MDC With Its Conditional Pdf-based Bi-direction Predicting Quantization

With the rapid development of internet and mobile network, multimedia application are gradually recognized as popular services specially, real-time transmission over error-prone channel has become the hot topic of researches. Multiple Description Coding (MDC) is an effective fault-tolerant technology of signal transmission, due to low-latency requirements and random time-varying characteristics of voice communications, Multiple Description Speech Coding (MDSC) is a great challenge in MDC research.Considering the difficulties of multiple description coding, we propose the Bi-direction Predicting Quantization (BDPQ) algorithm that takes advantage of interleaving and parameter interpolation. Furthermore BDPQ is employed to create a MD-CWI codec. The main work includes:1. BDPQ algorithm is proposed. Pitch and power factor of the target frame are quantized by the information of previous and next frames, then copy the quantized codeword to descriptions. Experiments demonstrate that MDC based on BDPQ algorithm achieves better error concealment performance than parameter interpolation algorithm.2. Modify the CW reconstruction method. We suggest a new method which uses pitch to restore CW phase spectrum, and combines phase spectrum with amplitude spectrum in CW reconstruction process. The proposed method achieves a better PESQ than the traditional method.3. Based on BDPQ algorithm and the interpolation feasibility of various parameters in CWI, we realize the MD-CWI codec. Compared to SD-CWI, MD-CWI gets average 0.96 increase of PESQ under various random packet loss rates and 0.81 increase of PESQ under various burst packet loss rates.