Efficient decomposition in noise and periodic signal waveforms in waveform interpolation

• US 5,924,061 A
• Filed: 03/10/1997
• Issued: 07/13/1999
• Est. Priority Date: 03/10/1997
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Shoham, Yair
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): SAX, ROBERT L
• Application Number:
  US08/813,183
• Time in Patent Office: 855 Days
• Field of Search: 704/218, 704/219, 704/203
• US Class Current: 704/218
• CPC Class Codes: G10L 19/097 using prototype waveform decomposition or prototype waveform interpolative [PWI] coders

Abstract

A low-complexity method and apparatus for performing signal decomposition in a low bit-rate WI speech encoder. A time-ordered sequence of sets of time-domain parameters is generated based on samples of a speech signal to be coded, each set of time-domain parameters corresponding to a waveform characterizing the speech signal. A cross correlation is then performed between two or more of said sets of time-domain parameters to produce a set of signals which represents relatively high rates of evolution of characterizing waveform shape across the time-ordered sequence of sets. Finally, the speech signal is coded based on the produced set of signals. A set of signals which represents relatively low rates of evolution of characterizing waveform shape across the time-ordered sequence of sets may also be produced. In this case, a time-ordered sequence of sets of frequency-domain parameters is also generated based on the samples of the speech signal to be coded, and an average of two or more of these sets of frequency-domain parameters is then computed. A set of signals which represents relatively low rates of evolution of characterizing waveform shape across the time-ordered sequence of sets is then produced based on the computed average, and the speech signal is then coded further based on this produced set of signals as well.

Claims

1. A method of coding a speech signal, the speech signal having a sequence of time-ordered short-term spectra corresponding thereto, the method comprising the steps of:

identifying a time-ordered sequence of speech signal segments;

generating a time-ordered sequence of sets of frequency-domain parameters based on samples of the speech signal;

performing a cross correlation between two or more of said speech signal segments to generate one or more parameters representing relatively high rates of evolution of said short-term spectra;

generating one or more sets of coefficients representing relatively low rates of evolution of said short-term spectra based on two or more of said sets of frequency-domain parameters; and

coding said speech signal based on the one or more generated parameters and further based on the one or more sets of coefficients representing relatively low rates of evolution of said short-term spectra.

2. The method of claim 1 wherein the step of coding the speech signal comprises selecting a codebook entry from a fixed codebook containing a plurality of codebook entries representing a corresponding plurality of magnitude spectra.

3. The method of claim 2 wherein each of the magnitude spectra in the codebook represents a magnitude difference of a first spectrum based on a first set of time-domain parameters and a second spectrum based on a second set of time-domain parameters.

4. The method of claim 2 wherein each of the codebook entries has an associated codebook index, and wherein the plurality of magnitude spectra are monotonically increasing with respect to the codebook indices associated therewith.

5. The method of claim 4 wherein the step of performing the cross correlation comprises generating one of said associated codebook indices, and wherein the step of coding the speech signal comprises selecting the codebook entry corresponding to the generated codebook index.

6. The method of claim 4 wherein the step of performing the cross correlation comprises generating a vector of soft index values, each soft index value corresponding to a magnitude spectrum, and wherein the step of coding the speech signal comprises performing a vector quantization on said vector of soft index values.

7. The method of claim 1 wherein each of the speech signal segments are substantially equal to a pitch-period in length.

8. The method of claim 1 wherein the speech signal comprises an LP residual signal.

9. The method of claim 1 wherein the step of generating the sets of frequency-domain parameters comprises performing a Fourier transform.

10. The method of claim 1 wherein the step of coding the speech signal comprises performing vector quantization on the one or more sets of coefficients representing relatively low rates of evolution of said short-term spectra.

11. An encoder for coding a speech signal, the speech signal having a sequence of time-ordered short-term spectra corresponding thereto, the encoder comprising:

means for identifying a time-ordered sequence of speech signal segments;

means for generating a time-ordered sequence of sets of frequency-domain parameters based on samples of the speech signal;

means for performing a cross correlation between two or more of said speech signal segments to generate one or more parameters representing relatively high rates of evolution of said short-term spectra;

means for generating one or more sets of coefficients representing relatively low rates of evolution of said short-term spectra based on two or more of said sets of frequency-domain parameters; and

means for coding said speech signal based on the one or more generated parameters and further based on the one or more sets of coefficients representing relatively low rates of evolution of said short-term spectra.

12. The encoder of claim 11 wherein the means for coding the speech signal comprises means for selecting a codebook entry from a fixed codebook containing a plurality of codebook entries representing a corresponding plurality of magnitude spectra.

13. The encoder of claim 12 wherein each of the magnitude spectra in the codebook represents a magnitude difference of a first spectrum based on a first set of time-domain parameters and a second spectrum based on a second set of time-domain parameters.

14. The encoder of claim 12 wherein each of the codebook entries has an associated codebook index, and wherein the plurality of magnitude spectra are monotonically increasing with respect to the codebook indices associated therewith.

15. The encoder of claim 14 wherein the means for performing the cross correlation comprises means for generating one of said associated codebook indices, and wherein the means for coding the speech signal comprises means for selecting the codebook entry corresponding to the generated codebook index.

16. The encoder of claim 14 wherein the means for performing the cross correlation comprises means for generating a vector of soft index values, each soft index value corresponding to a magnitude spectrum, and wherein the means for coding the speech signal comprises means for performing a vector quantization on said vector of soft index values.

17. The encoder of claim 11 wherein each of the speech signal segments are substantially equal to a pitch-period in length.

18. The encoder of claim 11 wherein the speech signal comprises an LP residual signal.

19. The encoder of claim 11 wherein the means for generating the sets of frequency-domain parameters comprises means for performing a Fourier transform.

20. The encoder of claim 11 wherein the means for coding the speech signal comprises means for performing vector quantization on the one or more sets of coefficients representing relatively low rates of evolution of said short term spectra.