Method for speech coding, method for speech decoding and their apparatuses
View Patent ↗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.
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.