Error robust video coding based on H.263

In wireless communication transmission errors will occur, and if compressed digital video is used, the compression algorithm has to be error robust. This paper discusses a new technique for error robust video coding based on H.263. It consists of two parts. Firstly, the reference frame, with respect to which the differential frames are coded, is not the previous frame, but a frame composed of a set of N previous reconstructed frames at the decoder. This will smooth the error and as a result the visual quality improves substantially. Secondly, at the decoder an algorithm is implemented for the detection of errors in the frame to be displayed. The positions of the corrupted macro blocks that are detected are signaled to the encoder. When the encoder receives this information, it forces intra coding of the macro blocks at these positions in some future frame, depending on the delay. This is not the same as re-transmission, since only the coding mode (intra) of some future macro block at a certain spatial position is requested. Experiments show significant improvement in error robustness and resulting quality while maintaining the same bit rate. At a bit error rate (BER) of 10^-4 an improvement of 13.8 dB (PSNR) was obtained and maintained during the whole test sequence