Error-resilient mobile video by edge adapted multiscale transforms

Summary form only given, as follows. Mobile video systems face particularly challenging problems due to the hostile nature of the mobile radio channel and the very low bit-rate available. For the fading channel, the Shannon separation principle does not hold, and hence source and channel coding should be considered jointly. This talk reviews some advances in our work on joint optimization of video coding and error control schemes for the mobile radio channel. As a new formal framework for end-to-end optimization, the so-called distortion-distortion-function (DDF) is introduced that shows the distortions introduced by source coding vs. the distortions resulting from channel errors for varying bit allocation between source and channel coding. We show the impact of various error-resiliency techniques on the DDF, such as motion-compensated concealment, increasing the frequency of synchronization words in the bit-stream, or increasing the percentage of intra-coded blocks. We show that for increasing burstiness of channel errors, the importance of an error-resilient decoder increases, while the effectiveness of FEC decreases. Channel-adaptive source coding is shown to be a powerful technique, if channel feedback can be incorporated into the source coder. Finally we address techniques that take advantage of layered scalable representations of the video signal. In order to achieve unequal error protection of the layers, we discuss FEC across IP packets and receiver-driven adaptive pre-etching techniques. Such techniques can be advantageously combined with proxy servers for mobile multimedia access