| With 3G and the convergence of wired and wireless networks, the mobile video services for either fixed or mobile terminals are attracting more and more attention. However, its enabling technologies are still in the researching stage, one of the difficulties among which is the method of fast channel switching. Compared to switching time of 300ms in traditional TV, the long delay of mobile video switching will not satisfy the users' requirements, and will limit services' spreading and innovation. So, it's significant to reduce the switching delay of mobile video services for their furthermore applications.First, the feature of mobile video services and the significance of fast channel switch are introduced. In the following, the channel switching time in mobile environment is analyzed, in which the time of waiting for reference frames is identified as the main part. After researching on current methods of reducing channel switching time, a novel scheme of switching frames insertion, based on SP/SI frames of H.264, is proposed. That is to say, by inserting the switching frames properly, the time of waiting for reference frames, namely the major time of the channel switching time, can be reduced. By utilizing JM software, simulations are conducted to validate and evaluate the scheme proposed, such as bitrate and PSNR, waiting time of reference frames in error or errorless. The results show that by the scheme, the channel switch time for mobile video services can be decreased effectively. At last, under MBMS, two innovative schemes based on audience ratings and frames insertion or layered encoding are proposed.This paper innovates in the following fields:1. Analyzes the channel switch time in mobile environment, points out that the time of waiting reference frames is the main part; 2. Based on SP/SI frames of H.264, a novel scheme of switching frames insertion is proposed, which can reduce the major time of the channel switch time, and simulations are conducted by JM software;3. Under MBMS architecture, raises two innovative schemes based on audience ratings and frames insertion or layered encoding, which can realize fast channel switch and be used in different situations. |
