Speech encoding device
AssigneeInterDigital Technology Corporation
InventorsDaniel Lin, Brian McCarthy
Life of this patent
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Abstract
The present invention is a synthetic speech encoding device that produces a synthetic speech signal which closely matches an actual speech signal. The actual speech signal is digitized, and excitation pulses are selected by minimizing the error between the actual and synthetic speech signals. The preferred pattern of excitation pulses needed to produce the synthetic speech signal is obtained by using an excitation pattern containing a multiplicity of weighted pulses at timed positions. The selection of the location and amplitude of each excitation pulse is obtained by minimizing an error criterion between the synthetic speech signal and the actual speech signal. The error criterion function incorporates a perceptual weighting filter which shapes the error spectrum.
Claims4
A synthetic speech encoding device comprising:
- sample and hold circuitry and an analog to digital converter for digitizing an actual speech signal and partitioning the digitized signal into a selected number of blocks;
- a pre-emphasis filter for pre-emphasizing the blocks;
- a linear predictive coding (LPC) device for producing LPC reflection coefficients from the pre-emphasized samples;
- a quantizing device for quantizing the reflection coefficients based on voiced and unvoiced speech;
- a spectral converter for converting the quantized reflection coefficients to spectral coefficients;
- an interpolator for interpolating the spectral coefficients;
- and
- a pitch analyzer for subjecting the interpolated spectral coefficients to pitch analysis to obtain a spectral residual signal, so that the actual speech signal is encoded into a synthetic speech signal.
A synthetic speech encoding device comprising:
- sample and hold circuitry and an analog to digital converter for digitizing an actual speech signal and partitioning the digitized signal into a selected number of blocks;
- a pre-emphasis filter for pre-emphasizing the blocks;
- a linear predictive coding (LPC) device for producing LPC reflection coefficients from the pre-emphasized samples;
- a quantizing device for quantizing the reflection coefficients into a first set of bits by using a set of quantizer tables based on voiced speech, and a second set of bits by using a set of quantizer tables based on unvoiced speech;
- a spectral converter for converting the quantized reflection coefficients to spectral coefficients;
- a processor for computing the log-spectral distance between an unquantized spectrum of the reflection coefficients and each quantized spectrum of the first and second sets of bits;
- a memory for retaining the set of quantized bits which produces the smaller log-spectral distance;
- and
- a coefficient converter for converting the retained bits to LPC filter coefficients;
- so that the actual speech signal is encoded into a synthetic speech signal.
Dependencies are inferred from the claim text.