Pitch cycle search range setting apparatus and pitch cycle search apparatus

• US 20040030545A1
• Filed: 03/21/2003
• Published: 02/12/2004
• Est. Priority Date: 08/02/2001
• Status: Active Grant

• Current Assignee: III Holdings 12, LLC (Intellectual Ventures LLC)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Sato, Kaoru, Yasunaga, Kazutoshi, Morii, Toshiyuki
• Granted Patent: US 7,177,802 B2
• Time in Patent Office: Days
• US Class Current: 704/207
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 19/125 Pitch excitation, e.g. pitch synchronous innovation CELP [PSI-CELP]
• CPC Class Codes: G10L 2019/0002 Codebook adaptations
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals

Abstract

An Adaptive Sound Source Vector Generator (ASSVG) 103 sets preceding and succeeding pitch cycles centered on an integral-accuracy pitch cycle T0 selected in the previous subframe as a range for searching for a fractional-accuracy pitch frequency, and extracts an adaptive sound source vector P(T-frac) that has fractional-accuracy pitch cycle T-frac within this range from an Adaptive Code Book (ACB) 102. A Last Sub Frame Integral Pitch Cycle Storage (LSFIPCS) 108 stores integral component T0 of the optimal pitch cycle selected by a Distortion Comparator (DC) 107, and when a pitch cycle of the next subframe is searched for, outputs this optimal pitch cycle integral component T0 to the Adaptive Sound Source Vector Generator (ASSVG) 103. An Optimal Pitch Cycle Accuracy Judge Section (OPCAJS) 109 judges whether the optimal pitch cycle is of integral accuracy or fractional accuracy. A Comparison Judge Section (CJS) 110 restricts the number of times fractional-accuracy pitch information is selected in an optimal pitch cycle.

Claims

1. A pitch cycle search range setting apparatus comprising:

a pitch cycle indicating section that, in pitch cycle search processing that searches for a pitch cycle included in a linear predictive residual on a subframe basis, sequentially indicates pitch cycle candidates within a preset pitch cycle search range with integral accuracy to an adaptive sound source vector generating section;

an adaptive sound source vector generating section that extracts an adaptive sound source vector that has a pitch cycle indicated by said pitch cycle indicating section from an adaptive code book that stores past drive sound sources; and

a last subframe integral pitch cycle storage section that stores the integral component of a pitch cycle finally selected in pitch cycle search processing of a previous subframe;

wherein said pitch cycle search range setting apparatus sets as a pitch cycle search object, in processing subframe section pitch cycle search processing, both or one of an integral-accuracy pitch cycle candidate indicated by said pitch cycle indicating section and a fractional-accuracy pitch cycle search candidate that covers with fractional-accuracy a pitch cycle in the vicinity of an integral-accuracy pitch cycle read from said last subframe integral pitch cycle storage section.

2. The pitch cycle search range setting apparatus according to claim 1, further comprising:

a comparison judging section provided with a comparison judging function that performs relative size comparison of a value of a counter provided internally and a non-negative integer N; and

an optimal pitch cycle accuracy judging section that has a function that judges whether a pitch cycle selected as an optimal pitch cycle in processing subframe pitch cycle search processing is of integral accuracy or of fractional accuracy, and manipulates a value of said counter provided in said comparison judging section in accordance with a result of that judgment;

wherein said pitch cycle search range setting apparatus performs pitch cycle search processing only for said integral-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is greater than said N, and performs a pitch cycle search for both said integral-accuracy pitch cycle search candidate and said fractional-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is less than or equal to said N.

3. The pitch cycle search range setting apparatus according to claim 2, wherein said optimal pitch cycle accuracy judging section executes an operation that resets a value of said internal counter of said comparison judging section to 0 when accuracy of a pitch cycle selected finally in processing subframe section pitch cycle search processing is integral accuracy, and executes an operation that increments said internal counter of said comparison judging section when accuracy of a pitch cycle selected finally in processing subframe section pitch cycle search processing is fractional accuracy.

4. A pitch cycle search apparatus comprising:

an adaptive sound source vector generating section that extracts from an adaptive code book an adaptive sound source vector that has an integral-accuracy pitch cycle indicated by said pitch cycle indicating section, and outputs that extracted adaptive sound source vector to an integral-accuracy pitch cycle search section and a fractional pitch cycle adaptive sound source vector generating section;

an integral-accuracy pitch cycle search section that performs a closed-loop search for an integral-accuracy pitch cycle using an adaptive sound source vector received from said adaptive sound source vector generating section, and outputs an integral-accuracy optimal pitch cycle index and selection measure to a distortion comparison section;

a fractional pitch cycle adaptive sound source vector generating section that complements an integral-accuracy adaptive sound source vector received from said adaptive sound source vector generating section and generates an adaptive sound source vector that has a fractional-accuracy pitch cycle, and outputs that generated adaptive sound source vector that has a fractional-accuracy pitch cycle to a fractional-accuracy pitch cycle search section;

a fractional-accuracy pitch cycle search section that performs a closed-loop search for a fractional-accuracy pitch cycle using an adaptive sound source vector that has a fractional-accuracy pitch cycle received from said fractional pitch cycle adaptive sound source vector generating section, and outputs a fractional-accuracy optimal pitch cycle index and selection measure to said distortion comparison section; and

a comparison section that has a function that compares a selection measure received from said integral-accuracy pitch cycle search section with a selection measure received from said fractional-accuracy pitch cycle search section, and outputs an index with a larger selection measure as an index indicating a processing subframe section optimal pitch cycle, and a function that outputs an integral component of a pitch cycle with a larger selection measure to said last subframe integral pitch cycle storage section;

wherein said pitch cycle search apparatus searches for a pitch cycle possessed by a processing subframe section linear predictive residual from among pitch cycle candidates within a range set by the pitch cycle search range setting apparatus according to claim 1.

5. A pitch cycle search apparatus comprising:

an adaptive sound source vector generating section that extracts adaptive sound source vectors that have an integral-accuracy pitch cycle indicated by said pitch cycle indicating section from an adaptive code book, and outputs those extracted adaptive sound source vectors to an integral-accuracy pitch cycle search section and fractional pitch cycle adaptive sound source vector generating section; and

a distortion comparison section that has a function that finds an index indicating an optimal pitch cycle among processing subframe section linear predictive residuals by means of a two-stage search, comprising an open-loop search and closed-loop search, on an adaptive sound source vector that has an integral-accuracy pitch cycle generated by an adaptive sound source vector generating section and an adaptive sound source vector that has a fractional-accuracy pitch cycle obtained by interpolating an adaptive sound source vector that has an integral-accuracy pitch cycle generated by said adaptive sound source vector generating section, and a function that outputs an optimal pitch cycle integral component to a last subframe integral pitch cycle storage section;

wherein said pitch cycle search apparatus searches for an optimal pitch cycle from with in a pitch cycle search range set by the pitch cycle search range setting apparatus according to claim 1.

6. The pitch cycle search apparatus according to claim 4, further comprising:

a comparison judging section provided with a comparison judging function that performs relative size comparison of a value of a counter provided internally and a non-negative integer N; and

an optimal pitch cycle accuracy judging section that has a function that judges whether a pitch cycle selected as an optimal pitch cycle in processing subframe pitch cycle search processing is of integral accuracy or of fractional accuracy, and manipulates a value of said counter provided in said comparison judging section in accordance with a result of that judgment;

and comprising a pitch cycle search range setting apparatus that performs pitch cycle search processing only for said integral-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is greater than said N, and performs a pitch cycle search for both said integral-accuracy pitch cycle search candidate and said fractional-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is less than or equal to said N;

wherein always and irrespective of a subframe number, a value of said non-negative integer N, for which pitch cycle search processing should be performed for both a fractional-accuracy pitch cycle candidate and integral-accuracy pitch cycle candidate, is set beforehand to infinitude.

7. The pitch cycle search apparatus according to claim 4, further comprising:

a comparison judging section provided with a comparison judging function that performs relative size comparison of a value of a counter provided internally and a non-negative integer N; and

an optimal pitch cycle accuracy judging section that has a function that judges whether a pitch cycle selected as an optimal pitch cycle in processing subframe pitch cycle search processing is of integral accuracy or of fractional accuracy, and manipulates a value of said counter provided in said comparison judging section in accordance with a result of that judgment;

and comprising a pitch cycle search range setting apparatus that performs pitch cycle search processing only for said integral-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is greater than said N, and performs a pitch cycle search for both said integral-accuracy pitch cycle search candidate and said fractional-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is less than or equal to said N;

wherein an arbitrary natural number is set for said non-negative integer N which should set an upper limit of a consecutive number of subframes for which accuracy of a pitch cycle selected finally is fractional accuracy.

8. The pitch cycle search apparatus according to claim 4, further comprising:

a comparison judging section provided with a comparison judging function that performs relative size comparison of a value of a counter provided internally and a non-negative integer N; and

an optimal pitch cycle accuracy judging section that has a function that judges whether a pitch cycle selected as an optimal pitch cycle in processing subframe pitch cycle search processing is of integral accuracy or of fractional accuracy, and manipulates a value of said counter provided in said comparison judging section in accordance with a result of that judgment;

and comprising a pitch cycle search range setting apparatus that performs pitch cycle search processing only for said integral-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is greater than said N, and performs a pitch cycle search for both said integral-accuracy pitch cycle search candidate and said fractional-accuracy pitch cycle search candidate when a value of said internal counter of said comparison judging section is less than or equal to said N;

wherein a value of non-negative integer N can be varied in accordance with a degree of index transmission error occurrence frequency.

9. The pitch cycle search apparatus according to claim 7, wherein, in a fractional-accuracy pitch cycle search, when a value of said counter is greater than non-negative integer N that is an object of comparison, a fractional-accuracy pitch cycle search is performed within a predetermined range, and when a value of said counter is greater than non-negative integer N that is an object of comparison, said counter is reset to 0 irrespective of whether a pitch cycle chosen as an optimal pitch cycle is of integral accuracy or of fractional accuracy.

10. The pitch cycle search apparatus according to claim 9, wherein, in said fractional-accuracy pitch cycle search section, when a value of said counter is greater than a value of non-negative integer N that is an object of comparison, said fractional-accuracy pitch cycle search and a fractional-accuracy pitch cycle search in a section with a short pitch cycle are performed.

12. A speech encoding apparatus comprising:

the pitch cycle search apparatus according to claim 4;

a fixed sound source vector generating section that generates a fixed sound source vector from a fixed code book;

a section that performs quantization and encoding of a parameter indicating a spectral characteristic of an input speech signal;

a section that synthesizes a composite speech signal using a sound source vector generated from said fixed sound source vector generating section and said adaptive sound source vector pitch cycle search apparatus and said parameter; and

a section that determines output from said fixed sound source vector generating section and said adaptive sound source vector pitch cycle search apparatus so that distortion of said input speech signal and said composite speech signal becomes small.

14. A speech signal transmitting apparatus comprising:

a speech input apparatus that converts a speech signal to an electrical signal;

an A/D conversion apparatus that converts a signal output by said speech input apparatus to a digital signal;

the speech encoding apparatus according to claim 12 that performs encoding of a digital signal output from said A/D conversion apparatus;

an RF modulation apparatus that performs modulation processing and so forth on encoded information output from said speech encoding apparatus; and

a transmitting antenna that converts a signal output from said RF modulation apparatus to a radio wave and transmits that radio wave.

16. A mobile station apparatus that has a speech signal transmitting apparatus and performs radio communications with a base station apparatus, said speech signal transmitting apparatus comprising:

a speech input apparatus that converts a speech signal to an electrical signal;

an A/D conversion apparatus that converts a signal output by said speech input apparatus to a digital signal;

the speech encoding apparatus according to claim 12 that performs encoding of a digital signal output from said A/D conversion apparatus;

an RF modulation apparatus that performs modulation processing and so forth on encoded information output from said speech encoding apparatus; and

a transmitting antenna that converts a signal output from said RF modulation apparatus to a radio wave and transmits that radio wave.

18. A base station apparatus that has a speech signal transmitting apparatus and performs radio communications with a mobile station apparatus, said speech signal transmitting apparatus comprising:

a speech input apparatus that converts a speech signal to an electrical signal;

an A/D conversion apparatus that converts a signal output by said speech input apparatus to a digital signal;

the speech encoding apparatus according to claim 12 that performs encoding of a digital signal output from said A/D conversion apparatus;

an RF modulation apparatus that performs modulation processing and so forth on encoded information output from said speech encoding apparatus; and

a transmitting antenna that converts a signal output from said RF modulation apparatus to a radio wave and transmits that radio wave.

11. A decoding adaptive sound source vector generating apparatus comprising:

a last subframe integral pitch cycle storage section that has a function that stores a pitch cycle selected in a previous subframe section;

a pitch cycle judging section that has a function that finds an optimal adaptive sound source vector pitch cycle using a pitch cycle selected in a previous subframe received from said last subframe integral pitch cycle storage section and an index received as input, and passes that optimal adaptive sound source vector pitch cycle to an adaptive sound source vector generating section;

an adaptive sound source vector generating section that has a function that extracts from an adaptive code book an adaptive sound source vector that has a pitch cycle received from said pitch cycle judging section, outputs that extracted adaptive sound source vector if a pitch cycle is of integral accuracy, or outputs that extracted adaptive sound source vector to a fractional pitch cycle adaptive sound source vector generating section if a pitch cycle is of fractional accuracy; and

a fractional pitch cycle adaptive sound source vector generating section that has a function that generates and outputs an adaptive sound source vector that has a fractional-accuracy pitch cycle from an adaptive sound source vector received from said adaptive sound source vector generating section.

13. A speech decoding apparatus comprising:

a section that decodes an index indicating an adaptive sound source vector pitch cycle encoded by a speech encoding apparatus using the decoding adaptive sound source vector generating apparatus according to claim 11;

a fixed sound source vector generating section that generates a fixed sound source vector from a fixed code book;

a section that decodes a parameter indicating a spectral characteristic encoded by said speech encoding apparatus; and

a section that decodes a sound source vector determined in said speech encoding apparatus from said fixed sound source vector generating section and said decoding adaptive sound source vector generating apparatus, and synthesizes a composite speech signal from a decoded sound source vector and said parameter.

15. A speech signal receiving apparatus comprising:

a receiving antenna that receives a reception radio wave;

an RF demodulation apparatus that performs demodulation processing on a signal received by said receiving antenna;

the speech decoding apparatus according to claim 13 that performs decoding processing on information obtained by said RF demodulation apparatus;

a D/A conversion apparatus that performs D/A conversion of a digital speech signal decoded by said speech decoding apparatus; and

a speech output apparatus that converts an electrical signal output from said D/A conversion apparatus to a speech signal.

17. A mobile station apparatus that has a speech signal receiving apparatus and performs radio communications with a base station apparatus, said speech signal receiving apparatus comprising:

a receiving antenna that receives a reception radio wave;

an RF demodulation apparatus that performs demodulation processing on a signal received by said receiving antenna;

the speech decoding apparatus according to claim 13 that performs decoding processing on information obtained by said RF demodulation apparatus;

a D/A conversion apparatus that performs D/A conversion of a digital speech signal decoded by said speech decoding apparatus; and

a speech output apparatus that converts an electrical signal output from said D/A conversion apparatus to a speech signal.

19. A base station apparatus that has a speech signal receiving apparatus and performs radio communications with a mobile station apparatus, said speech signal receiving apparatus comprising:

a receiving antenna that receives a reception radio wave;

an RF demodulation apparatus that performs demodulation processing on a signal received by said receiving antenna;

the speech decoding apparatus according to claims 13 that performs decoding processing on information obtained by said RF demodulation apparatus;

a D/A conversion apparatus that performs D/A conversion of a digital speech signal decoded by said speech decoding apparatus; and

a speech output apparatus that converts an electrical signal output from said D/A conversion apparatus to a speech signal.