Method and Apparatus for Detecting Correctness of Pitch Period

• US 20150073781A1
• Filed: 11/17/2014
• Published: 03/12/2015
• Est. Priority Date: 05/18/2012
• Status: Active Grant

• Current Assignee: Top Quality Telephony LLC
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Qi, Fengyan, Miao, Lei
• Granted Patent: US 9,633,666 B2
• Time in Patent Office: Days
• US Class Current: 704/207
• 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 21/013 Adapting to target pitch
• CPC Class Codes: G10L 21/028 using properties of sound source
• CPC Class Codes: G10L 25/00 Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 muting semiconductor-based amplifiers when some special characteristics of a signal are sensed by a speech detector, e.g. sensing when no signal is present, H03G3/34
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals

Abstract

A method and an apparatus for detecting correctness of a pitch period. The method for detecting correctness of a pitch period includes determining, according to an initial pitch period of an input signal in a time domain, a pitch frequency bin of the input signal, where the initial pitch period is obtained by performing open-loop detection on the input signal; determining, based on an amplitude spectrum of the input signal in a frequency domain, a pitch period correctness decision parameter, associated with the pitch frequency bin, of the input signal; and determining correctness of the initial pitch period according to the pitch period correctness decision parameter. The method and apparatus for detecting correctness of a pitch period according to the embodiments of the present invention can improve, based on a relatively less complex algorithm, accuracy of detecting correctness of a pitch period.

Claims

1. A method for detecting correctness of a pitch period comprising:

determining, according to an initial pitch period of an input signal in a time domain, a pitch frequency bin of the input signal, wherein the initial pitch period is obtained by performing open-loop detection on the input signal;

determining, based on an amplitude spectrum of the input signal in a frequency domain, a pitch period correctness decision parameter of the input signal associated with the pitch frequency bin; and

determining correctness of the initial pitch period according to the pitch period correctness decision parameter.

2. The method according to claim 1, wherein the pitch period correctness decision parameter comprises a spectral difference parameter, an average spectral amplitude parameter, and a difference-to-amplitude ratio parameter, wherein the spectral difference parameter is a sum of spectral differences of a predetermined quantity of frequency bins on two sides of the pitch frequency bin, wherein the average spectral amplitude parameter is an average of spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin, and wherein the difference-to-amplitude ratio parameter is a ratio of the sum of the spectral differences of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin to the average of the spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin.

3. The method according to claim 2, wherein determining the correctness of the initial pitch period according to the pitch period correctness decision parameter comprises:

determining that the initial pitch period is correct when the pitch period correctness decision parameter meets a correctness determining condition; and

determining that the initial pitch period is incorrect when the pitch period correctness decision parameter meets an incorrectness determining condition.

4. The method according to claim 3, wherein the correctness determining condition meets at least one of the following conditions:

the spectral difference parameter is greater than a second difference parameter threshold;

the average spectral amplitude parameter is greater than a second spectral amplitude parameter threshold; and

the difference-to-amplitude ratio parameter is greater than a second ratio factor parameter threshold, and

wherein the incorrectness determining condition meets at least one of the following conditions;

the spectral difference parameter is less than a first difference parameter threshold;

the average spectral amplitude parameter is less than a first spectral amplitude parameter threshold; and

the difference-to-amplitude ratio parameter is less than a first ratio factor parameter threshold.

5. The method according to claim 1, wherein the pitch period correctness decision parameter comprises a spectral difference parameter, an average spectral amplitude parameter, and a difference-to-amplitude ratio parameter, wherein the spectral difference parameter is a weighted and smoothed value of the sum of the spectral differences of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin, wherein the average spectral amplitude parameter is a weighted and smoothed value of the average of the spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin, and wherein the difference-to-amplitude ratio parameter is a ratio of the sum of the spectral differences of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin to the average of the spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin.

6. The method according to claim 1, wherein the method further comprises performing fine detection on the input signal when it is detected that the initial pitch period is incorrect during the detecting, according to the pitch period correctness decision parameter, the correctness of the initial pitch period.

7. The method according to claim 1, wherein, after the determining correctness of the initial pitch period according to the pitch period correctness decision parameter, the method further comprises:

detecting energy in a low-frequency range; and

performing short-pitch detection on the input signal when the energy meets a low-frequency energy determining condition.

8. The method according to claim 1, wherein determining, according to the initial pitch period of the input signal in the time domain, the pitch frequency bin of the input signal comprises that the pitch frequency bin of the input signal is reversely proportional to the initial pitch period and is directly proportional to a quantity of points of a fast Fourier transform performed on the input signal.

9. An apparatus for detecting correctness of a pitch period comprising:

a pitch frequency bin determining unit configured to determine, according to an initial pitch period of an input signal in a time domain, a pitch frequency bin of the input signal, wherein the initial pitch period is obtained by performing open-loop detection on the input signal;

a parameter generating unit configured to determine, based on an amplitude spectrum of the input signal in a frequency domain, a pitch period correctness decision parameter of the input signal associated with the pitch frequency bin; and

a correctness determining unit configured to determine correctness of the initial pitch period according to the pitch period correctness decision parameter.

10. The apparatus according to claim 9, wherein the pitch period correctness decision parameter generated by the parameter generating unit comprises a spectral difference parameter, an average spectral amplitude parameter, and a difference-to-amplitude ratio parameter, wherein the spectral difference parameter is a sum of spectral differences of a predetermined quantity of frequency bins on two sides of the pitch frequency bin, wherein the average spectral amplitude parameter is an average of spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin, and wherein the difference-to-amplitude ratio parameter is a ratio of the sum of the spectral differences of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin to the average of the spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin.

11. The apparatus according to claim 10, wherein the correctness determining unit is configured to:

determine that the initial pitch period is correct when it is determined that the pitch period correctness decision parameter meets a correctness determining condition; and

determine that the initial pitch period is incorrect when it is determined that the pitch period correctness decision parameter meets an incorrectness determining condition.

12. The apparatus according to claim 11, wherein the correctness determining condition meets at least one of the following conditions:

the spectral difference parameter is greater than a second difference parameter threshold;

the average spectral amplitude parameter is greater than a second spectral amplitude parameter threshold; and

the difference-to-amplitude ratio parameter is greater than a second ratio factor parameter threshold, and

wherein the incorrectness determining condition meets at least one of the following conditions;

the spectral difference parameter is less than a first difference parameter threshold;

the average spectral amplitude parameter is less than a first spectral amplitude parameter threshold; and

the difference-to-amplitude ratio parameter is less than a first ratio factor parameter threshold.

13. The apparatus according to claim 9, wherein the pitch period correctness decision parameter generated by the parameter generating unit comprises a spectral difference parameter, an average spectral amplitude parameter, and a difference-to-amplitude ratio parameter, wherein the spectral difference parameter is a weighted and smoothed value of the sum of the spectral differences of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin, wherein the average spectral amplitude parameter is a weighted and smoothed value of the average of the spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin, and wherein the difference-to-amplitude ratio parameter is a ratio of the sum of the spectral differences of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin to the average of the spectral amplitudes of the predetermined quantity of frequency bins on the two sides of the pitch frequency bin.

14. The apparatus according to claim 9 further comprising a fine detecting unit configured to perform fine detection on the input signal, when it is detected that the initial pitch period is incorrect during the detecting, according to the pitch period correctness decision parameter, the correctness of the initial pitch period.

15. The apparatus according to claim 9 further comprising:

an energy detecting unit configured to detect energy of the initial pitch period in a low-frequency range, when an incorrect initial pitch period is detected during the detecting, according to the pitch period correctness decision parameter, the correctness of the initial pitch period; and

a fine detecting unit configured to perform short-pitch detection on the input signal when the energy meets a low-frequency energy determining condition.

16. The apparatus according to claim 9, wherein the pitch frequency bin determining unit is configured to determine the pitch frequency bin based on the following condition:

the pitch frequency bin of the input signal is reversely proportional to the initial pitch period and is directly proportional to a quantity of points of a fast Fourier transform performed on the input signal.