Learning vector quantization and a temporary memory such that the codebook contents are renewed when a first speaker returns

• US 5,797,118 A
• Filed: 08/08/1995
• Issued: 08/18/1998
• Est. Priority Date: 08/09/1994
• Status: Expired due to Term

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Saito, Akitoshi
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): Collins, Alphonso A.
• Application Number:
  US08/512,311
• Time in Patent Office: 1,106 Days
• Field of Search: 395/2.1, 395/2.15, 395/2.17, 395/2.23, 395/2.31, 395/2.32, 395/2.36, 395/2.67, 395/2.73
• US Class Current: 704/222
• CPC Class Codes: G06T 9/008 Vector quantisation
• 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 2019/0002 Codebook adaptations
• CPC Class Codes: H03M 7/3082 Vector coding for television signals, see H04N19/94

Abstract

An encoding/decoding system employing vector quantization realizes a high quality encoding and decoding with decreased quantizing errors, employing a small sized codebook which faithfully represents each of the inputted waveform vectors. An encoding/decoding system includes an encoding apparatus and a decoding apparatus, each having a codebook for storing information vectors representative of a predetermined number of signal patterns and index that determine the information vectors. The encoding apparatus compares a vector representing an object signal to be quantized with each information vector in the codebook, selects an information vector that is closest to the vector and outputs an index for the information vector. The decoding apparatus obtains an information vector corresponding to the index obtained at the encoding apparatus side by referring to the codebook and decodes the object signal. The codebook utilizes a temporary memory connected thereto. The content of the codebook is temporarily moved to the temporary memory when the identity of the speaker changes. The contents of the temporary memory are read out when the original speakers returns to the system.

Claims

1. A system of encoding/decoding with vector quantization including an encoding apparatus and a decoding apparatus each having a codebook for storing a plurality of information vectors and index that determine the information vectors, the encoding apparatus comparing a vector of an object signal to be quantized with each information vector in the codebook, selecting an information vector that is closest to the vector of the object signal and outputting an index of the selected information vector, the decoding apparatus referring to the codebook to obtain an information vector corresponding to the index obtained by the encoding apparatus and decoding the object signal, the decoding apparatus further comprising:

a temporary memory connected to the codebook, wherein a content of the codebook is temporarily moved to the temporary memory when a first speaker changes to another, and wherein the content temporarily stored in the temporary memory is read out when the first speaker comes back;

an adjacent vector selection observation device that detects selection of a plurality of adjacent information vectors located adjacent to the vector of the object signal from the codebook within a predetermined time period; and

an interpolation vector computation device that interpolates the information vectors based upon selection frequencies of the information vectors and generates an interpolated information vector based upon detection of the plurality of adjacent information vectors, the interpolated information vector being outputted as a decoding result.

2. A system of encoding/decoding with vector quantization including an encoding apparatus and a decoding apparatus each having a codebook for storing information vectors and index that determine the information vectors, the encoding apparatus comparing an object signal to be quantized with each information vector in the codebook, selecting an information vector that is closest to the object signal and outputting an index of the selected information vector, the decoding apparatus referring to the codebook to obtain an information vector corresponding to the index obtained at the encoding apparatus side and decoding the object signal, the encoding apparatus and the decoding apparatus further each comprising:

a temporary memory connected to the codebook, wherein a content of the codebook is temporarily moved to the temporary memory when a first speaker changes to another, and wherein the content temporarily stored in the temporary memory is read out when the first speaker comes back;

an adjacent vector selection observation device that detects selection of a plurality of adjacent information vectors located adjacent to the vector of the object signal from the codebook within a predetermined time period;

an interpolation vector computation device that interpolates the information vectors based upon selection frequencies of the information vectors, and generates a new information vector based upon the detection of the plurality of adjacent information vectors; and

a codebook rewriting device that rewrites one of the information vectors in the codebook with the new information vector generated by the interpolation vector computation device.

3. A system of encoding/decoding with vector quantization in accordance with claim 2, further comprising a rewriting vector determination device that weights the information vectors in the codebook and determines an information vector to be rewritten with the new information vector based upon the weighting.

4. An encoding/decoding system with vector quantization having an encoding apparatus and a decoding apparatus each having a codebook for storing various code vectors and index that determine the respective code vectors, the encoding apparatus using the codebook to compare a vector of an object signal to be quantized with each code vector in the codebook, selecting a code vector that matches most closely the vector of the object signal and outputting an index of the selected code vector, the decoding apparatus obtaining a code vector corresponding to the index obtained at the encoding apparatus side by referring to the codebook and decoding the quantized vector, further the encoding apparatus and the decoding apparatus each having a codebook rewriting device for renewing the content of the codebook based upon a result of matching between the vector to be quantized and the code vector, the system comprising:

a temporary memory connected to the codebook, wherein a content of the codebook is temporarily moved to the temporary memory when a first speaker changes to another, and wherein the content temporarily stored in the temporary memory is read out when the first speaker comes back;

an initialization codebook that stores initial contents of the codebook provided at either of the encoding apparatus and the decoding apparatus;

a characteristic extraction device provided at the encoding apparatus that extracts characteristic parameters of the object signal to be encoded; and

a characteristic change detection device provided at the encoding apparatus that detects at least a change in the characteristic parameters extracted by the characteristic extraction device,

wherein the codebook rewriting device initializes the contents of the codebook with the contents of the initialization codebook when the characteristic change detection device detects the changes in the characteristic parameters.

5. A system of encoding/decoding with vector quantization according to claim 4, further comprising:

a temporary memory device that temporarily stores the contents of the codebook and the characteristic parameters prior to initialization of the codebook; and

wherein the codebook rewriting device compares between the characteristic parameters extracted by the characteristic change detection device and the characteristic parameters stored in the temporary memory device when the characteristic change detection device detects a change in the characteristic parameters, rewrites the contents of the codebook with the contents of the codebook stored in the temporary memory device if these parameters approximate each other, and moves the contents of the codebook to the temporary memory device and initializes the codebook with the contents of the initialization codebook if these characteristic parameters do not approximate each other.

6. A system of encoding/decoding with vector quantization according to claim 5, wherein the encoding apparatus supplies initialization information indicating that the contents of the codebook are rewritten with the contents of the initialization codebook, and the decoding apparatus initializes the contents of the codebook with the contents of the initialization codebook based upon the supplied initialization information.

7. A system of encoding/decoding with vector quantization according to claim 5, wherein:

the encoding apparatus includes a decoder that decodes an encoded result to be outputted, an extractor that performs extraction of characteristic parameters with respect to the decoded result by using the characteristic extraction device and an initializing device that initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected; and

the decoding apparatus includes a decoder that decodes the inputted encoded result, an extractor that performs extraction of the characteristic parameters with respect to the decoded result by using the characteristic extraction device, and an initializing device that initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected.

8. A system of encoding/decoding with vector quantization according to claim 5, wherein the object signal to be encoded is a speech signal, and the characteristic change detection device controls the codebook rewriting device based upon changes in at least one of voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, spectrum envelope information and gain provided by the characteristic extraction device, as well as changes in voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, gain and vector quantization error provided in coding process performed by the encoding apparatus.

9. A system of encoding/decoding with vector quantization according to claim 4, wherein the encoding apparatus supplies initialization information indicating that the contents of the codebook are rewritten with the contents of the initialization codebook, and the decoding apparatus initializes the contents of the codebook with the contents of the initialization codebook based upon the supplied initialization information.

10. A system of encoding/decoding with vector quantization according to claim 4, wherein:

the encoding apparatus includes a decoder that decodes an encoded result to be outputted, an extractor that performs extraction of characteristic parameters with respect to the decoded result by using the characteristic extraction device and an initializing device that initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected; and

the decoding apparatus includes a decoder that decodes the inputted encoded result, an extractor that performs extraction of the characteristic parameters with respect to the decoded result by using the characteristic extraction device, and an initializing device that initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected.

11. A system of encoding/decoding with vector quantization according to claim 4, wherein the object signal to be encoded is a speech signal, and the characteristic change detection device controls the codebook rewriting device based upon changes in at least one of voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, spectrum envelope information and gain provided by the characteristic extraction device, as well as changes in voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, gain and vector quantization error provided in coding process performed by the encoding apparatus.

12. An encoding apparatus with vector quantization, the apparatus comprising:

a codebook that stores a comparison table between a plurality of code vectors and index that determine the respective code vectors;

a vector quantizer that selects a code vector in the codebook that matches most closely a vector to be quantized for an object signal to be encoded and outputs an index corresponding to the code vector;

a codebook rewriting device that adaptively renews the contents of the codebook based upon a result of matching between the vector to be quantized and the code vector;

an initialization codebook that stores the contents in an initial state;

a characteristic extraction device that extracts characteristic parameters of the object signal to be encoded,

wherein the codebook rewriting device initializes the contents of the codebook with the contents of the initialization codebook when the characteristic change detection device detects a change in the characteristic parameters; and

a temporary memory connected to the codebook, wherein a content of the codebook is temporarily moved to the temporary memory when a first speaker changes to another, and wherein the content temporarily stored in the temporary memory is read out when the first speaker comes back.

13. A decoding apparatus with vector quantization, the apparatus comprising:

a codebook that stores a comparison table between a plurality of code vectors and index that determine the respective code vectors;

a vector dequantizer that obtains a code vector corresponding to a received index by referring to the codebook;

a codebook rewriting device that renews the contents of the codebook based upon a received renewal information;

an initialization codebook that stores contents in an initial state,

wherein the codebook rewriting device initializes the contents of the codebook with the contents of the initialization codebook based upon an initialization flag that indicates occurrence of a change in characteristic parameters of an object signal to be encoded; and

a temporary memory connected to the codebook, wherein a content of the codebook is temporarily moved to the temporary memory when a first speaker changes to another, and wherein the content temporarily stored in the temporary memory is read out when the first speaker comes back.

14. A method of encoding/decoding employing vector quantization by an encoding/decoding apparatus, the apparatus including an encoding apparatus and a decoding apparatus each having a codebook for storing a plurality of information vectors and index that determine the information vectors, the encoding apparatus comparing a vector of an object signal to be quantized with each information vector in the codebook, selecting an information vector that is closest to the vector of an object signal and outputting an index of the selected information vector, the decoding apparatus referring to the codebook to obtain an information vector corresponding to the index obtained by the encoding apparatus and decoding the object signal, the method comprising the steps of:

temporarily storing a content of the codebook in a temporary memory when a first speaker changes to another, and reading out the content temporarily stored in the temporary memory when the first speaker comes back;

detecting selection of a plurality of adjacent information vectors located adjacent to the vector of the object signal from the codebook within a predetermined time period; and

interpolating the information vectors based upon selection frequencies of the information vectors and generating an interpolated information vector based upon detection of the plurality of adjacent information vectors, the interpolated information vector being outputted as a decoding result.

15. A method of encoding/decoding employing vector quantization by an encoding/decoding system, the system including an encoding apparatus and a decoding apparatus, each having a codebook for storing information vectors and index that determine the information vectors, the encoding apparatus comparing an object signal to be quantized with each information vector in the codebook, selecting an information vector that is closest to the object signal and outputting an index of the selected information vector, the decoding apparatus referring to the codebook to obtain an information vector corresponding to the index obtained at the encoding apparatus side and decoding the object signal, the method comprising the steps of:

temporarily storing a content of the codebook in a temporary memory when a first speaker changes to another, and reading out the content temporarily stored in the temporary memory when the first speaker comes back;

detecting selection of a plurality of adjacent information vectors located adjacent to the vector of the object signal from the codebook within a predetermined time period in both the encoding apparatus and the decoding apparatus;

interpolating the information vectors based upon selection frequencies of the information vectors, and generating a new information vector based upon the detection of the plurality of adjacent information vectors in both sides of the encoding apparatus and the decoding apparatus; and

rewriting one of the information vectors in the codebook with the new information vector in both the encoding apparatus and the decoding apparatus.

16. A method of encoding/decoding with vector quantization in accordance with claim 15, further comprising the step of weighting the information vector in the codebook and determining an information vector to be rewritten with the new information vector based upon the weighting.

17. A method of encoding/decoding employing vector quantization by an encoding/decoding system, the system having an encoding apparatus and a decoding apparatus, each having a codebook for storing various code vectors and index that determine the respective code vectors, the encoding apparatus using the codebook to compare a vector of an object signal to be quantized with each code vector in the codebook, selecting a code vector that matches most closely the vector of the object signal and outputting an index of the selected code vector, the decoding apparatus obtaining a code vector corresponding to the index obtained at the encoding apparatus side by referring to the codebook and decoding the quantized vector, further the encoding apparatus and the decoding apparatus each having a codebook rewriting device for renewing the content of the codebook based upon a result of matching between the vector to be quantized and the code vector, the method comprising the steps of:

storing initial contents of the codebook provided at both the encoding apparatus and the decoding apparatus;

extracting, at the encoding apparatus, characteristic parameters of the object signal to be encoded;

detecting, at the encoding apparatus, at least a change in the characteristic parameters;

initializing the contents of the codebook with contents of an initialization codebook upon detecting of the changes in the characteristic parameters; and

temporarily storing a content of the codebook in a temporary memory when a first speaker changes to another, and reading out the content temporarily stored in the temporary memory when the first speaker comes back.

18. A method of encoding/decoding with vector quantization according to claim 17, further comprising the steps of:

temporarily storing the contents of the codebook in a buffer memory and the characteristic parameters prior to initialization of the codebook;

comparing between the extracted characteristic parameters and the characteristic parameters stored in the buffer memory upon detection of a change in the characteristic parameters; and

rewriting the contents of the codebook with the contents stored in the buffer memory if the extracted parameters and the parameters temporarily stored in the buffer approximate to each other, and moving the contents of the codebook to the buffer memory and initializing the codebook with the contents of the initialization codebook if the extracted parameters and the parameters temporarily stored in the buffer do not approximate each other.

19. A method of encoding/decoding with vector quantization according to claim 18, wherein the encoding apparatus supplies initialization information indicating that the content of the codebook is rewritten with the content of the initialization codebook, and the decoding apparatus initializes the content of the codebook with the content of the initialization codebook based upon the supplied initialization information.

20. A method of encoding/decoding with vector quantization according to claim 18, wherein:

the encoding apparatus decodes an encoded result to be outputted, performs extraction of characteristic parameters with respect to the decoded result by using the characteristic extraction device and initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected; and

the decoding apparatus decodes the inputted encoded result, performs extraction of the characteristic parameters with respect to the decoded result by using the characteristic extraction device, and initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected.

21. A method of encoding/decoding with vector quantization according to claim 18, wherein the object signal to be encoded is a speech signal, the method further including the step of controlling rewriting of the codebook based upon a change in at least one of voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, spectrum envelope information and gain, as well as changes in voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, gain and vector quantization error provided in coding process performed by the encoding apparatus.

22. A method of encoding/decoding with vector quantization according to claim 17, wherein the encoding apparatus supplies initialization information indicating that the content of the codebook is rewritten with the content of the initialization codebook, and the decoding apparatus initializes the content of the codebook with the content of the initialization codebook based upon the supplied initialization information.

23. A method of encoding/decoding with vector quantization according to claim 17, wherein:

the encoding apparatus decodes an encoded result to be outputted, performs extraction of characteristic parameters with respect to the decoded result by using the characteristic extraction device and initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected; and

the decoding apparatus decodes the inputted encoded result, performs extraction of the characteristic parameters with respect to the decoded result by using the characteristic extraction device, and initializes the contents of the codebook with the contents of the initialization codebook when a change in the extracted characteristic parameters is detected.

24. A method of encoding/decoding with vector quantization according to claim 17, wherein the object signal to be encoded is a speech signal, the method further including the step of controlling rewriting of the codebook based upon a change in at least one of voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, spectrum envelope information and gain, as well as changes in voiced-tone/silence-tone of the speech signal, pitch, characteristic coefficient, gain and vector quantization error provided in coding process performed by the encoding apparatus.

25. A method of encoding employing vector quantization, the method comprising the steps of:

storing a comparison table between a plurality of code vectors and index that determine the respective code vectors in a codebook;

selecting a code vector in the codebook that matches most closely a vector to be quantized for an object signal to be encoded and outputting an index corresponding to the code vector;

adaptively renewing contents of the codebook based upon a result of matching between the vector to be quantized and the code vector;

storing contents in an initial state in an initialization codebook;

extracting characteristic parameters of the object signal to be encoded,

wherein the contents of the codebook is rewritten with the contents of the initialization codebook upon detection of a change in the characteristic parameters; and

temporarily storing a content of the codebook in a temporary memory when a first speaker changes to another, and reading out the content temporarily stored in the temporary memory when the first speaker comes back.

26. A method of decoding employing vector quantization, the method comprising the steps of:

storing a comparison table between a plurality of code vectors and index that determine the respective code vectors in a codebook;

obtaining a code vector corresponding to a received index by referring to the codebook;

renewing contents of the codebook based upon a received renewal information;

storing contents in an initial state in an initialization codebook,

wherein the codebook is initialized with the contents of the initialization codebook based upon an initialization flag that indicates occurrence of a change in characteristic parameters of an object signal to be encoded; and

temporarily storing a content of the codebook in a temporary memory when a first speaker changes to another, and reading out the content temporarily stored in the temporary memory when the first speaker comes back.