<title>Using redundancy to repair video damaged by network data loss</title>

With rapid progress in both computers and networks, real- time multimedia applications are now possible on the Internet. Sine the Internet was designed to support traditional applications, multimedia applications on the Internet often suffer from unacceptable delay, jitter and data loss. Among these, data loss often has the largest impact on quality. In this paper, we propose a new forward error correction technique for video that compensates for lost packets, while maintaining minimal delay. Our approach transmits a small, low-quality redundant frame after each full-quality primary frame. In the event the primary frame is lost, we display the low-quality frame, rather than display the previous frame or retransmit the primary frame. To evaluate our approach, we simulated the effect of network data loss on MPEG video clips and repaired the data loss by using redundancy frames. We conducted user studies that experimentally measured users' opinions on the quality of the video streams in the presence of data loss, both with and without our redundancy approach. In addition, we analyze the system overhead incurred by the redundancy. We find that video redundancy can greatly improve the perceptual quality of video in the presence of network data loss. The system overhead that redundancy introduces is dependent on the quality of the redundant frames, but a typical redundancy overhead will be approximately 10% that of the original frames.