A novel VLC encoding algorithm with high performance of symbol synchronization

The variable-length codes (VLCs) are very sensitive to errors, usually one bit error will cause incorrectly decoded symbols in succession. This error propagation effect makes the symbol error probability 2 to 3 orders of magnitude higher than the original bit error probability. In video communication, error propagation effect leads to that the reconstructed video perceptive quality can not be accepted even when the original bit error-probability is less than 10. In this paper, we propose a novel VLC encoding algorithm, called AVLC, which employs two types of VLC codes to encode the source symbols alternately. The maximum aposteriori probability (MAP) decoding algorithm is used when errors occurred We have obtained very good results that, under Gauss or BSC channel with bit-error probability about 10/sup -3/ the error propagation effect can be avoided effectively without any channel coding protection. This algorithm provides an effective way to guarantee the reliability of data communication, especially the video communication, against the background of high noise.