| With the continuous development of the wireless network, multimedia as a carrierof information has become the main way to communicate, more and more mobile videoterminal equipments are used for multimedia communications. Due to the limitedprocessing capability and power consumption of these devices, the conventional videoencoding standards like MPEG and H.264having high degree of complexity at theencoder are no longer applicable to the applications above.Based on this background, the distributed video coding gain widespread attentionwith its unique advantages. Distributed Video Coding using independent encoding andjoint decoding, combining channel coding techniques, has characteristics of lowcomplexity, low power consumption at the encoder and good robustness etc.In the DVCwith feedback channel, the decoder is the key factor affecting the system performance.This article has a deep study and analysis of LDPC decoding algorithm, the virtualchannel model, side information generating and updating algorithm at the decoder. Onthis basis, the paper first proposes a side information updating algorithm based onvirtual channel model. This algorithm using the correlation between WZ frame and sideinformation constantly updates undecoded bit planes on the basis of the decoded bitplane within the same coefficient band to get better side information. The correlationbetween WZ frame and side information can be represented by correlated noise. Thegreater correlated noise is, the weaker the correlation is, on the contrary, the smallercorrelated noise is, the stronger the correlation is, performing on the LDPC decoding,the parity bits need to be transmitted are less. The algorithm improves side informationby reducing the correlated noise, thus obtaining better compression performance bystrengthening the correlation between the two. Then, based on the side informationupdating algorithm, the paper proposes the LDPC decode updating algorithm. Thisalgorithm adjusts the initial likelihood ratio and values of the variable node during theiterative decoding process on the purpose of reducing the number of parity bits beingtranmitted and improving the compression ratio.Experimental results show that theproposed algorithms improve the overall rate distortion performance by1-2dB. |
