third quantization parameter index for multiple high-pass components; for each of multiple macroblocks of the compressed digital image data; selecting one of the multiple sets of quantization parameter indices based on a value signaled for the macroblock; and determining one or more quantization parameters for the selected set of quantization parameter indices; dequantizing the compressed digital image data in accordance with the determined quantization parameters; applying an inverse of a block transform to blocks of the dequantized digital image data; and outputting decompressed digital image data, wherein;
(a) the multiple high-pass coefficients are AC coefficients from first transforms of values of blocks of a macroblock;
(b) the multiple low-pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms; and
(c) the one or more DC coefficients include a DC coefficient from the second transform of the DC coefficients from the first transforms.- View Dependent Claims (2, 3, 4, 5, 6)
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7. A digital media processing device comprising:
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a memory for storing digital media data; and a digital media processor programmed to encode and/or decode the digital media data by applying forward or inverse operations of a transform to blocks of the digital media data, and applying quantizers to the blocks of digital media data, wherein the quantizers include a set of frequency band quantizers, the set of frequency band quantizers including; (a) an HP quantizer for multiple high-pass coefficients of a macroblock, wherein the multiple high-pass coefficients are AC coefficients from first transforms of values of blocks of the macroblock; (b) an LP quantizer for multiple low-pass coefficients of the macroblock, wherein the multiple low-pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms; and (c) a DC quantizer for a DC coefficient of the macroblock, wherein the DC coefficient is a DC coefficient from the second transform of the DC coefficients from the first transforms. - View Dependent Claims (8)
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9. At least one memory device or magnetic disk having program code stored thereon for causing a digital media processing device to perform a method of processing digital media data according to a codec, the method comprising:
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selecting combinations of available quantization modes to be applied to the digital media data, the available quantization modes including at least a first quantization mode in which low pass coefficients use the same quantizer as a DC coefficient and a second quantization mode in which high pass coefficients use the same quantizer as low pass coefficients, the first quantization mode being signaled by a first syntax element, the second quantization mode being signaled by a second syntax element; applying a two-stage transform to blocks of the digital media data; quantizing the digital media data according to the selected combinations of quantization modes; encoding the quantized digital media data in a compressed data stream; and signaling the selected combinations of quantization modes in the compressed data stream, the compressed data stream including the first syntax element and the second syntax element, wherein the high pass coefficients are AC coefficients from first transforms of values of the blocks, and wherein the low pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms. - View Dependent Claims (10, 11, 12, 13)
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14. At least one memory device or magnetic disk having program code stored thereon for causing a digital media processing device to perform a method of processing digital media data according to a codec, the method comprising:
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receiving compressed digital image data; determining multiple sets of quantization parameter indices from signals in the compressed digital image data, the signals indicating whether quantization parameter indices used during decoding vary within a frequency band dimension and within a color channel dimension, the quantization parameter indices available across the frequency band dimension including, for a given set of the multiple sets of quantization parameter indices, a first quantization parameter index for one or more DC components, a second quantization parameter index for multiple low-pass components, and a third quantization parameter index for multiple high-pass components; for each of multiple macroblocks of the compressed digital image data; selecting one of the multiple sets of quantization parameter indices based on a value signaled for the macroblock; and determining one or more quantization parameters for the selected set of quantization parameter indices; dequantizing the compressed digital image data in accordance with the determined quantization parameters; applying an inverse of a block transform to blocks of the dequantized digital image data; and outputting decompressed digital image data, wherein (a) the multiple high-pass coefficients are AC coefficients from first transforms of values of blocks of a macroblock;
(b) the multiple low-pass coefficients are AC coefficients from a second transform of DC coefficients from the first transforms; and
(c) the one or more DC coefficients include a DC coefficient from the second transform of the DC coefficients from the first transforms. - View Dependent Claims (15, 16, 17)
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Specification