Adaptive postfiltering methods and systems for decoding speech
First Claim
1. A method of processing a decoded speech (DS) signal comprising:
- (a) filtering the DS signal using a first intermediate set of filter coefficients to generate a first intermediate spectrally-flattened DS signal,(b) deriving a second intermediate set of filter coefficients from the first intermediate spectrally-flattened DS signal,(c) filtering the first intermediate spectrally-flattened DS signal using the second intermediate set of filter coefficients to generate a second intermediate spectrally-flattened DS signal, and(d) deriving a set of filter coefficients from the second intermediate spectrally-flattened DS signal.
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Abstract
A filter controller processes a decoded speech (DS) signal. The DS signal has a spectral envelope including a first plurality of formant peaks having different respective amplitudes. The controller produces, from the DS signal, a spectrally-flattened DS signal that is a time-domain signal. The spectrally-flattened time-domain DS signal has a spectral envelope including a second plurality of formant peaks. Each of the second plurality of formant peaks approximately coincides in frequency with a respective one of the first plurality of formant peaks. Also, the second plurality of formant peaks have approximately equal respective amplitudes. Next, the controller derives, from the spectrally-flattened time-domain DS signal, a set of filter coefficients representative of a filter response that is to be used to filter the DS signal.
48 Citations
30 Claims
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1. A method of processing a decoded speech (DS) signal comprising:
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(a) filtering the DS signal using a first intermediate set of filter coefficients to generate a first intermediate spectrally-flattened DS signal, (b) deriving a second intermediate set of filter coefficients from the first intermediate spectrally-flattened DS signal, (c) filtering the first intermediate spectrally-flattened DS signal using the second intermediate set of filter coefficients to generate a second intermediate spectrally-flattened DS signal, and (d) deriving a set of filter coefficients from the second intermediate spectrally-flattened DS signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of processing a decoded speech (DS) signal, the DS signal having a spectral envelope including a plurality of DS formant peaks having different respective amplitudes, comprising:
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(a) deriving a first set of filter coefficients based on the DS signal; (b) filtering the DS signal based on the first set of filter coefficients;
to produce a first filtered DS signal;(c) deriving a second set of filter coefficients based on the first filtered DS signal; (d) filtering the first filtered DS signal based on the second set of filter coefficients to produce a second filtered DS signal, the second filtered DS signal having a spectral envelope including a plurality of second formant peaks corresponding to the plurality of DS formant peaks, the plurality of second formant peaks having approximately equal amplitudes; and (e) deriving a final set of filter coefficients from the second filtered DS signal. - View Dependent Claims (17, 18)
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19. A computer program product (CPP) comprising a computer usable storage medium having computer readable program code (ORPO) means embodied in the medium for causing an application program to execute on a computer processor to perform processing of a decoded speech (DS) signal by a method comprising:
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filtering the DS signal using a first intermediate set of filter coefficients to generate a first intermediate spectrally-flattened DS signal, deriving a second intermediate set of filter coefficients from the first intermediate spectrally-flattened DS signal, filtering the first intermediate spectrally-flattened DS signal using the second intermediate set of filter coefficients to generate a second intermediate spectrally-flattened DS signal, and deriving a set of filter coefficients from the second intermediate spectrally-flattened DS signal. - View Dependent Claims (20, 21, 22, 23)
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24. An apparatus for processing a decoded speech (DS) signal, comprising:
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first means for producing, from the DS signal and a first intermediate set of filter coefficients, a first spectrally-flattened DS signal, second means for deriving a second intermediate set of filter coefficients from the first spectrally-flattened time-domain DS signal, third means for filtering the first intermediate spectrally-flattened DS signal using the second intermediate set of filter coefficients to generate a second intermediate spectrally-flattened DS signal, and fourth means for deriving a set of filter coefficients from the second intermediate spectrally-flattened DS signal. - View Dependent Claims (25, 26)
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27. An apparatus for processing a decoded speech signal, the DS signal including a plurality of formant peaks, comprising:
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a filter controller including a first controller stage configured to produce, from the DS signal and a first intermediate set of filter coefficients, a first intermediate spectrally-flattened DS signal, a second controller stage confignred to derive a second intermediate set of filter coefficients from the first intermediate spectrally-flattened time-domain DS signal, a third controller stage configured to derive a second intermediate spectrally-flattened DS signal from the first intermediate spectrally-flattened DS signal and the second intermediate set of filter coefficients to generate, and a fourth controller stage configured to derive a set of filter coefficients from the second intermediate spectrally-flattened DS signal. - View Dependent Claims (28, 29, 30)
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Specification