| With the development of information technology in 21st century, the communication contents do not only have simple aural and literal information, and we also hope to be provided indubitable, intuitionistic and effective visual information. With the popularization of wireless communication manufactures, such as high mobile phone and PDA, it is hotplot to develop video codec. But the digital video and audio is too huge to be stored and transmitted. As one of the multimedia compression and coding standards, MPEG4 plays an important role in multimedia field. Due to its object-based idea, it has the virtues of high compression ratio, scalability, interactivity with users and so on.Based on the research background of mobile communication, with roundly understanding the MPEG4 standard, we research the core algorithms of the MPEG4 video coding and optimize the DCT and motion estimation.Firstly, we use two algorithms to optimize DCT. We used binDCT which is implemented using only binary shift and addition operations to decrease the complexity. And another algorithm is content-depended fast DCT called partial coefficients DCT. For low bit-rate video coders, most of the blocks are represented only a few non-zero coefficients. So we can compare SAD with a threshold to decide which blocks can use partial DCT.Secondly, we use a fast block-matching algorithm named normalized partial distortion search is proposed. The proposed algorithm reduces computations by using a halfway-stop technique in the calculation of block... |
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