System and method for performing pitch estimation and error checking on low estimated pitch values in a correlation based pitch estimator
First Claim
1. A method for performing pitch error checking in a correlation-based pitch estimator, comprising:
- receiving a speech waveform comprising a plurality of frames;
performing a correlation calculation for a first frame of said plurality of frames of said speech waveform, wherein said correlation calculation produces one or more correlation peaks;
determining a first determined pitch value for said first frame from said one or more correlation peaks, wherein said first determined pitch value corresponds to a first determined correlation peak;
determining if said first determined pitch value is less than a pitch threshold value;
setting said first determined pitch value as a pitch value for said first frame if said first determined pitch value is not less than said pitch threshold value;
performing error checking on said first determined pitch value to determine if said first determined pitch value should be set as the pitch value for said first frame if said first determined pitch value is less than said pitch threshold value, wherein said performing error checking includes determining if any pitch multiples of said first determined pitch value have missing correlation peaks; and
determining a new determined pitch value for said first frame from at least a subset of said one or more correlation peaks, wherein said determining said new determined pitch value does not use said first determined correlation peak, wherein said determining said new determined pitch value is performed if any pitch multiples of said first determined pitch value have missing correlation peaks.
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Abstract
An improved vocoder system and method for estimating pitch in a speech waveform which more accurately disregards false pitch estimates resulting from secondary excitations. The vocoder system first performs a correlation calculation on a speech frame and generates an estimated pitch value. The present invention then compares the estimated or determined pitch with a threshold value to determine if the determined or estimated pitch has a suspiciously low pitch value. If so, the present invention performs error checking to disregard pitch estimates that are the result of the First Formant frequency'"'"'s contribution to the pitch estimation process. The error checking involves examining the higher multiples of the determined pitch value to ascertain whether the determined pitch value might be incorrect. The present invention determines whether one or more higher multiples are missing, whether the higher multiples are related by a common factor, and whether adjacent multiples have missing peaks. The error checking also involves searching for missing or low correlation peaks in the neighborhood of missing higher multiples of the determined pitch. If the error checking indicates that the determined pitch is probably incorrect, then a new determination is made without the correlation peak corresponding to the rejected determined pitch. This provides a more accurate pitch estimation, thus enhancing voice storage quality. The present invention thus comprises an improved correlation method for estimating the pitch parameter which more accurately disregards false correlation peaks resulting from secondary excitations, including the contribution of the First Formant.
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Citations
19 Claims
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1. A method for performing pitch error checking in a correlation-based pitch estimator, comprising:
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receiving a speech waveform comprising a plurality of frames; performing a correlation calculation for a first frame of said plurality of frames of said speech waveform, wherein said correlation calculation produces one or more correlation peaks; determining a first determined pitch value for said first frame from said one or more correlation peaks, wherein said first determined pitch value corresponds to a first determined correlation peak; determining if said first determined pitch value is less than a pitch threshold value; setting said first determined pitch value as a pitch value for said first frame if said first determined pitch value is not less than said pitch threshold value; performing error checking on said first determined pitch value to determine if said first determined pitch value should be set as the pitch value for said first frame if said first determined pitch value is less than said pitch threshold value, wherein said performing error checking includes determining if any pitch multiples of said first determined pitch value have missing correlation peaks; and determining a new determined pitch value for said first frame from at least a subset of said one or more correlation peaks, wherein said determining said new determined pitch value does not use said first determined correlation peak, wherein said determining said new determined pitch value is performed if any pitch multiples of said first determined pitch value have missing correlation peaks. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for performing pitch error checking in a correlation-based pitch estimator, comprising:
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receiving a speech waveform comprising a plurality of frames; performing a correlation calculation for a first frame of said plurality of frames of said speech waveform, wherein said correlation calculation produces one or more correlation peaks; determining a first determined pitch value for said first frame from said one or more correlation peaks, wherein said first determined pitch value corresponds to a determined correlation peak; determining if said first determined pitch value is less than a pitch threshold value; setting said first determined pitch value as a pitch value for said first frame if said first determined pitch value is not less than said pitch threshold value; performing error checking on said first determined pitch value to determine if said first determined pitch value should be set to the pitch value of said first frame if said first determined pitch value is less than said pitch threshold value, wherein said performing error checking comprises; determining if said correlation peaks other than said determined correlation peak have a common factor; and determining if any pitch multiples of said first determined pitch value have missing correlation peaks if said peaks other than said determined correlation peak have a common factor; and determining a new determined pitch value for said first frame from a subset of said one or more correlation peaks, wherein said determining said new determined pitch value does not use said determined correlation peak, wherein said determining said new determined pitch value is performed if said correlation peaks other than said determined correlation peak have a common factor and if any pitch multiples of said first determined pitch value have missing correlation peaks.
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13. A method for performing pitch error checking in a correlation-based pitch estimator, comprising:
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receiving a speech waveform comprising a plurality of frames; performing a correlation calculation for a first frame of said plurality of frames of said speech waveform, wherein said correlation calculation produces one or more correlation peaks; determining a first determined pitch value for said first frame from said one or more correlation peaks, wherein said first determined pitch value corresponds to a first determined correlation peak; determining if said first determined pitch value is less than a pitch threshold value; setting said first determined pitch value as a pitch value for said first frame if said first determined pitch value is not less than said pitch threshold value; performing error checking on said first determined pitch value to determine if said first determined pitch value should be set as the pitch value for said first frame if said first determined pitch value is less than said pitch threshold value, wherein said performing error checking includes analyzing pitch multiples of said first determined pitch value; and determining a new determined pitch value for said first frame from at least a subset of said one or more correlation peaks if said analyzing said pitch multiples of said first determined pitch value indicates that said first determined pitch value may not be the correct pitch value of said first frame. - View Dependent Claims (14, 15, 16)
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17. A vocoder which performs pitch estimation and error checking, comprising:
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means for receiving a plurality of digital samples of a speech waveform, wherein the speech waveform includes a plurality of frames each comprising a plurality of samples; a processor for determining a pitch value for each of said frames, wherein said processor comprises; means for performing a correlation calculation for a first frame of said plurality of frames of said speech waveform, wherein said correlation calculation produces one or more correlation peaks; means for determining a first determined pitch value for said first frame from said one or more correlation peaks, wherein said first determined pitch value corresponds to a first determined correlation peak; means for determining if said first determined pitch value is less than a pitch threshold value; means for setting said first determined pitch value as a pitch value for said first frame if said first determined pitch value is not less than said pitch threshold value; means for performing error checking on said first determined pitch value to determine if said first determined pitch value should be set as the pitch value for said first frame if said first determined pitch value is less than said pitch threshold value, wherein said means for performing error checking determines if any pitch multiples of said first determined pitch value have missing correlation peaks; and means for determining a new determined pitch value for said first frame from at least a subset of said one or more correlation peaks, wherein said means for determining a new determined pitch value does not use said first determined correlation peak, wherein said means for determining a new determined pitch value operates if any pitch multiples of said first determined pitch value have missing correlation peaks. - View Dependent Claims (18, 19)
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Specification