| With the rapid development of video coding techniques, especially after the occurrence of MPEG-4 and H.264/AVC, video compression rate has been improved a lot. On the other hand, the underlying networks (e.g. Internet, wireless, and etc.) have also been improved to support video transmitting. So more and more video applications over network come into use, e.g. Video on Demand, video conferencing, and video surveillance.However, the extremely high demand of video data still exceeds the ability of underlying Internet/wireless networks. Since most of the video applications don't allow too much delay, packets those carry video data often suffer from loss. The compressed video data are very sensitive to errors due to residues reduction. With no error control schemes, the decoded video often suffers from large quality degradation and causes visual artifacts. To reduce the effect of errors, a large number of error control schemes are induced both in video encoder and decoder.Wireless video transmission is expected to experience whole frame losses since data packets always carrying a whole frame in low-bitrate coding scenario.In this paper, a novel whole frame loss recovery scheme is proposed. Many algorithms have been developed, such as CAP,CAB and JMMV. These algorithms use the hypothesis that the motion between consecutive frames does not vary in a dramatic way. However, there are many cases that the motion varies frequently in consecutive frames. In the scheme proposed, A vector map Vmap for each frame is generated and encoded into the bitstream of the next frame. The Vmap contains useful information for decoder to recover the motion vector of the previous lost frame, and the content of Vmap is based on concealment modes, which are dynamically decided while encoding by estimating the motion variations through statistical analysis. The experimental results demonstrate the proposed scheme is very effective in dealing with the whole frame loss occurring on wireless video transmission. |
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