Martyn J. Riley

Varying slice size to improve error tolerance of MPEG video

Video data encoded using the Motion Picture Experts Group (MPEG) standards is highly susceptible to errors during transmission or storage. We investigate whether the error tolerance of coded MPEG video can be improved by varying the size of each slice depending on the class of coded picture. We evaluate the effect of varying the slice size within each of the three MPEG picture classes on the error tolerance of the coded sequence. We encode a number of test sequences and subject each one to simulated transmission errors. We show that reducing the slice size in I and P pictures improves the decoded quality in the presence of errors. The slice size in B pictures can be increased without significantly reducing the tolerance to errors. Reducing the slice size in I and P pictures whilst increasing the slice size in B pictures can significantly improve the tolerance of the coded sequence to transmission errors without increasing the amount of coded data. A video sequence encoded in this way complies with the MPEG1 and MPEG2 standards.

Usage parameter control cell loss effects on MPEG video

The effect of the ATM network usage parameter control function on VBR coded MPEG video is investigated. A video sequence is coded using MPEG and packetised into ATM cells. A simulated generic rate control algorithm (GRCA) function monitors the stream of cells and cells which exceed the connection parameters are dropped. The effect of these lost cells on the decoded video data is evaluated. Cells lost in this way severely degrade the quality of the decoded video data. We conclude that it is important to avoid UPC cell loss effects on video traffic.

Improving the error tolerance of MPEG video by varying slice size

Abstract The error tolerance of video data encoded using the MPEG standards can be improved by varying the size of each slice depending on the class of coded picture. We investigate the effect of varying slice size within each of the three MPEG picture coding classes on the error tolerance of the coded MPEG bitstream. By reducing the slice size in coded I and P pictures and increasing the slice size in coded B pictures it is possible to significantly improve the error tolerance of coded MPEG video without increasing the amount of transmitted data.

FEC and mutli-layer video coding for ATM networks

Significant advances have been made in recent years on standards [1][2][3] for video compression. Compressed video data resulting from these coding standards is however susceptible to quality degradation when cell losses occur during transmission over an ATM network.

An Optimised Implementation of Reed-Solomon FEC on the PC

Communication protocols for the PC such as the Internet transport protocol (TCP) have traditionally made use of ARQ techniques to perform error correction for data transmission applications. ARQ is not however a suitable error correction technique for real-time communications and especially for the transmission of compressed video traffic over networks with a high bandwidth-delay product. A number of International Standards are available for video compression including the ITU-T H.261 and emerging H.263 standards aimed at providing video conferencing at bit rates of n x 64 Kbit/s and below. Compressed video traffic is extremely sensitive to data loss during transmission [1] and many communication systems do not provide the relatively high Quality of Service required for digital video communications. In these circumstances error correction must be performed in the end systems and FEC is a more suitable technique than ARQ.