Method for speech coding, method for speech decoding and their apparatuses

• US 8,688,439 B2
• Filed: 03/11/2013
• Issued: 04/01/2014
• Est. Priority Date: 12/24/1997
• Status: Expired due to Fees

• Current Assignee: Blackberry Limited
• Original Assignee: Blackberry Limited
• Inventors: Yamaura, Tadashi
• Primary Examiner(s): Azad, Abdul
• Application Number:
  US13/792,508
• Publication Number:
  US 20130204615A1
• Time in Patent Office: 386 Days
• Field of Search: 704219-230
• US Class Current: 704/225
• CPC Class Codes: G10L 13/02 Methods for producing synthetic speech; Speech synthesisers
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• 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 19/083 the excitation function being an excitation gain G10L25/90 takes precedence
• 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 19/107 Sparse pulse excitation, e.g. by using algebraic codebook
• 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 19/125 Pitch excitation, e.g. pitch synchronous innovation CELP [PSI-CELP]
• CPC Class Codes: G10L 19/135 Vector sum excited linear prediction [VSELP]
• CPC Class Codes: G10L 19/18 Vocoders using multiple modes
• CPC Class Codes: G10L 2019/0002 Codebook adaptations
• CPC Class Codes: G10L 2019/0005 Multi-stage vector quantisation
• CPC Class Codes: G10L 2019/0007 Codebook element generation
• CPC Class Codes: G10L 2019/0011 Long term prediction filters, i.e. pitch estimation
• CPC Class Codes: G10L 2019/0012 Smoothing of parameters of the decoder interpolation
• CPC Class Codes: G10L 2019/0016 Codebook for LPC parameters
• CPC Class Codes: G10L 21/0264 characterised by the type of parameter measurement, e.g. correlation techniques, zero crossing techniques or predictive techniques
• CPC Class Codes: G10L 25/93 Discriminating between voiced and unvoiced parts of speech signals G10L25/90 takes precedence

Abstract

A high quality speech is reproduced with a small data amount in speech coding and decoding for performing compression coding and decoding of a speech signal to a digital signal. Ina speech coding method according to a code-excited linear prediction (CELP) speech coding, a noise level of a speech in a concerning coding period is evaluated by using a code or coding result of at least one of spectrum information, power information, and pitch information, and various excitation code books are used based on an evaluation result.

Claims

1. A speech decoding method for an apparatus having a decoder, the method comprising:

receiving, by the decoder, a coded speech signal including a gain code;

decoding, by the decoder, a gain from the gain code;

obtaining a time series vector with a number of samples with zero amplitude-value from an excitation codebook;

modifying the time series vector based on the decoded gain such that the number of samples with zero amplitude-value is changed; and

synthesizing a speech signal based on the modified time series vector.

2. The method of claim 1, further comprising:

obtaining an adaptive code vector from an adaptive codebook based on an adaptive code associated with the coded speech signal.

3. The method of claim 2, further comprising:

weighting the adaptive code vector and the modified time series vector; and

adding together the weighted adaptive code vector and the weighted time series vector.

4. The method of claim 3, further comprising:

decoding a linear prediction parameter from a linear prediction parameter code associated with the coded speech signal; and

synthesizing the speech signal using the linear prediction parameter and the added weighted adaptive code vector and weighted time series vector.

5. The method of claim 4, wherein the decoded linear prediction parameter corresponds to coefficients of a synthesis filter.

6. The method of claim 2, wherein the gain is decoded in a decoding period corresponding to the coded speech signal.

7. The method of claim 2, wherein the adaptive codebook is based on a past excitation.

8. The method of claim 1, further comprising:

weighting an adaptive code vector and the modified time series vector; and

adding together the weighted adaptive code vector and the weighted time series vector.

9. The method of claim 8, further comprising:

decoding a linear prediction parameter from a linear prediction parameter code associated with the coded speech signal; and

synthesizing the speech signal using the linear prediction parameter and the added weighted adaptive code vector and weighted time series vector.

10. The method of claim 1, wherein the time series vector is modified based on a noise level.

11. A speech decoding apparatus having a decoder configured to:

receive, by the decoder, a coded speech signal including a gain code;

decode, by the decoder, a gain from the gain code;

obtain a time series vector with a number of samples with zero amplitude-value from an excitation codebook;

modify the time series vector based on the decoded gain such that the number of samples with zero amplitude-value is changed; and

synthesize a speech signal based on the modified time series vector.

12. The apparatus of claim 11, further configured to:

obtain an adaptive code vector from an adaptive codebook based on an adaptive code associated with the coded speech signal.

13. The apparatus of claim 12, further configured to:

weight the adaptive code vector and the modified time series vector; and

add together the weighted adaptive code vector and the weighted time series vector.

14. The apparatus of claim 13, further configured to:

decode a linear prediction parameter from a linear prediction parameter code associated with the coded speech signal; and

synthesize the speech signal using the linear prediction parameter and the added weighted adaptive code vector and weighted time series vector.

15. The apparatus of claim 14, wherein the decoded linear prediction parameter corresponds to coefficients of a synthesis filter.

16. The apparatus of claim 12, wherein the gain is decoded in a decoding period corresponding to the coded speech signal.

17. The apparatus of claim 12, wherein the adaptive codebook is based on a past excitation.

18. The apparatus of claim 11, further configured to:

weight an adaptive code vector and the modified time series vector; and

add together the weighted adaptive code vector and the weighted time series vector.

19. The apparatus of claim 18, further configured to:

decode a linear prediction parameter from a linear prediction parameter code associated with the coded speech signal; and

synthesize the speech signal using the linear prediction parameter and the added weighted adaptive code vector and weighted time series vector.

20. The apparatus of claim 11, wherein the time series vector is modified based on a noise level.