Audio codec post-filter
First Claim
Patent Images
1. A computer-implemented method comprising:
- calculating a set of filter coefficients for application to a reconstructed audio signal, wherein the calculating the set of filter coefficients comprises;
performing a transform of a set of initial time domain values from a time domain into a frequency domain, thereby producing a set of initial frequency domain values;
performing one or more frequency domain calculations using the initial frequency domain values to produce a set of processed frequency domain values; and
performing a transform of the processed frequency domain values from the frequency domain into the time domain, thereby producing a set of processed time domain values; and
producing a filtered audio signal by filtering at least a portion of the reconstructed audio signal in a time domain using the set of filter coefficients; and
wherein performing one or more frequency domain calculations using the initial frequency domain values to produce a set of processed frequency domain values comprises clipping frequency domain values in the frequency domain such that only those frequency domain values which exceed a maximum clip value are clipped.
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Abstract
Techniques and tools are described for processing reconstructed audio signals. For example, a reconstructed audio signal is filtered in the time domain using filter coefficients that are calculated, at least in part, in the frequency domain. As another example, producing a set of filter coefficients for filtering a reconstructed audio signal includes clipping one or more peaks of a set of coefficient values. As yet another example, for a sub-band codec, in a frequency region near an intersection between two sub-bands, a reconstructed composite signal is enhanced.
149 Citations
31 Claims
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1. A computer-implemented method comprising:
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calculating a set of filter coefficients for application to a reconstructed audio signal, wherein the calculating the set of filter coefficients comprises; performing a transform of a set of initial time domain values from a time domain into a frequency domain, thereby producing a set of initial frequency domain values; performing one or more frequency domain calculations using the initial frequency domain values to produce a set of processed frequency domain values; and performing a transform of the processed frequency domain values from the frequency domain into the time domain, thereby producing a set of processed time domain values; and producing a filtered audio signal by filtering at least a portion of the reconstructed audio signal in a time domain using the set of filter coefficients; and wherein performing one or more frequency domain calculations using the initial frequency domain values to produce a set of processed frequency domain values comprises clipping frequency domain values in the frequency domain such that only those frequency domain values which exceed a maximum clip value are clipped. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method comprising:
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producing a set of filter coefficients for application to a reconstructed audio signal, including processing a set of values in a frequency domain representing one or more peaks and one or more valleys, wherein the processing the set of values in the frequency domain comprises clipping one or more of the peaks or valleys, and wherein the clipping includes capping the set of values in the frequency domain at a maximum clip value by setting values which exceed the maximum clip value to the clip value and maintaining the values which do not exceed the maximum clip value; and filtering at least a portion of the reconstructed audio signal using the filter coefficients. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A computer-implemented method comprising:
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receiving a reconstructed composite signal synthesized from plural reconstructed frequency sub-band signals, the plural reconstructed frequency sub-band signals including a reconstructed first frequency sub-band signal for a first frequency band and a reconstructed second frequency sub-band signal for a second frequency band; and selectively enhancing the reconstructed composite signal at a frequency region around an intersection between the first frequency band and the second frequency band, wherein enhancing the reconstructed composite signal comprises passing the reconstructed composite signal through a baud pass filter, wherein a pass band of the band pass filter corresponds to the frequency region around the intersection between the first frequency band and the second frequency band. - View Dependent Claims (24, 25, 26, 27)
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28. A method comprising:
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producing a set of filter coefficients for application to a reconstructed audio signal, including processing a set of coefficient values representing one or more peaks and one or more valleys, wherein the processing the set of coefficient values comprises clipping one or more of the peaks or valleys such that only those coefficient values which exceed a maximum clip value are clipped, and wherein the set of coefficient values is based at least in part on a set of linear prediction coefficient values; and filtering at least a portion of the reconstructed audio signal using the filter coefficients.
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29. A method comprising:
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producing a set of filter coefficients for application to a reconstructed audio signal, including processing a set of coefficient values representing one or more peaks and one or more valleys, wherein the processing the set of coefficient values comprises clipping one or more of the peaks or valleys such that only those coefficient values which exceed a maximum clip value are clipped, and wherein the clipping is performed in a frequency domain; and filtering at least a portion of the reconstructed audio signal using the filter coefficients.
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30. A method comprising:
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producing a set of filter coefficients for application to a reconstructed audio signal, including processing a set of coefficient values representing one or more peaks and one or more valleys, wherein the processing the set of coefficient values comprises clipping one or more of the peaks or valleys such that only those coefficient values which exceed a maximum clip value are clipped; and filtering at least a portion of the reconstructed audio signal using the filter coefficients, wherein the filtering is performed in a time domain.
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31. A method comprising:
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producing a set of filter coefficients for application to a reconstructed audio signal, including processing a set of coefficient values representing one or more peaks and one or more valleys, wherein the processing the set of coefficient values comprises; reducing a range of the set of coefficient values; and clipping one or more of the peaks or valleys such that only those coefficient values which exceed a maximum clip value are clipped; and filtering at least a portion of the reconstructed audio signal using the filter coefficients.
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Specification