| 摘要 |
PROBLEM TO BE SOLVED: To improve the quantization efficiency at a low bit rate. SOLUTION: A linear predictive reverse filter obtains the residue signal of an input voice, the residue signal is segmented by a pitch cycle and shifted in phase into PW so that the correlation with a reference pulse becomes large, and the PW is made cyclic in pitch cycles (15); and an impulse response is convoluted in the output (16) to obtain a target waveform, a PW code vector is selected from a code book 17 and given a gain, and then one pitch cycle is segmented (19); and impulse response is convoluted in the output (22) to obtain a composite waveform, and the code vector and gain that minimize the square of the error between the composite waveform and target waveform are determined. |
