Sound encoding apparatus and method, and sound decoding apparatus and method

• US 7,680,669 B2
• Filed: 03/07/2002
• Issued: 03/16/2010
• Est. Priority Date: 03/07/2001
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Ozawa, Kazunori
• Primary Examiner(s): Dorvil; Richemond
• Assistant Examiner(s): GODBOLD, DOUGLAS
• Application Number:
  US10/469,923
• Publication Number:
  US 20040117178A1
• Time in Patent Office: 2,931 Days
• Field of Search: 704/219, 704/220, 704500-504
• US Class Current: 704/500
• CPC Class Codes: G10L 19/10 the excitation function being a multipulse excitation
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
• CPC Class Codes: G10L 2019/0005 Multi-stage vector quantisation
• CPC Class Codes: H03M 7/3082 Vector coding for television signals, see H04N19/94

Abstract

A plurality of sets of position code books indicating the pulse position are provided in a multi-set position code book storing circuit (450). In accordance with a pitch prediction signal obtained in an adaptive code book circuit (500), one type of position code book is selected from the plurality of position code books in a position code book selecting circuit (510). From the selected position code book, a position is selected by a sound source quantization circuit (350) so as to minimize distortion of a sound signal. An output of the adaptive code book circuit (500) and an output of the sound source quantization circuit (350) are transferred.

Thus, a sound signal can be encoded while suppressing deterioration of the sound quality with a small amount of calculations even when the encoding bit rate is low.

Claims

1. A sound encoding apparatus having spectral parameter calculating means for receiving a sound signal and calculating a spectral parameter, spectral parameter quantizing means for quantizing the spectral parameter calculated by said parameter calculating means and outputting the quantized spectral parameter, impulse response calculating means for converting the output spectral parameter from said spectral parameter quantizing means into an impulse response, adaptive code book means for obtaining a delay and gain from a past quantized sound source signal on the basis of an adaptive code book to predict a sound signal and obtain a residual signal, and outputting the delay and gain, a sound source signal of the sound signal being represented by a combination of pulses having non-zero amplitudes, and sound source quantizing means for quantizing the sound source signal and gain of the sound signal by using the impulse response, and outputting the quantized sound source signal and gain, comprising:

position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

position code book selecting means for selecting one type of code book from said plurality of types of position code books on the basis of at least one of the delay and gain of said adaptive code book,

said sound source quantizing means calculating a distortion of the sound signal by using the impulse pulse response for each of all combinations of positions that a plurality of pulses contained in the thus selected position code book can take respectively, and quantizing a pulse position by selecting a combination of positions at which the distortion is decreased; and

multiplexer means for combining an output from said spectral parameter quantizing means, an output from said adaptive code book means, and an output from said sound source quantizing means, and outputting the combination.

2. The sound encoding apparatus according to claim 1, wherein said position code books all contain identical pulses in common.

3. The sound encoding apparatus according to claim 1, wherein said sound source quantizing means calculates said distortion of the sound signal for each of all combinations of the positions that the plurality of pulses contained in the selected position code book can take respectively and the respective pulse code vectors stored in a sound source code book, and selects such a combination of a position and a polar code vector that decreases said distortion.

4. A sound encoding apparatus having spectral parameter calculating means for receiving a sound signal and calculating a spectral parameter, spectral parameter quantizing means for quantizing the spectral parameter calculated by said parameter calculating means and outputting the quantized spectral parameter, impulse response calculating means for converting the output spectral parameter from said spectral parameter quantizing means into an impulse response, adaptive code book means for obtaining a delay and gain from a past quantized sound source signal on the basis of an adaptive code book to predict a sound signal and obtain a residual signal, and outputting the delay and gain, a sound source signal of the sound signal being represented by a combination of pulses having non-zero amplitudes, and sound source quantizing means for quantizing the sound source signal and gain of the sound signal by using the impulse response, and outputting the quantized sound source signal and gain, comprising:

position code book storing means for storing a plurality of types of position code books each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse position that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

position code book selecting means for selecting one type of code book from said plurality of types of position code books on the basis of at least one of the delay and gain of said adaptive code book,

said sound quantizing means calculating a distortion of the sound signal by using the impulse response for each of all combinations of positions that a plurality of pulses contained in the thus selected position code book can take respectively, selecting a combination of positions at which the distortion is decreased, reading out a gain code vector stored in a gain code book for each position in the thus selected combination of positions to quantize the gain to thereby recalculate said distortion of the sound signal, and selectively outputting one type of combination of a position and gain code vector by which the distortion is decreased; and

multiplexer means for combining an output from said spectral parameter quantizing means, an output from said adaptive code book means, and an output from said sound source quantizing means, and outputting the combination.

5. A sound encoding apparatus having spectral parameter calculating means for receiving a sound signal and calculating a spectral parameter, spectral parameter quantizing means for quantizing the spectral parameter calculated by said parameter calculating means and outputting the quantized spectral parameter, impulse response calculating means for converting the output spectral parameter from said spectral parameter quantizing means into an impulse response, adaptive code book means for obtaining a delay and gain from a past quantized sound source signal on the basis of an adaptive code book to predict a sound signal and obtain a residual signal, and outputting the delay and gain, a sound source signal of the sound signal being represented by a combination of pulses having non-zero amplitudes, and sound source quantizing means for quantizing the sound source signal and gain of the sound signal by using the impulse response, and outputting the quantized sound source signal and gain, comprising:

position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of a said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

discriminating means for extracting a feature from the sound signal and discriminating and outputting a mode;

position code book selecting means for selecting one type of code book from said plurality of types of position code books on the basis of at least one of the delay and gain of said adaptive code book, if an output from said discriminating means is a predetermined mode,

said sound source quantizing means calculating a distortion of the sound signal by using the impulse response for each of all combinations of positions that a plurality of pulses contained in the thus selected position code book can take respectively,

said sound source quantizing means calculating distortion of the sound signal by using the impulse response with respect to a position stored in the selected code bookif the output from said discriminating means is the predetermined mode, and quantizing a pulse position by selected a combination of positions at which the distortion is decreased; and

multiplexer means for combining an output from said spectral parameter quantizing means, an output from said adaptive code book means, an output from said sound source quantizing means, and the output from said discriminating means, and outputting the combination.

6. A sound decoding apparatus comprising:

demultiplexer means for receiving a code concerning a spectral parameter, a code concerning an adaptive code book, a code concerning a sound source signal, and a code representing a gain, and demultiplexing these codes;

adaptive code vector generating means for generating an adaptive code vector by using the code concerning an adaptive code book;

position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

position code book selecting means for selecting one type of code book from said plurality of types of position code books on the basis of at least one of a delay and gain of said adaptive code book;

sound source signal restoring means for generating a pulse having a non-zero amplitude with respect to the position code book selected by said code book selecting means by using the codes concerning a code book and sound source signal, and generating the sound source signal by multiplying the pulse by a gain by using the code representing the gain; and

synthetic filter means formed by a spectral parameter to receive the sound source signal and output a reproduction signal.

7. A sound decoding apparatus comprising:

demultiplexer means for receiving a code concerning a spectral parameter, a code concerning an adaptive code book, a code concerning a sound source signal, a code representing a gain, and a code representing a mode, and demultiplexing these codes;

adaptive code vector generating means for generating an adaptive code vector by using the code concerning an adaptive code book, if the code representing the mode is a predetermined mode;

position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

position code book selecting means for selecting one type of code book from said plurality of types of position code books on the basis of at least one of a delay and gain of said adaptive code book, if the code representing the mode is the predetermined mode;

sound source signal restoring means for generating, if the code representing the mode is the predetermined mode, a pulse having a non-zero amplitude with respect to the position code book selected by said code book selecting means by using the codes concerning a code book and sound source signal, and generating a sound source signal by multiplying the pulse by a gain by using the code representing the gain; and

synthetic filter means formed by a spectral parameter to receive the sound source signal and output a reproduction signal.

8. A sound encoding method having the spectral parameter calculation step of receiving a sound signal and calculating a spectral parameter, the spectral parameter quantization step of quantizing and outputting the spectral parameter, the impulse response calculation step of converting the quantized spectral parameter into an impulse response, the adaptive code book step of obtaining a delay and gain from a past quantized sound source signal on the basis of an adaptive code book to predict a sound signal and obtain a residual signal, and outputting the delay and gain, a sound source signal of the sound signal being represented by a combination of pulses having non-zero amplitudes, and the sound source quantization step of quantizing the sound source signal and gain of the sound signal by using the impulse response, and outputting the quantized sound source signal and gain, comprising:

preparing position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

the position code book selection step of selecting one type of code book from the plurality of types of position code books on the basis of at least one of the delay and gain of the adaptive code book;

the step of calculating a distortion of the sound signal by using the impulse response for each of all combinations of positions that a plurality of pulses contained in the thus selected position code book can take respectively, and quantizing a pulse position by selected a combination of positions at which the distortion is decreased in the sound source quantization step; and

the multiplexing step of combining an output from the spectral parameter quantization step, an output from the adaptive code book step, and an output from the sound source quantization step, and outputting the combination.

9. The sound encoding method according to claim 8, wherein said position code books all contain identical pulses in common.

10. The sound encoding method according to claim 8, wherein said sound source quantizing means calculates said distortion of the sound signal for each of all combinations of the positions that the plurality of pulses contained in the selected position code book can take respectively and the respective pulse code vectors stored in a sound source code book, and selects such a combination of a position and a polar code vector that decreases said distortion.

11. A sound encoding method having the spectral parameter calculation step of receiving a sound signal and calculating a spectral parameter, the spectral parameter quantization step of quantizing and outputting the spectral parameter, the impulse response calculation step of converting the quantized spectral parameter into an impulse response, the adaptive code book step of obtaining a delay and gain from a past quantized sound source signal on the basis of an adaptive code book to predict a sound signal and obtain a residual signal, and outputting the delay and gain, a sound source signal of the sound signal being represented by a combination of pulses having non-zero amplitudes, and the sound source quantization step of quantizing the sound source signal and gain of the sound signal by using the impulse response, and outputting the quantized sound source signal and gain, comprising:

preparing position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

the position code book selection step of selecting one type of code book from the plurality of types of position code books on the basis of at least one of the delay and gain of the adaptive code book;

the step of reading out a gain code vector stored in a gain code book for each position stored in the position code book selected in the position code book selection step, quantizing a gain to calculate distortion of the sound signal, and selectively outputting one type combination of a position and gain code vector by which the distortion is decreased, in the sound source quantization step; and

the multiplexing step of combining an output from the spectral parameter quantization step, an output from the adaptive code book step, and an output from the sound source quantization step, and outputting the combination,

wherein said sound source quantizing step further comprises;

calculating a distortion of the sound signal by using the impulse response for each of all combinations of positions that a plurality of pulses contained in the thus selected position code book can take respectively, selecting a combination of positions at which the distortion is decreased, reading out a gain code vector stored in a gain code book for each position in the thus selected combination of positions to quantize the gain to thereby recalculate said distortion of the sound signal, and selectively outputting one type of combination of a position and gain code vector by which the distortion is decreased.

12. A sound encoding method having the spectral parameter calculation step of receiving a sound signal and calculating a spectral parameter, the spectral parameter quantization step of quantizing and outputting the spectral parameter, the impulse response calculation step of converting the quantized spectral parameter into an impulse response, the adaptive code book step of obtaining a delay and gain from a past quantized sound source signal on the basis of an adaptive code book to predict a sound signal and obtain a residual signal, and outputting the delay and gain, a sound source signal of the sound signal being represented by a combination of pulses having non-zero amplitudes, and the sound source quantization step of quantizing the sound source signal and gain of the sound signal by using the impulse response, and outputting the quantized sound source signal and gain, comprising:

preparing position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

the discrimination step of extracting a feature from the sound signal and discriminating and outputting a mode;

the position code book selection step of selecting one type of code book from the plurality of types of position code books on the basis of at least one of the delay and gain of the adaptive code book, if an output from the discrimination step is a predetermined mode;

for each of all combinations of positions that a plurality of pulses contained in the thus selected position code book can take respectively, if the output from the discrimination step is the predetermined mode, and quantizing a pulse position by selecting a combination of positions at which the distortion is decreased, in the sound source quantization step; and

the multiplexing step of combining an output from the spectral parameter quantization step, an output from the adaptive code book step, an output from the sound source quantization step, and the output from the discrimination step, and outputting the combination.

13. A sound decoding method comprising:

the demultiplexing step of receiving a code concerning a spectral parameter, a code concerning an adaptive code book, a code concerning a sound source signal, and a code representing a gain, and demultiplexing these codes;

the adaptive code vector generation step of generating an adaptive code vector by using the code concerning an adaptive code book;

preparing position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

the position code book selection step of selecting one type of code book from the plurality of sets of position code books on the basis of at least one of a delay and gain of the adaptive code book;

the sound source signal restoration step of generating a pulse having a non-zero amplitude with respect to the position code book selected in the code book selection step by using the codes concerning a code book and sound source signal, and generating a sound source signal by multiplying the pulse by a gain by using the code representing the gain; and

the synthetic filtering step formed by a spectral parameter to receive the sound source signal and output a reproduction signal.

14. A sound decoding method comprising:

the demultiplexing step of receiving a code concerning a spectral parameter, a code concerning an adaptive code book, a code concerning a sound source signal, a code representing a gain, and a code representing a mode, and demultiplexing these codes;

the adaptive code vector generation step of generating an adaptive code vector by using the code concerning an adaptive code book, if the code representing the mode is a predetermined mode;

preparing position code book storing means for storing a plurality of types of position code books, each containing an identical set of pulse positions, each of said types of position code books providing a different association of a plurality of said pulses with a subset of pulse positions within said identical set of pulse positions that is different from associations between said pulses and said subsets of pulse positions in the remaining types of position code books;

the position code book selection step of selecting one type of code book from the plurality of sets of position code books on the basis of at least one of a delay and gain of the adaptive code book, if the code representing the mode is the predetermined mode;

the sound source signal restoration step of generating, if the code representing the mode is the predetermined mode, a pulse having a non-zero amplitude with respect to the position code book selected in the code book selection step by using the codes concerning a code book and sound source signal, and generating a sound source signal by multiplying the pulse by a gain by using the code representing the gain; and

the synthetic filtering step formed by a spectral parameter to receive the sound source signal and output a reproduction signal.