US 7,406,412 B2Granted

Reduced computational complexity of bit allocation for perceptual coding

AssigneeDolby Laboratories Licensing Corporation

InventorsStephen Decker Vernon, Charles Quito Robinson, Robert Loring Andersen

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Abstract

A process that allocates bits for quantizing spectral components in a perceptual coding system is performed more efficiently by obtaining an accurate estimate of the optimal value for one or more coding parameters that are used in the bit allocation process. In one implementation for a perceptual audio coding system, an accurate estimate of an offset from a calculated psychoacoustic masking curve is derived by selecting an initial value for the offset, calculating the number of bits that would be allocated if the initial offset were used for coding, and estimating the optimum value of the offset from a difference between this calculated number and the number of bits that are actually available for allocation.

Claims6

Dependent claims

A method for encoding an audio signal that comprises:

receiving spectral components that represent spectral content of the audio signal;
applying a perceptual model to the spectral components to obtain a first masking curve that represents perceptual masking effects of the audio signal;
deriving an estimated value of a coding parameter that specifies an offset between a second masking curve and the first masking curve, wherein the estimated value of the coding parameter is derived in response to a number of bits that are available for encoding the audio signal, and wherein the deriving of the estimated value of the coding parameter comprises:
selecting an initial value for the coding parameter;
determining a first number of bits in response to the initial value of the coding parameter to use in quantizing the spectral components;
determining a second number of bits from a difference between the first number of bits and a third number of bits, wherein the third number of bits corresponds to the number of bits that are available for encoding the audio signal;
and
deriving the estimated value of the coding parameter in response to the initial value of the coding parameter and the second number of bits;
obtaining an optimum value of the coding parameter by modifying the estimated value of the coding parameter in an iterative process that searches for the optimum value of the coding parameter according to the perceptual model;
generating encoded spectral components by quantizing spectral components according to the second masking curve, wherein resolution of the quantizing is responsive to the first masking curve and the coding parameter such that the optimum value of the coding parameter minimizes perceptibilty of quantizing noise according to the perceptual model;
and
assembling a representation of the encoded spectral components into an output signal.

9 more elements

An apparatus for encoding an audio signal that comprises:

(a) an input terminal;
(b) an output terminal;
and
(c) signal processing circuitry coupled to the input terminal and the output terminal, wherein the signal processing circuitry is adapted to:
receive a signal from the input terminal and obtain thereform spectral components that represent spectral content of the audio signal;
apply a perceptual model to the spectral components to obtain a first masking curve that represents perceptual masking effects of the audio signal;
derive an estimated value of a coding parameter that specifies an offset between a second masking curve and the first masking curve, wherein the estimated value of the coding parameter is derived in response to a number of bits that are available for encoding the audio signal, wherein derivation of the estimated value of the coding parameter comprises:
selecting an initial value for the coding parameter;
determining a first number of bits in response to the initial value of the coding parameter to use in quantizing the spectral components;
determining a second number of bits from a difference between the first number of bits and a third number of bits, wherein the third number of bits corresponds to the number of bits that are available for encoding the audio signal;
and
deriving the estimated value of the coding parameter in response to the initial value of the coding parameter and the second number of bits;
obtain an optimum value of the coding parameter by modifying the estimated value of the coding parameter in an iterative process that searches for the optimum value of the coding parameter according to the perceptual model;
generate encoded spectral components by quantizing spectral components according to the second masking curve, wherein resolution of the quantizing is responsive to the first masking curve and the coding parameter such that the optimum value of the coding parameter minimizes perceptibilty of quantizing noise according to the perceptual model;
and
assemble a representation of the encoded spectral components into an output signal that is sent to the output terminal.

13 more elements

Dependencies are inferred from the claim text.