Method and apparatus for speech encoding by evaluating a noise level based on pitch information
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorTadashi Yamaura
Life of this patent
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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. In 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 codebooks are used based on an evaluation result.
Claims2
A speech encoding method for encoding a speech according to code-excited linear prediction (CELP) comprising:
- analyzing the speech to obtain a linear prediction parameter;
- obtaining a linear prediction parameter code by encoding the linear prediction parameter;
- obtaining an adaptive code vector concerning an adaptive code from an adaptive codebook;
- obtaining pitch information corresponding to the adaptive code;
- evaluating a noise level of the speech based on the pitch information, wherein the evaluated noise level indicates how close the speech is to unvoiced speech;
- obtaining a weight based on the evaluated noise level;
- obtaining an excitation code by comparing a coded speech and the speech, wherein the coded speech is obtained by using the adaptive code vector and an excitation code vector, the excitation code vector being obtained by adding a plurality of time series vectors, wherein at least one of the time series vectors is weighted by the weight;
- and
- outputting a speech code including the adaptive code, the linear prediction parameter code, and the excitation code.
A speech encoding apparatus for encoding a speech according to code-excited linear prediction (CELP) comprising:
- an analyzing unit for analyzing the speech to obtain a linear prediction parameter;
- a linear prediction parameter code obtaining unit for obtaining a linear prediction parameter code by encoding the linear prediction parameter;
- an adaptive code vector obtaining unit for obtaining an adaptive code vector concerning an adaptive code from an adaptive codebook;
- a pitch information obtaining unit for obtaining pitch information corresponding to the adaptive code;
- an evaluating unit for evaluating a noise level of the speech based on the pitch information, wherein the evaluated noise level indicates how close the speech is to unvoiced speech;
- a weight obtaining unit for obtaining a weight based on the evaluated noise level;
- an excitation code obtaining unit for obtaining an excitation code by comparing a coded speech and the speech, wherein the coded speech is obtained by using the adaptive code vector and an excitation code vector, the excitation code vector being obtained by adding a plurality of time series vectors, wherein at least one of the time series vectors is weighted by the weight;
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- an outputting unit for outputting a speech code including the adaptive code, the linear prediction parameter code, and the excitation code.
Dependencies are inferred from the claim text.