Robust H.263 compatible video transmission for mobile access to video servers

For interactive video storage applications that retrieve video data over low bit-rate networks, precoded bit-streams have to be transmitted to the receiver with low latency. Besides random access, fast forward and reverse, the scalability of the bit-stream is an important requirement for the above application. In this paper, we investigate a standard compatible approach that avoids the overhead involved in the transmission of periodic I-frames. We propose to store multiple bit-streams of different rates at the video server, which can be selected for transmission. Especially encoded P-frames are used to switch between the stored bit-streams. During normal-speed playback only P-frames are transmitted, providing increased efficiency. The approach is evaluated in the framework of the H.263 video compression standard. Based on the Salesman test sequence encoded at 12.5 fps in QCIF format, the resulting frame jitter is investigated when an error control protocol is used to transmit the bit-streams over a wireless DECT channel. Compared to periodic I-frames at an interval of 800 ms, a gain of 2 dB PSNR can be observed at the same frame jitter