ENCODER, DECODER, CODING METHOD, DECODING METHOD, CODING PROGRAM, DECODING PROGRAM AND RECORDING MEDIUM

• US 20170040023A1
• Filed: 02/20/2015
• Published: 02/09/2017
• Est. Priority Date: 05/01/2014
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: MORIYA, Takehiro, KAMAMOTO, Yutaka, HARADA, Noboru
• Granted Patent: US 10,199,046 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/04 using predictive techniques
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• 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 25/90 Pitch determination of speech signals
• CPC Class Codes: H03M 7/40 Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code

Abstract

An encoder includes a periodic-combined-envelope generating part and a variable-length coding part. The periodic-combined-envelope generating part generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input audio signal and on a frequency-domain period. The variable-length coding part encodes a frequency-domain sequence derived from the input audio signal. A decoder includes a periodic-combined-envelope generating part and a variable-length decoding part. The periodic-combined-envelope generating part generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code and on a frequency-domain period. The variable-length decoding part decodes a variable-length code to obtain a frequency-domain sequence.

Claims

1. :

An encoder comprising;

a periodic-combined-envelope generating part which generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input audio signal in a predetermined time segment and on a frequency-domain period corresponding to a period code obtained from the input audio signal;

a variable-length-coding-parameter calculating part which calculates a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and

a variable-length coding part which uses a variable-length coding parameter to encode a frequency-domain sequence derived from the input audio signal by variable-length coding dependent on an amplitude value.

3. :

The encoder according to claim 1, further comprising a second variable-length-coding-parameter calculating part which calculates a variable-length coding parameter dependent on an amplitude value from the spectral envelope sequence,

wherein when an indicator of the degree of periodicity of the input audio signal is within a predetermined range indicating high periodicity, the variable-length coding part uses a variable-length coding parameter calculated by the variable-length-coding-parameter calculating part to perform encoding; and

when the indicator of the degree of periodicity is not within the range indicating high periodicity, the variable-length coding part uses a variable-length-coding parameter calculated by the second variable-length-coding-parameter calculating part to perform encoding.

17. :

A coding program for causing a computer to function as the encoder according to any one of claims 1 to 4.

19. :

A non-transitory computer-readable recording medium on which the coding program for causing a computer to function as the encoder according to any one of claims 1 to 4 is recorded.

21. :

The encoder according to any one of claims 1 to 4,

wherein the periodic-combined-envelope generating part obtains, as a periodic combined envelope sequence, a sequence that can be obtained by more greatly changing values of at least samples at integer multiples of a period in the frequency-domain of the input audio signal in the spectral envelope sequence and samples in a neighborhood of the integer multiples of the period as the length of a period in the frequency domain of the input audio signal is longer.

22. :

The encoder according to any one of claims 1 to 4,

wherein the periodic-combined-envelope generating part obtains, as a periodic combined envelope sequence, a sequence that is obtained by changing values of a larger number of samples in a neighborhood of integer multiples of a period of the frequency domain of the input audio signal in the amplitude spectral envelope sequence as the length of a period in the frequency domain of the input audio signal is longer.

2. :

An encoder comprising;

a periodic-combined-envelope generating part which generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input audio signal in a predetermined time segment and on a frequency-domain period corresponding to a period code obtained from the input audio signal; and

a variable-length coding part which encodes a frequency-domain sequence derived from the input audio signal on the assumption that the amplitude of the input audio signal is greater for a frequency with a greater value of the periodic-combined envelope sequence.

4. :

The encoder according to claim 2,

wherein when an indicator of the degree of periodicity of the input audio signal is within a predetermined range indicating high periodicity, the variable-length coding part encodes a frequency-domain sequence derived from the input audio signal on the assumption that the amplitude of the input audio signal is greater for a frequency with a greater value of the periodic combined envelope sequence; and

when the indicator is not within the range indicating high periodicity, the variable-length coding part encodes a frequency-domain sequence derived from the input audio signal on the assumption that the amplitude of the input audio signal is greater for a frequency with a greater value of the spectral envelope sequence.

5. :

A decoder comprising;

a periodic-combined-envelope generating part which generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code and on a frequency-domain period corresponding to a period code;

a variable-length-coding-parameter calculating part which calculates a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and

a variable-length decoding part which uses a variable-length coding parameter to perform decoding.

7. :

The decoder according to claim 5 further comprising;

an indicator decoding part which decodes an input indicator code to obtain an indicator of the degree of periodicity; and

a second variable-length-coding-parameter calculating part which calculates a variable-length coding parameter dependent on an amplitude value from the spectral envelope sequence;

wherein when the indicator is within a predetermined range indicating high periodicity, the variable-length coding part uses a variable-length coding parameter calculated by the variable-length-coding-parameter calculating part to perform decoding; and

when the indicator is not within the range indicating high periodicity, the variable-length decoding part uses a variable-length coding parameter calculated by the second variable-length-coding-parameter calculating part to perform decoding.

18. :

A decoding program for causing a computer to function as the decoder according to any one of claims 5 to 8.

20. :

A non-transitory computer-readable recording medium on which the decoding program for causing a computer to function as the decoder according to any one of claims 5 to 8 is recorded.

23. :

The decoder according to any one of claims 5 to 8,

wherein the periodic-combined-envelope generating part obtains, as a periodic combined envelope sequence, a sequence that can be obtained by more greatly changing values of at least samples at integer multiples of a period in the frequency-domain corresponding to the period code in the spectral envelope sequence and samples in a neighborhood of the integer multiples of the period as the length of a period in the frequency domain corresponding to the period code is longer.

24. :

The decoder according to any one of claims 5 to 8,

wherein the periodic-combined-envelope generating part obtains, as a periodic combined envelope sequence, a sequence that is obtained by changing values of a larger number of samples in a neighborhood of integer multiples of a period of the frequency domain corresponding to the period code in the amplitude spectral envelope sequence as the length of a period in the frequency domain corresponding to the period code is longer.

6. :

A decoder comprising;

a periodic-combined-envelope generating part which generates a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code and on a frequency-domain period corresponding to a period code; and

a variable-length decoding part which decodes a variable-length code to obtain a frequency-domain sequence on the assumption that the amplitude of an audio signal is greater for a frequency with a greater value of the periodic combined envelope sequence.

8. :

The decoder according to claim 6,

wherein when an input indicator of the degree of periodicity is within a predetermined range indicating high periodicity, the variable-length decoding part decodes the variable-length code to obtain a frequency-domain sequence on the assumption that the amplitude of an audio signal is greater for a frequency with a greater value of the periodic combined envelope sequence; and

when the indicator is not within the predetermined range indicating high periodicity, the variable-length decoding part decodes the variable-length code to obtain a frequency-domain sequence on the assumption that the amplitude of an audio signal is greater for a frequency with a greater value of the spectral envelope sequence.

9. :

A coding method executing;

a periodic-combined-envelope generating step of generating a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input audio signal in a predetermined time segment and on a frequency-domain period corresponding to a period code obtained from the input audio signal;

a variable-length-coding-parameter calculating step of calculating a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and

a variable-length coding step of using a variable-length coding parameter to encode a frequency-domain sequence derived from the input audio signal by variable-length coding dependent on an amplitude value.

11. :

The coding method according to claim 9, further comprising a second variable-length-coding-parameter calculating step of calculating a variable-length coding parameter dependent on an amplitude value from the spectral envelope sequence,

wherein when an indicator of the degree of periodicity of the input audio signal is within a predetermined range indicating high periodicity, the variable-length coding step uses a variable-length coding parameter calculated in the variable-length-coding-parameter calculating step to perform encoding; and

when the indicator of the degree of periodicity is not within the range indicating high periodicity, the variable-length coding step uses a variable-length-coding parameter calculated in the second variable-length-coding-parameter calculating step to perform encoding.

10. :

A coding method executing;

a periodic-combined-envelope generating step of generating a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code obtained from an input audio signal in a predetermined time segment and on a frequency-domain period corresponding to a period code obtained from the input audio signal; and

a variable-length coding step of encoding a frequency-domain sequence derived from the input audio signal on the assumption that the amplitude of the input audio signal is greater for a frequency with a greater value of the periodic-combined envelope sequence.

12. :

The coding method according to claim 10,

wherein when an indicator of the degree of periodicity of the input audio signal is within a predetermined range indicating high periodicity, the variable-length coding step encodes a frequency-domain sequence derived from the input audio signal on the assumption that the amplitude of the input audio signal is greater for a frequency with a greater value of the periodic combined envelope sequence; and

when the indicator is not within the range indicating high periodicity, the variable-length coding step encodes a frequency-domain sequence derived from the input audio signal on the assumption that the amplitude of the input audio signal is greater for a frequency with a greater value of the spectral envelope sequence.

25. :

The coding method according to any one of claims 9 to 12,

wherein the periodic-combined-envelope generating step obtains, as a periodic combined envelope sequence, a sequence that can be obtained by more greatly changing values of at least samples at integer multiples of a period in the frequency-domain of the input audio signal in the spectral envelope sequence and samples in a neighborhood of the integer multiples of the period as the length of a period in the frequency domain of the input audio signal is longer.

26. :

The coding method to any one of claims 9 to 12,

wherein the periodic-combined-envelope generating step obtains, as a periodic combined envelope sequence, a sequence that is obtained by changing values of a larger number of samples in a neighborhood of integer multiples of a period of the frequency domain of the input audio signal in the amplitude spectral envelope sequence as the length of a period in the frequency domain of the input audio signal is longer.

13. :

A decoding method executing;

a periodic-combined-envelope generating step of generating a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code and on a frequency-domain period corresponding to a period code;

a variable-length-coding-parameter calculating step of calculating a variable-length coding parameter dependent on an amplitude value from the periodic combined envelope sequence; and

a variable-length decoding step of using a variable-length coding parameter to perform decoding.

15. :

The decoding method according to claim 13, further comprising;

an indicator decoding step of decoding an input indicator code to obtain an indicator of the degree of periodicity; and

a second variable-length-coding-parameter calculating step of calculating a variable-length coding parameter dependent on an amplitude value from the spectral envelope sequence;

wherein when the indicator is within a predetermined range indicating high periodicity, the variable-length decoding step uses a variable-length coding parameter calculated by the variable-length-coding-parameter calculating step to perform decoding; and

when the indicator is not within the range indicating high periodicity, the variable-length decoding step uses a variable-length coding parameter calculated by the second variable-length-coding-parameter calculating step to perform decoding.

27. :

The decoding method according to any one of claims 13 to 16,

wherein the periodic-combined-envelope generating step obtains, as a periodic combined envelope sequence, a sequence that can be obtained by more greatly changing values of at least samples at integer multiples of a period in the frequency-domain corresponding to the period code in the spectral envelope sequence and samples in a neighborhood of the integer multiples of the period as the length of a period in the frequency domain corresponding to the period code is longer.

28. :

The decoding method according to any one of claims 13 to 16,

wherein the periodic-combined-envelope generating step obtains, as a periodic combined envelope sequence, a sequence that is obtained by changing values of a larger number of samples in a neighborhood of integer multiples of a period of the frequency domain corresponding to the period code in the amplitude spectral envelope sequence as the length of a period in the frequency domain corresponding to the period code is longer.

14. :

A decoding method executing;

a periodic-combined-envelope generating step of generating a periodic combined envelope sequence which is a frequency-domain sequence based on a spectral envelope sequence which is a frequency-domain sequence corresponding to a linear predictive coefficient code and on a frequency-domain period corresponding to a period code; and

a variable-length decoding step of decoding a variable-length code to obtain a frequency-domain sequence on the assumption that the amplitude of an audio signal is greater for a frequency with a greater value of the periodic combined envelope sequence.

16. :

The decoding method according to claim 14,

wherein when an input indicator of the degree of periodicity is within a predetermined range indicating high periodicity, the variable-length decoding step decodes the variable-length code to obtain a frequency-domain sequence on the assumption that the amplitude of an audio signal is greater for a frequency with a greater value of the periodic combined envelope sequence; and

when the indicator is not within the predetermined range indicating high periodicity, the variable-length decoding step decodes the variable-length code to obtain a frequency-domain sequence on the assumption that the amplitude of an audio signal is greater for a frequency with a greater value of the spectral envelope sequence.