Error spreading: reducing bursty errors in continuous media streaming

With the growing popularity of the Internet, there is increasing interest in using it for audio and video transmission. Periodic network overloads, leading to bursty packet losses, have always been a key problem for network researchers. In a long-haul, heterogeneous network like the Internet, handling such an error becomes especially difficult. Perceptual studies of audio and video viewing have shown that bursty losses have the most annoying effect on people, and hence are critical issues to be addressed for applications such as Internet phone, video conferencing, distance learning, etc. Classical error handling techniques have focused on applications like FTP, and are geared towards ensuring that the transmission is correct, with no attention to timeliness. For isochronous traffic like audio and video, timeliness is a key criterion, and given the high degree of content redundancy, some loss of content is quite acceptable. We introduce the concept of error spreading, which is a transformation technique that takes the input sequence of packets (from an audio or video stream) and scrambles its packets before transmission. The packets are unscrambled at the receiving end. The transformation is designed to ensure that bursty losses in the transformed domain get spread all over the sequence in the original domain. Perceptual studies have shown that users are much more tolerant of a uniformly distributed loss of low magnitude. We next describe a continuous media transmission protocol based on this idea, and validate its performance through an experiment performed on the Internet.