声码器基音周期参数抗差错算法

Error correction scheme for vocoder pitch

为降低在窄带高误码率信道上语音传输的失真,针对基音参数提出了一种解码端抗差错算法。语音信号的基音周期本身变化比较平缓,在解码端将当前语音帧的基音参数与上一帧的基音参数进行比较,若发现变化超过一定范围,则认为是当前帧基音参数出错,并对其进行纠错处理。为了防止由于基音参数的重建错误而引起的误码扩散,若上一帧语音进行过纠错处理,则当前帧语音不作纠错处理,直到下一帧语音再跳入恢复算法。实验结果表明:在1%以上的随机误码率下,采用本文提出的纠错算法后,信道误码引起的声码器基音参数误差能够降低10%以上。

A pitch error resilience scheme was developed to reduce speech distortion through narrow band channels with high bit-error-rates. Natural speech pitch changes slowly, so the pitch in the current frame can be compared with the pitch in the previous frame in the decoder. If the variation exceeds some range, the pitch in the current frame will be assumed to be erroneous and corrected. Error propagation due to erroneous pitch restoration can be avoided by delaying the restoration scheme until the next frame if the previous frame was also determined to be erroneous and was restored. Tests show, the modified restoration scheme can reduce the pitch error due to channel errors at least 10% on channels with bit-error-rates above 1%.