| Due to the development of the communication, traditional data and voice telecommunication is gradually developing to the video communication. At present, the video communication mainly carries on the wired network. Such as digital television service carries on cable TV network, videophone service carries on public switched telephone network(PSTN), videoconference system carries on integrated services digital network(ISDN) or IP network.The wireless communication gets rid of the fetter of wired, which will become an important means for free communication. With the rapid development of wireless technology and video compression technology, video communication is going to carry on the wireless network. However, Video signal is big and has high real-time and high bit error rate request. On the other hand, wireless channel is band-limited, multipath-flatting, high-error-rate. This implies the need to develop techniques for video signal and wireless channel.In this paper, we study three key technologies in the wide-band wireless video network. They are MPEG-4, Turbo codes and OFDM. Firstly, we introduce MPEG-4 standard and analyse its coding core thought and coding process, we achieve the MPEG-4 SP codec by using VC++6.0. Then, we compare H.263 encoder, MPEG-2 MP encoder and MPEG-4 SP encoder in low bit-rate condition and the result shows that MPEG-4 SP encoder has better performance.Secondly, we introduce the structure of Turbo encoder and decoder and derive the formula of MAP algorithm and its modified algorithms in the log domain (including Max-Log-MAP and Log-MAP). Then, we compare the performance of... |
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