Quantization loop with heuristic approach
First Claim
1. In a computer system with a spectral audio data encoder having an actual bit-rate feedback, uniform, scalar quantizer, a method for reducing the number of iterations of a quantization loop for a block of spectral audio data, the method comprising:
- a) setting a polynomial that relates actual bit-rate to quantization threshold for spectral audio data in an actual bit-rate feedback, uniform, scalar quantizer, the initial coefficients for the polynomial set for typical spectral audio data;
b) calculating a candidate quantization threshold for a block of spectral audio data based upon the polynomial;
c) quantizing the block of data with the candidate quantization threshold;
d) measuring bit-rate of output following compression of the quantized block;
e) if the measured bit-rate falls within a pre-determined range below a target bit-rate, designating the candidate quantization threshold as final quantization threshold;
else adjusting one or more coefficients of the polynomial and repeating b)-e).
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Abstract
A quantizer finds a quantization threshold using a quantization loop with a heuristic approach. Following the heuristic approach reduces the number of iterations in the quantization loop required to find an acceptable quantization threshold, which instantly improves the performance of an encoder system by eliminating costly compression operations. A heuristic model relates actual bit-rate of output following compression to quantization threshold for a block of a particular type of data. The quantizer determines an initial approximation for the quantization threshold based upon the heuristic model. The quantizer evaluates actual bit-rate following compression of output quantized by the initial approximation. If the actual bit-rate satisfies a criterion such as proximity to a target bit-rate, the quantizer sets accepts the initial approximation as the quantization threshold. Otherwise, the quantizer adjusts the heuristic model and repeats the process with a new approximation of the quantization threshold. In an illustrative example, a quantizer finds a uniform, scalar quantization threshold using a quantization loop with a heuristic model adapted to spectral audio data. During decoding, a dequantizer applies the quantization threshold to decompressed output in an inverse quantization operation.
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Citations
23 Claims
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1. In a computer system with a spectral audio data encoder having an actual bit-rate feedback, uniform, scalar quantizer, a method for reducing the number of iterations of a quantization loop for a block of spectral audio data, the method comprising:
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a) setting a polynomial that relates actual bit-rate to quantization threshold for spectral audio data in an actual bit-rate feedback, uniform, scalar quantizer, the initial coefficients for the polynomial set for typical spectral audio data;
b) calculating a candidate quantization threshold for a block of spectral audio data based upon the polynomial;
c) quantizing the block of data with the candidate quantization threshold;
d) measuring bit-rate of output following compression of the quantized block;
e) if the measured bit-rate falls within a pre-determined range below a target bit-rate, designating the candidate quantization threshold as final quantization threshold;
else adjusting one or more coefficients of the polynomial and repeating b)-e).
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2. A computer-readable medium storing instructions for a method of reducing the number of iterations of a quantization loop, the method comprising:
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a) setting a model that relates actual bit-rate to uniform, scalar quantization threshold for a data type in an actual bit-rate feedback quantizer;
b) calculating a candidate uniform, scalar quantization threshold for a block of input data based upon the model;
c) quantizing the block of input data with the candidate quantization threshold;
d) measuring bit-rate of output following compression of the quantized block;
e) if the measured bit-rate is acceptable, designating the candidate quantization threshold as final quantization threshold for the block of input data;
else adjusting the model and repeating b)-e). - View Dependent Claims (3, 4, 5, 6, 7)
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8. In a computer system with an encoder having a quantizer, a method for finding a quantization threshold using a quantization loop with a heuristic approach, the method comprising:
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estimating a quantization threshold based upon a heuristic model of actual bit-rate versus quantization threshold, wherein the model adjusts responsive to negative evaluation of an acceptability criterion for the estimated quantization threshold;
evaluating whether bit-rate of compressed output quantized by the estimated quantization threshold satisfies the acceptability criterion and if so, designating the estimated quantization threshold as final quantization threshold, and if not, adjusting the model and repeating the estimating and evaluating. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21)
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17. In a computer system, a bit-rate feedback quantizer comprising:
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a threshold estimator for estimating a quantization threshold based upon a model of actual bit-rate versus quantization threshold, wherein the threshold estimator adjusts the model responsive to a negative evaluation of an acceptability criterion for the quantization threshold;
a threshold evaluator for evaluating actual bit-rate of output following compression, the threshold evaluator further evaluating whether the estimated quantization threshold satisfies the acceptability criterion.
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22. A computer-readable medium storing instructions for a bit-rate feedback quantizer with a heuristic approach, the quantizer comprising:
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means for estimating a quantization threshold based upon a heuristic model of actual bit-rate as a function of quantization threshold, wherein the means for estimating adjusts one or more parameters of the model responsive to a negative evaluation of acceptability of the estimated quantization threshold;
means for evaluating actual bit-rate following compression of output quantized by the estimated quantization threshold, wherein the means for evaluating further evaluates the acceptability of the estimated quantization threshold.
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23. A computer-readable medium storing instructions for a method of dequantizing a block of input data quantized in a bit-rate feedback quantizer with a heuristic approach, the method comprising:
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receiving a block of quantized input data, the input data quantized by a bit-rate feedback quantizer with a heuristic approach;
the quantizer including a threshold estimator and a threshold evaluator, the threshold estimator for estimating a quantization threshold based upon a heuristic model of actual bit-rate versus quantization threshold, wherein the threshold estimator adjusts the model responsive to a negative evaluation of an acceptability criterion for the estimated quantization threshold, the threshold evaluator for evaluating actual bit-rate following compression of output quantized by the estimated quantization threshold, wherein the threshold evaluator further evaluates whether the estimated quantization threshold satisfies the acceptability criterion; and
applying the final quantization threshold to the block of quantized input data in inverse quantization.
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Specification