| The traditional video coding standards, such as MPEG-x or the H.26x recommendations, rely on the encoder to exploit the statistics of the source signal. So the encoder is typically 5 to 10 times more complex than the decoder. In recent years, the emerging applications, such as wireless sensor network, mobile camera phones, and wireless video surveillance systems, have a significant impact on our lives. It breeds challenge to the coding structure characterized by a significantly lower complex encoder and a higher complex video decoder. However, distributed video coding is ideally meeting this requirement.The information-theoretic bases of distributed video coding were established in the 1970s by Slepian and Wolf for distributed lossless coding and by Wyner and Ziv for lossy coding. Compared to the traditional codec, a dramatic change is shifting the majority of complexity to the decoder. The major task of exploiting the source redundancy is partially or wholly placed at the decoder.The main contributions and innovation points of the thesis are as follows:1.On analysis of the characters of intra mode selection, integer transform and quantization, an efficient algorithm is proposed to detect all-zero blocks of the encoding intra frame in H.264. In the proposed method, dynamic selection of the threshold is used to examine the all-zero blocks in order to avoid the integer transform and quantization. Compared with the previous methods, the maximum percent of the all zero-blocks detected by the proposed algorithm in the intra macroblocks is 87.8%. It provides significant improvement of coding speed and can meet the needs of the video communication in real time.2.An improved algorithm is proposed for the side information generation process. For the blocks with low motion, the side information is interpolated by bi-directional motion compensation. For other blocks, it is replaced by a candidate block from the key frame which has minimum border error with four adjacent blocks. And the Markov random field (MRF)-Maximum a Posteriori (MAP) is used to smooth the blocks with high border error to the adjacent blocks. Simulations results show the proposed scheme can achieve 0.28 dB gains on PSNR with declining bitrate.3.A skip mode is introduced in the Wyner-Ziv frame coding process, as well as a theoretical analysis on the benefits of the block partition to the coding efficiency. The skip mode decision is introduced at the decoder on a block-by-block basis. In the proposed scheme, a mode decision process is performed to determine whether to apply skip mode to the blocks with low motion first. With the skip-mode, the block is reconstructed from the side information in the decoder. In addition, the non-skip mode blocks are divided into two parts by motion activity. The encoding bitplane is extracted within each set and encoded independently. Simulations show the proposed scheme can achieve up to 54.29% bitrate savings without visible PSNR sacrifice.4.With a comparison on a few rate estimation algorithms, a proposed algorithm for the bi-directional distributed video coding codec is proposed in the thesis. The proposed algorithm estimates the rate of each bitplane with the side information and the Laplacian distribution of difference between the source and the side information. And the result is transmitted to the encoder via a feedback channel. The simulation result indicates that the algorithm shows an efficient improvement in the precision of rate. And the complexity of the decoder is further declined.All of the proposed algorithms in this thesis are simulated and examined, then compared with conventional schemes in order to prove their validities and advantages.
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