We propose a method of providing error resilient H.264 video over 802.11 wireless channels by using a feedback mechanism which does not incur an additional delay typically found in ARQ-type feedback. Our system uses the TCP/IP and UDP/IP protocols, located between the medium access control (MAC) layer of 802.11, and the H.264 video application layer. The UDP protocol is used to transfer time sensitive video data without delay; however, packet losses introduce excessive artifacts which propagate to subsequent frames. Error resilience is achieved by a feedback mechanism-the decoder conveys the packet-loss information as small TCP packets to the video source as negative acknowledgements. By using multiple reference frames, slice-based coding and timely intra-refresh, the encoder makes use of this feedback information to perform subsequent temporal prediction without propagating the error to future frames. We take static measurements of the actual channel and use the packet loss and delay patterns to test our algorithms. Simulations show an improvement of 0.5~5 dB in PSNR over plain UDP-based video transmission. Our method improves the overall quality of service of interactive video transmission over wireless LAN; it can be used as a model for future media-aware wireless network protocol designs.
|Translated title of the contribution||Error-resilient low-delay H.264/802.11 transmission via cross-layer coding with feedback channel|
|Title of host publication||Visual Communications and Image Processing 2005, Beijing, China|
|Publisher||Society of Photo-Optical Instrumentation Engineers (SPIE)|
|Pages||1 - 12|
|Number of pages||12|
|Publication status||Published - 12 Jul 2005|