Adaptive predictive coding with dynamic quantization adjustment (APC-DQA) at 16 kbits/s

An adaptive predictive coding with dynamic quantization adjustment(APC-DQA) is proposed for speech coding at 16 kbits/s, which aims to reduce processing delay and hardware complexity, while attaining "toll quality". The proposed scheme utilizes time-domain processing to lessen the processing delay. Moreover, it employs backward processing in both prediction and quantization, which requires less side information than forward processing. It also incorporates adaptive bit allocation in sub-intervals of each frame so as to remove redundancies due to periodic concentration of the prediction residual energy. The performance evaluation results show that the processing delay of the APC-DQA is 2/3 that of an adaptive predictive coding with adaptive bit allocation scheme (APC-AB) [1]. Moreover, its hardware complexity is approximately 70% to 80% of the APC-AB. It was also shown that this scheme can provide speech quality subjectively equivalent to 6.6 bit Log-PCM.