This paper proposes a fast search method of algebraic codebook in CELP coders. In the proposed method, the sequence of codebook search is reordered according to the criterion of mean squared weighted error between tar...
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ISBN:
(纸本)0780350413
This paper proposes a fast search method of algebraic codebook in CELP coders. In the proposed method, the sequence of codebook search is reordered according to the criterion of mean squared weighted error between target vector and filtered adaptive codebook vector, and the algebraic codebook is searched until a predetermined threshold is satisfied. This method reduces the computations considerably compared with G.729 at the expense of a slight degradation of speech quality. Moreover, it gives better speech quality with smaller average search space than G.729A.
This paper proposes a new 4 kbit/s speech coder based on CELP structure with 45 ms total codec delay. The coder is mainly featured by the renewal codebook of the excitation signal and the linked split-vector quantizer...
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ISBN:
(纸本)0818679190
This paper proposes a new 4 kbit/s speech coder based on CELP structure with 45 ms total codec delay. The coder is mainly featured by the renewal codebook of the excitation signal and the linked split-vector quantizer of line spectrum pair parameters which enable the coder to get high quality speech at low bit rate. In addition, techniques of formant enhancement in the spectral envelop and harmonic recovery in the transient region are also introduced to reduce buzzy and hoarse sounds, respectively. From the intensive listening test with intermediated response system (IRS) speech, we obtained a comparable subjective quality to 32 kbit/s ADPCM (ITU Recommendation G.726) under a nominal speech input level of -26 dB overload.
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