WYNER-ZIV VIDEO CODING BASED ON TURBO CODES EXPLOITING PERFECT KNOWLEDGE OF PARITY BITS

摘要

In a Wyner-Ziv video coding system based on turbo codes, parity bits are generated for a Wyner-Ziv frame and transmitted to the decoder. In this context of distributed source coding, we can assume that the transmission of the parity bits is guaranteed to be error-free by the lower network layers. In our work, we propose a simple method to exploit the guaranteed reliability of the parity bits so that the turbo decoding achieves a better performance. The proposed scheme is to assign the parity bits a higher weight than the information bits in turbo decoding. Our simulation on binary sequences shows that the proposed scheme enables turbo codes to come closer to the Slepian-Wolf bound in distributed lossless source coding. When it is applied to Wyner-Ziv video coding, the bit rate is reduced by 2%-4% for a given video quality. Although the gain is relatively small, it comes for free, because all that we have to do is to multiply the parity bits with a sufficiently large factor before the decoding process starts.