| Video conference system is a kind of multi-media communication technology. People can use it to meet with others on network. End-point is the important segment in video conference system, and video codec is the core. In this paper, a thorough study is carried out over the key algorithms of distortion constrained video codec, several optimization methods are proposed to enhance the coding speed and promote the applications of video coding in actual practice.Because of all of above, Xi'an government has certificated this project and given us enough support.In this paper, the theory and implementing method of software VLBR video encoder based on the ITU-T H.263 low-bit rate video coding standard are studied deeply in order to satisfy the demand of narrow-band video communication or multimedia communication. Based on baseline H.263 video coding, many refined coding methods, such as Improved PB-frames and Advanced Intra Coding, and so on, are discussed to improve the coding efficiency and to optimize video encoder. Generally, the high efficient coding methods are more complex and time-consuming, so some methods are introduced to speed up, such as MMX technology adopted in DCT and motion estimation. According to the experimental results of computer simulation and the tradeoff between reconstructed picture quality and coding speed, the optimized scheme of VLBR encoder is proposed. |
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