MPEGII Video Coding For Noisy Channels

This thesis considers the performance of MPEG-II compressed video when transmitted over noisy channels, a subject of relevance to digital terrestrial television, video communication and mobile digital video. Results of bit sensitivity and resynchronisation sensitivity measurements are presented and techniques proposed for substantially improving the resilience of MPEG-II to transmission errors without the addition of any extra redundancy into the bitstream. It is errors in variable length encoded data which are found to cause the greatest artifacts as errors in these data can cause loss of bitstream synchronisation. The concept of a ‘black box transcoder’ is developed where MPEG-II is losslessly transcoded into a different structure for transmission. Bitstream resynchronisation is achieved using a technique known as error-resilient entropy coding (EREC). The error-resilience of differentially coded information is then improved by replacing the standard 1D-DPCM with a more resilient hierarchical pyramid predictor. The transmission of MPEG-II is considered over three different channels; a channel subject to random bit errors, a channel subject to burst errors and an ATM link subject to cell losses. Finally strategies for concealing lost image portions are considered and techniques are presented for recovering corrupted sequences when no black box transcoder has been used.