H.264/AVC影像傳輸其錯誤回復與失真式錯誤保護之研究

Abstract

Recent research efforts on distributed video coding and Wyner-Ziv problems have revealed an exciting, new possibility for video applications. The Wyner-Ziv coding paradigm has suggested a novel protection scheme that can effectively combat packet losses. In this thesis, we investigate the application of lossy error protection for H.264/AVC video streaming over wireless network. Video waveforms are protected using the Wyner-Ziv coding concept, resulting in graceful video quality degradation in the presence of increasing network error rate. In addition, we propose a feedback-based network adaptation algorithm to dynamically optimize the performance of error protection in the presence of changing network dynamics. In our design, we have applied the systematic error protection framework to the baseline H.264/AVC video stream. The systematic portion consists of unprotected video bitstream. At the same time, the Wyner-Ziv encoder generates the second, coarser representation of the unprotected, original video bitstream at much lower rate than the original. Then, the Wyner-Ziv decoder utilized the side information from the video decoder to reconstruct the coarse video waveform. When network packets are lost, the erroneous video frame can be recovered by the coarse video waveform. As a result, the video distortion caused by network packet loss is bounded by the Wyner-Ziv description. The Wyner-Ziv decoder also sends feedback messages to the Wyner-Ziv encoder; then the Wyner-Ziv encoder can adapt to varying network condition and achieve graceful video quality degradation. Based on our experimental results, we have shown that lossy error protection can provide acceptable, eye-pleasing video quality over a large range of packet loss rates. When combining with our network adaptation algorithm, we have shown that the lossy error protection scheme can be further enhanced to provide smooth quality adaptation for H.264/AVC video transmission over wireless network.