Using quality and bit count parameters in quality and rate control for digital audio
First Claim
1. A computer-readable storage medium storing computer-executable instructions for causing a computer programmed thereby to perform a method of controlling quality of information in a constant bitrate encoder, wherein the encoder outputs the information at variable quality and compressed to a constant or relatively constant bitrate, the method comprising:
- determining a target maximum-bits parameter based at least in part upon (a) a first value constraining how many bits can be used in trying to satisfy a target quality parameter for a current block of information and (b) a second value indicating a number of bits available in a buffer until overflow;
quantizing the current block of information to meet constant or relatively constant bitrate requirements, wherein, in a quality control quantization loop, the encoder adjusts quantization step size of the quantizing in view of a comparison of the target quality parameter for the current block to a quality measurement for the current block as quantized and reconstructed and wherein, in a bit-count control quantization loop following and de-linked from the quality control quantization loop, the encoder adjusts the quantization step size also in view of the target maximum-bits parameter, thereby reducing number of changes in quality and smoothing transitions between the changes in quality; and
entropy coding the quantized current block of information.
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Accused Products
Abstract
An audio encoder regulates quality and bitrate with a control strategy. The strategy includes several features. First, an encoder regulates quantization using quality, minimum bit count, and maximum bit count parameters. Second, an encoder regulates quantization using a noise measure that indicates reliability of a complexity measure. Third, an encoder normalizes a control parameter value according to block size for a variable-size block. Fourth, an encoder uses a bit-count control loop de-linked from a quality control loop. Fifth, an encoder addresses non-monotonicity of quality measurement as a function of quantization level when selecting a quantization level. Sixth, an encoder uses particular interpolation rules to find a quantization level in a quality or bit-count control loop. Seventh, an encoder filters a control parameter value to smooth quality. Eighth, an encoder corrects model bias by adjusting a control parameter value in view of current buffer fullness.
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Citations
19 Claims
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1. A computer-readable storage medium storing computer-executable instructions for causing a computer programmed thereby to perform a method of controlling quality of information in a constant bitrate encoder, wherein the encoder outputs the information at variable quality and compressed to a constant or relatively constant bitrate, the method comprising:
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determining a target maximum-bits parameter based at least in part upon (a) a first value constraining how many bits can be used in trying to satisfy a target quality parameter for a current block of information and (b) a second value indicating a number of bits available in a buffer until overflow; quantizing the current block of information to meet constant or relatively constant bitrate requirements, wherein, in a quality control quantization loop, the encoder adjusts quantization step size of the quantizing in view of a comparison of the target quality parameter for the current block to a quality measurement for the current block as quantized and reconstructed and wherein, in a bit-count control quantization loop following and de-linked from the quality control quantization loop, the encoder adjusts the quantization step size also in view of the target maximum-bits parameter, thereby reducing number of changes in quality and smoothing transitions between the changes in quality; and entropy coding the quantized current block of information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a spectral audio encoder, a computer-implemented method comprising:
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performing a frequency transform on plural time domain audio samples to produce a current block of frequency coefficients; and compressing the current block of frequency coefficients, wherein the compressing includes, determining a maximum-bits target based at least in part upon difference between (a) a first value constraining how many bits can be used in trying to satisfy a quality target and (b) a second value indicating a number of bits available in a buffer until overflow; quantizing the current block of frequency coefficients; comparing a quality measure for the current block to the quality target; and comparing a bit-count measure for the current block to a minimum-bits target and to the maximum-bits target. - View Dependent Claims (10)
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11. A computer-readable storage medium storing computer-executable instructions for causing computer programmed thereby to perform a method of controlling quality and bitrate in an audio encoder, the method comprising:
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determining one or more target quality parameters, a first target quality parameter of the one or more target quality parameters indicating an acceptable audio quality; determining plural target bitrate parameters, a first target bitrate parameter of the plural target bitrate parameters indicating a minimum acceptable number of bits produced, and a second target bitrate parameter of the plural target bitrate parameters indicating a maximum acceptable number of bits produced, wherein the determining the second target bitrate parameter is based at least in part upon (a) a first value constraining how many bits can be used in trying to satisfy the first target quality parameter and (b) a second value indicating a number of bits available in a buffer until overflow; and compressing current audio information, wherein quantization of the current audio information is based at least in part upon one or more comparisons of measures for the current audio information to the first target quality parameter, the first target bitrate parameter, and the second target bitrate parameter. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification