Prototype waveform magnitude quantization for a frequency domain interpolative speech codec system
First Claim
1. A frequency domain interpolative CODEC system for low bit rate coding of speech, comprising:
- a linear prediction (LP) front end adapted to process an input signal providing LP parameters which are quantized and encoded over predetermined intervals and used to compute a LP residual signal;
an open loop pitch estimator adapted to process said LP residual signal, a pitch quantizer, and a pitch interpolator and provide a pitch contour within the predetermined intervals; and
a signal processor responsive to said LP residual signal and the pitch contour and adapted to perform the following steps;
extract a prototype waveform (PW) from the LP residual and the open loop pitch contour for a number of equal sub-intervals within the predetermined intervals;
normalize the PW by said PW'"'"'s gain;
represent a variable dimension PW in a magnitude domain without further decomposition of said PW into complex components in a mean plus deviations form in multiple bands;
compute a voicing measure, said voicing measure characterizing a degree of voicing of said input speech signal and is derived from several input parameters that are correlated to degrees of periodicity of the signal over the predetermined intervals;
provide for a voicing classification for the predetermined intervals based on the computed voicing measure; and
quantize the PW multi-band mean plus deviations for all speech frames in a magnitude domain using a hierarchical quantization method that employs fixed dimension vector quantizers (VQ) with parameters based on the voicing classification.
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Abstract
A system and method is provided that employs a frequency domain interpolative CODEC system for low bit rate coding of speech which comprises a linear prediction (LP) front end adapted to process an input signal that provides LP parameters which are quantized and encoded over predetermined intervals and used to compute a LP residual signal. An open loop pitch estimator adapted to process the LP residual signal, a pitch quantizer, and a pitch interpolator and provide a pitch contour within the predetermined intervals is also provided. Also provided is a signal processor responsive to the LP residual signal and the pitch contour and adapted to perform the following: provide a voicing measure, where the voicing measure characterizes a degree of voicing of the input speech signal and is derived from several input parameters that are correlated to degrees of periodicity of the signal over the predetermined intervals; extract a prototype waveform (PW) from the LP residual and the open loop pitch contour for a number of equal sub-intervals within the predetermined intervals; normalize the PW by a gain value of the PW; encode a magnitude of the PW; and directly quantize the PW in a magnitude domain without further decomposition of the PW into complex components, where the direct quantization is performed by a hierarchical quantization method based on a voicing classification using fixed dimension vector quantizers (VQ'"'"'s).
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Citations
8 Claims
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1. A frequency domain interpolative CODEC system for low bit rate coding of speech, comprising:
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a linear prediction (LP) front end adapted to process an input signal providing LP parameters which are quantized and encoded over predetermined intervals and used to compute a LP residual signal; an open loop pitch estimator adapted to process said LP residual signal, a pitch quantizer, and a pitch interpolator and provide a pitch contour within the predetermined intervals; and a signal processor responsive to said LP residual signal and the pitch contour and adapted to perform the following steps; extract a prototype waveform (PW) from the LP residual and the open loop pitch contour for a number of equal sub-intervals within the predetermined intervals; normalize the PW by said PW'"'"'s gain; represent a variable dimension PW in a magnitude domain without further decomposition of said PW into complex components in a mean plus deviations form in multiple bands; compute a voicing measure, said voicing measure characterizing a degree of voicing of said input speech signal and is derived from several input parameters that are correlated to degrees of periodicity of the signal over the predetermined intervals; provide for a voicing classification for the predetermined intervals based on the computed voicing measure; and quantize the PW multi-band mean plus deviations for all speech frames in a magnitude domain using a hierarchical quantization method that employs fixed dimension vector quantizers (VQ) with parameters based on the voicing classification. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification