Audio coding system using spectral hole filling
First Claim
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1. A method for generating audio information, wherein the method comprises:
- receiving an input signal and obtaining therefrom a set of subband signals each having one or more spectral components representing spectral content of an audio signal;
identifying within the set of subband signals a particular subband signal in which one or more spectral components have a non-zero value and in which one or more of the spectral components have a zero value;
deriving a scaling envelope from the one or more spectral components that have non-zero values, wherein the scaling envelope varies at a rate substantially equal to a rate of roll off of spectral leakage between adjacent subband signals of a synthesis filterbank;
generating one or more synthesized spectral components that correspond to zero-valued spectral components in the particular subband signal and that are scaled according to the scaling envelope;
generating a modified set of subband signals by substituting the synthesized spectral components for corresponding zero-valued spectral components in the particular subband signal; and
generating the audio information by applying the synthesis filterbank to the modified set of subband signals.
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Abstract
Audio coding processes like quantization can cause spectral components of an encoded audio signal to be set to zero, creating spectral holes in the signal. These spectral holes can degrade the perceived quality of audio signals that are reproduced by audio coding systems. An improved decoder avoids or reduces the degradation by filling the spectral holes with synthesized spectral components. An improved encoder may also be used to realize further improvements in the decoder.
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Citations
24 Claims
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1. A method for generating audio information, wherein the method comprises:
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receiving an input signal and obtaining therefrom a set of subband signals each having one or more spectral components representing spectral content of an audio signal; identifying within the set of subband signals a particular subband signal in which one or more spectral components have a non-zero value and in which one or more of the spectral components have a zero value; deriving a scaling envelope from the one or more spectral components that have non-zero values, wherein the scaling envelope varies at a rate substantially equal to a rate of roll off of spectral leakage between adjacent subband signals of a synthesis filterbank; generating one or more synthesized spectral components that correspond to zero-valued spectral components in the particular subband signal and that are scaled according to the scaling envelope; generating a modified set of subband signals by substituting the synthesized spectral components for corresponding zero-valued spectral components in the particular subband signal; and generating the audio information by applying the synthesis filterbank to the modified set of subband signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for generating audio information, wherein the apparatus comprises:
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a deformatter that receives an input signal and obtains therefrom a sec of subband signals each having one or more spectral components representing spectral content of an audio signal; a decoder coupled to the deformatter that identifies within the set of subband signals a particular subband signal in which one or more spectral components have a non-zero value and in which one or more of the spectral components have a zero value, that derives a scaling envelope from the one or more spectral components that have non-zero values, wherein the scaling envelope varies at a rate substantially equal to a rate of roll off of spectral leakage between adjacent subband signals of a synthesis filterbank, that generates one or more synthesized spectral components that correspond to zero-valued spectral components in the particular subband signal and are scaled according to the scaling envelope, and that generates a modified set of subband signals by substituting the synthesized spectral components for corresponding zero-valued spectral components in the particular subband signal; and the synthesis filterbank coupled to the decoder that generates the audio information in response to the modified set of subband signals. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A computer-readable storage medium recording a program of instructions that is readable by a processor for executing the program of instructions to perform a method for generating audio information, wherein the method comprises:
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receiving an input signal and obtaining therefrom a set of subband signals each having one or more spectral components representing spectral content of an audio signal; identifying within the set of subband signals a particular subband signal in which one or more spectral components have a non-zero value and in which one or more of the spectral components have a zero value; deriving a scaling envelope from the one or more spectral components that have non-zero values, wherein the scaling envelope varies at a rate substantially equal to a rate roll off of spectral leakage between adjacent subband signals of a synthesis filterbank; generating one or more synthesized spectral components that correspond to zero-valued spectral components in the particular subband signal and that are scaled according to the scaling envelope; generating a modified set of subband signals by substituting the synthesized spectral components for corresponding zero-valued spectral components in the particular subband signal; and generating the audio information by applying the synthesis filterbank to the modified set of subband signals. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification