Encoding method, decoding method, encoder apparatus, decoder apparatus, and recording medium for processing pitch periods corresponding to time series signals

Patent metadata

Field	Value
Publication number	US-9812141-B2
Application number	US-201113518525-A
Country	US
Kind code	B2
Filing date	Jan 7, 2011
Priority date	Jan 8, 2010
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

In encoding, pitch periods for time series signals in a predetermined time interval are calculated, and a code corresponding thereto is output. In that encoding, the resolutions for expressing the pitch periods and/or a pitch period encoding mode are switched according to whether an index indicating a periodicity and/or stationarity level of the time series signals satisfies a condition indicating high or low in periodicity and/or stationarity. In that decoding, according to whether an index indicating a periodicity and/or stationarity level, the index being included in or obtained from an input code corresponding to the predetermined time interval, satisfies a condition indicating high periodicity and/or stationarity, a decoding mode for a code, included in the input code, corresponding to pitch periods is switched to decode the code corresponding to the pitch periods to obtain the pitch periods corresponding to the predetermined time interval.

First claim

What is claimed is:

1. An encoding method comprising:
(A) a step of obtaining pitch periods corresponding to time series signals included in a predetermined time interval; and
(B) a step of outputting a code corresponding to the pitch periods;
wherein the step (B) comprises a step of outputting the code obtained by encoding the pitch periods expressed at a first quantization resolution when an index that indicates a level of stationarity of the time series signals does not satisfy the condition that indicates high stationarity, and
of outputting the code obtained by encoding the pitch periods expressed at a second quantization resolution when the index satisfies the condition that indicates high stationarity; and
the second quantization resolution is higher than the first quantization resolution.

2. The encoding method according to claim 1 ,
wherein the step (A) further comprises a step of obtaining a quantized pitch gain corresponding to the time series signals;
the index includes the quantized pitch gain or a value corresponding thereto; and
the condition that indicates high stationarity includes a condition in which the quantized pitch gain or the value corresponding thereto is larger than a specified value.

3. The encoding method according to claim 1 ,
wherein the step (A) further comprises a step of obtaining a vector-quantized gain code corresponding to a combination of a quantized pitch gain corresponding to the time series signals or a value corresponding to the quantized pitch gain, and a quantized fixed-codebook gain corresponding to the time series signals or a value corresponding to the quantized fixed-codebook gain;
the index includes the vector-quantized gain code; and
the condition that indicates high stationarity includes a condition in which the vector-quantized gain code corresponds to a combination of a quantized pitch gain that is larger than a specified value or a value that corresponds to the quantized pitch gain and that is larger than the specified value, and the quantized fixed-codebook gain or the value corresponding thereto.

4. The encoding method according to claim 1 ,
wherein the step (A) further comprises a step of obtaining a quantized pitch gain corresponding to the time series signals and a quantized fixed-codebook gain corresponding to the time series signals;
the index includes the quantized pitch gain or a value corresponding thereto, and the quantized fixed-codebook gain or a value corresponding thereto; and
the condition that indicates high stationarity includes a condition in which the ratio of the quantized pitch gain or the value corresponding thereto to the quantized fixed-codebook gain or the value corresponding thereto is larger than a specified value.

5. The encoding method according to claim 1 ,
wherein the step (A) further comprises a step of obtaining a vector-quantized gain code corresponding to a combination of a quantized pitch gain corresponding to the time series signals or a value corresponding to the quantized pitch gain, and a quantized fixed-codebook gain corresponding to the time series signals or a value corresponding to the quantized fixed-codebook gain;
the index includes the vector-quantized gain code; and
the condition that indicates high stationarity includes a condition in which the vector-quantized gain code corresponds to a combination of a quantized pitch gain or a value corresponding thereto, and a quantized fixed-codebook gain or a value corresponding thereto where the ratio of the quantized pitch gain or the value corresponding thereto to the quantized fixed-codebook gain or the value corresponding thereto is larger than a specified value.

6. The encoding method according to claim 1 ,
wherein the step (A) further comprises a step of obtaining a quantized pitch gain corresponding to the time series signals and a quantized fixed-codebook gain corresponding to the time series signals;
the index includes the quantized pitch gain or a value corresponding thereto and the quantized fixed-codebook gain or a value corresponding thereto; and
the condition that indicates low stationarity includes a condition in which the quantized pitch gain or the value corresponding thereto is smaller than a first specified value and the quantized fixed-codebook gain or the value corresponding thereto is smaller than a second specified value.

7. The encoding method according to claim 1 ,
wherein the step (A) further comprises a step of obtaining a vector-quantized gain code corresponding to a combination of a quantized pitch gain corresponding to the time series signals or a value corresponding to the quantized pitch gain, and a quantized fixed-codebook gain corresponding to the time series signals or a value corresponding to the quantized fixed-codebook gain;
the index includes the vector-quantized gain code; and
the condition that indicates low stationarity includes a condition in which the quantized pitch gain corresponding to the vector-quantized gain code or the value corresponding to the quantized pitch gain is smaller than a first specified value and the quantized fixed-codebook gain corresponding to the vector-quantized gain code or the value corresponding to the quantized fixed-codebook gain is smaller than a second specified value.

8. The encoding method according to claim 1 ,
wherein the step (A) further comprises a step of obtaining a vector-quantized gain code corresponding to a combination of a quantized pitch gain corresponding to the time series signals or a value corresponding to the quantized pitch gain, and a quantized fixed-codebook gain corresponding to the time series signals or a value corresponding to the quantized fixed-codebook gain;
the index includes the vector-quantized gain code; and
the encoding mode is switched according to the vector-quantized gain code while referencing a table in which each vector-quantized gain code is associated with a resolution used to express a pitch period and/or a pitch period encoding mode.

9. The encoding method according to claim 1 ,
wherein the index includes an index that indicates the ratio of the magnitude of the time series signals to the magnitude of prediction residuals obtained by applying linear prediction analysis to the time series signals; and
the condition that indicates high stationarity includes a condition in which the index that indicates the ratio of the magnitude of the time series signals to the magnitude of the prediction residuals obtained by applying linear prediction analysis to the time series signals is larger than a specified value.

10. The encoding method according to claim 1 ,
wherein the index includes the magnitude of the difference between a value corresponding to a pitch period in a time interval included in the predetermined time interval and a value corresponding to a pitch period in a past time interval before the time interval included in the predetermined time interval; and
the condition that indicates high stationarity includes a condition in which the magnitude of the difference between the value corresponding to the pitch period in the time interval included in the predetermined time interval and the value corresponding to the pitch period in the past time interval before the time interval included in the predetermined time interval is smaller than a specified value.

11. A decoding method comprising:
receiving of a code corresponding to a predetermined time interval; and
decoding a pitch code included in the code to obtain the pitch periods corresponding to the predetermined time interval;
wherein the pitch code corresponding to the pitch periods is decoded with a decoding mode that obtains each of the pitch pe

Assignees

• Moriya Takehiro
• Harada Noboru
• Kamamoto Yutaka
• Nippon Telegraph & Telephone

Inventors

• Moriya Takehiro
• Harada Noboru
• Kamamoto Yutaka

Classifications

• G10L19/09 Primary

  Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor · CPC title

• G10L19/08 Primary

  Determination or coding of the excitation function; Determination or coding of the long-term prediction parameters · CPC title

• G10L19/032

  Quantisation or dequantisation of spectral components · CPC title