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Wyner-Ziv video coding : adaptive rate control, key frame encoding and correlation noise classification

Abstract

Wyner Ziv (WZ) video coding is based on the results of the Slepian-Wolf and Wyner-Ziv theorems where the temporal correlation between neighboring frames is exploited at the decoder. This approach enables designing low-cost, low complexity encoders which are essential for some recent applications such as video surveillance and mobile camera phone. Despite recent advances in WZ video coding, the rate distortion performance is still far from that of predictive coding. One of the main factors affecting the WZ coding performance is the accuracy of modeling the dependency (correlation noise) between a frame to be coded and its estimation (side information) at the decoder. In existing transform domain Wyner-Ziv video coding methods, blocks within a frame are treated uniformly to estimate the correlation noise even though the success of generating side information is different for each block. This thesis proposes a method to estimate the correlation noise by differentiating blocks within a frame based on the accuracy of the side information. A second contribution of this dissertation is exploiting the temporal correlation between key frames which are usually simply intra coded. We propose a frequency band coding mode selection for key frames to exploit similarities between adjacent key frames at the decoder to improve the overall performance. Furthermore, the advantage of applying both schemes in a hierarchical order is investigated. Rate control is an important issue in many video applications. In Wyner-Ziv video coding architectures, the available bit budget for each GOP is shared between key frames and Wyner-Ziv frames. In this dissertation, we propose a model to express the relationship between the quantization step size of key and WZ frames based on their motion activity. Then we apply this model to propose an adaptive algorithm adjusting the quantization step size of key and WZ frames to achieve and maintain a target bit rate. The objective and subjective quality of the proposed method is evaluated

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