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

Abstract

With rapid progress in both computers and networks, real-time multimedia applications are now possible on the Internet. Since 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 the redundancy frame. We conducted user studies to experimentally measure 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 analyzed the system overhead incurred by the redundancy. We find that video redundancy can greatly improve the perceptual quality of video 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 primary frames alone.

Empirical evaluation of the congestion responsiveness of RealPlayer video streams

“…For these reasons, streaming video applications often use UDP as a transport protocol rather than TCP. Moreover, with the use of repair techniques [3], [18], [23], [24], UDP packet losses can be partially or fully concealed, reducing the impact of loss on the quality of the video by the user, and thus reducing the incentive for multimedia applications to lower their bitrate in the presence of packet loss during congestion.…”

Adjusting forward error correction with temporal scaling for TCP-friendly streaming MPEG

“…Previous work demonstrates the choice of temporal or quality scaling can, in fact, account for the content of the video being streamed [Tri-pathi and Claypool 2002]. Other potential areas of future work include extending our model to analyze other types of media repair, such as media-dependent FEC as in [Liu and Claypool 2000] and selective retransmissions as in [Feamster and Balakrishnan 2002].…”

“…This FEC pattern provides strong protection to each frame and roughly represents the relative importance of the I, P and B frames. For the MPEG settings in Table III, this adds approximately 15% overhead for each type of frame, which is typical for many fixed FEC approaches [Hardman et al 1995;Hartanto and Sirisena 1999;Liu and Claypool 2000]. (3) Adjusted FEC: Before transmitting, the sender uses the program described in Section 4.1 to determine the FEC and temporal scaling patterns that produce the maximum playable frame rate and uses these for the entire video transmission.…”

An empirical study of realvideo performance across the internet

“…Similarly, packet loss, a common measure of Internet performance, is not sufficient to characterize the performance of video traffic. While frame loss can have a severe impact on the perceptual quality of video, repair techniques to recover multimedia packet loss or ameliorate its effects [LC00,PHH98] are often applied to video streams.…”