资料介绍
This paper proposes a new pitch prediction method for
4kbps CELP (Code Excited LpC) speech coding. In the
conventional CELP speech coding, synthetic speech quality
deteriorates rapidly at 4kbps, especially for female and
children’s speech with short pitch period. The important
reason is that when the pitch period is shorter than the
subframe length, simple repetition of the past excitation
signal based on the estimated lag, not the true pitch prediction,
is usually used in the adaptive codebook operation.
The proposed pitch prediction method can carry outthe true pitch prediction by utilizing the current subframe
excitation codevector signal, when the pitch prediction parameters
are determined. For further improvement, a split
weighting method and a low-complexity harmonic and spectral
perceptually-weighting method have also been developed.
The informal listening test result shows that the
4kbps coder with 20msec subframe, utilizing all of the proposed
improvements, achieves 0.2 MOS higher results than
the coder without them.
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