Method and apparatus for generating a candidate code-vector to code an informational signal

• US 9,070,356 B2
• Filed: 04/04/2012
• Issued: 06/30/2015
• Est. Priority Date: 04/04/2012
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Inventors: Ashley, James P., Mittal, Udar
• Primary Examiner(s): Chawan, Vijay B
• Application Number:
  US13/439,121
• Publication Number:
  US 20130268266A1
• Time in Patent Office: 1,182 Days
• Field of Search: 704/223, 704/219, 704/222, 704/220, 704/264, 704/229, 704/216, 704/218, 704/226, 704/230, 704/225, 704/207
• US Class Current: 1/1
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/083 the excitation function being an excitation gain G10L25/90 takes precedence
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 2019/0013 Codebook search algorithms

Abstract

A method (300) and apparatus (100) generate a candidate code-vector to code an information signal. The method can include producing (310) a target vector from a received input signal. The method can include constructing (320) a plurality of inverse weighting functions based on the target vector. The method can include evaluating (330) an error value associated with each of the plurality of inverse weighting functions to produce a fixed codebook code-vector. The method can include generating (340) a codeword representative of the fixed codebook code-vector, where the codeword can be used by a decoder to generate an approximation of the input signal.

Claims

1. A method comprising:

receiving an input signal;

producing a target vector from the input signal;

constructing a plurality of candidate code-vectors based on the target vector and based on at least one inverse weighting function;

evaluating an error value associated with each code-vector of the plurality of candidate code-vectors to produce a fixed codebook code-vector; and

generating a codeword representative of the fixed codebook code-vector, where the codeword is for use by a decoder to generate an approximation of the input signal.

2. The method according to claim 1, wherein the method further comprises:

outputting the codeword by one of;

transmitting the codeword and storing the codeword.

3. The method according to claim 1, wherein the at least one inverse weighting function is based on an inverse filtered vector constructed from the target vector.

4. The method according to claim 3,

wherein the inverse filtered vector is constructed based on r=H⁻

1x₂,

wherein r comprises the inverse filtered vector,

wherein H<sup>−

1</sup> comprises a zero-state weighted synthesis convolution matrix formed from an impulse response of a weighted synthesis filter, and

wherein x₂ comprises the target vector.

5. The method according to claim 1, wherein the at least one inverse weighting function is based on a backward filtered vector constructed from the target vector.

6. The method according to claim 5,

wherein the backward filtered vector is constructed based on d₂=H^Tx₂,

wherein d₂ comprises the backward filtered vector,

wherein H^T comprises a transpose of a zero-state weighted synthesis convolution matrix formed from an impulse response of a weighted synthesis filter, and

wherein x₂ comprises the target vector.

7. The method according to claim 1, wherein the constructing comprises:

constructing the plurality of inverse weighting functions based on the target vector, based on an inverse filtered vector, and based on a backward filtered vector.

8. The method according to claim 1, wherein the constructing comprises:

constructing the plurality of inverse weighting functions based on the target vector and based on a sum of a weighted inverse filtered vector and a weighted backward filtered vector.

9. The method according to claim 1, wherein the plurality of candidate code-vectors are based on one of:

an inverse filtered vector constructed from the target vector and a backward filtered vector constructed from the target vector.

10. The method according to claim 9, further comprising:

processing each of the plurality of candidate code-vectors using a fixed codebook and through a zero state weighted synthesis filter a plurality of times,

wherein the evaluating comprises;

evaluating at least one error value associated with each iteration of the plurality of candidate code-vectors from the plurality of times to produce the fixed codebook code-vector based on the candidate code-vector with a lowest error value.

11. An apparatus comprising:

an input configured to receive an input signal;

a target vector generator configured to produce a target vector from the input signal;

a fixed codebook candidate code-vector generator configured to construct a plurality of candidate code-vectors based on the target vector and based on at least one inverse weighting function;

an error minimization unit configured to evaluate an error value associated with each code-vector of the plurality of candidate code-vectors to produce a fixed codebook code-vector; and

an output configured to output a codeword based on the fixed codebook code-vector.

12. The apparatus according to claim 11, further comprising:

wherein the output is configured to output the codeword by one of transmitting the codeword and storing the codeword.

13. The apparatus according to claim 11, wherein the fixed codebook candidate code-vector generator comprises:

an inverse filter for constructing an inverse filtered vector from the target vector, where the at least one inverse weighting function is based on the inverse filtered vector.

14. The apparatus according to claim 13,

wherein the inverse filtered vector is constructed based on r=H⁻

1x₂,

wherein r comprises the inverse filtered vector,

wherein H<sup>−

1</sup> comprises a zero-state weighted synthesis convolution matrix formed from an impulse response of a weighted synthesis filter, and

wherein x₂ comprises the target vector.

15. The apparatus according to claim 11, wherein the fixed codebook candidate code-vector generator comprises:

a backward filter for constructing a backward filtered vector from the target vector, where the at least one inverse weighting function is based on the backward filtered vector.

16. The apparatus according to claim 15,

wherein the backward filtered vector is constructed based on d₂=H^Tx₂,

wherein d₂ comprises the backward filtered vector,

wherein H^T comprises a transpose of a zero-state weighted synthesis convolution matrix formed from an impulse response of a weighted synthesis filter, and

wherein x₂ comprises the target vector.

17. The apparatus according to claim 11, wherein an inverse weighting function includes an inverse filtered vector weighted by a weighting coefficient.

18. The apparatus according to claim 11, where an inverse weighting function includes a backward filtered vector weighted by a weighting coefficient.

19. The apparatus according to claim 11, wherein the plurality of candidate code-vectors are based on one of:

an inverse filtered vector constructed from the target vector by an inverse filter and a backward filtered vector constructed from the target vector by a backward filter.

20. The apparatus according to claim 19, further comprising:

a combiner configured to generate the error value based on each of the plurality of candidate code-vectors constructed from the fixed codebook candidate code-vector generator.

21. The apparatus according to claim 11, further comprising a codeword generator configured to generate the codeword based on the fixed codebook code-vector, where the codeword is for use by a decoder to generate an approximation of the input signal.

22. A method comprising:

receiving an input signal based on audible speech;

producing a target vector from the input signal;

constructing a plurality of candidate code-vectors based on the target vector and based on a plurality of inverse weighting functions;

evaluating an error value associated with each of the plurality of candidate code-vectors to produce a fixed codebook code-vector;

generating a codeword representative of the fixed codebook code-vector, where the codeword is used to generate a fixed codebook index parameter that identifies, at least in part, a set of pulse amplitude and position combinations in a codebook used to generate an approximation of the input signal; and

outputting the codeword by one of;

transmitting the codeword or storing the codeword.

23. The method according to claim 22, wherein the constructing comprises:

constructing the plurality of candidate code-vectors based on the target vector, based on a weighted inverse filtered vector, and based on a weighted backward filtered vector.