Semi-fixed-length motion vector coding for H.263-based low bit rate video compression

We present a semi-fixed-length motion vector coding method for H.263-based low bit rate video compression. The method exploits structural constraints within the motion field. The motion vectors are encoded using semi-fixed-le ngth codes, yielding essentially the same levels of rate-distortion perform ance and subjective quality achieved by H.263's Huffman-based variable leng th codes in a noiseless environment. However, such codes provide substantia lly higher error resilience in a noisy environment.