Scalable motion vector coding
Recently proposed scalable wavelet-based video codecs using spatial-domain motion compensated temporal filtering (SDMCTF) offer competitive compression performance when compared to H.264 and generate embedded bit-streams supporting quality, resolution and temporal scalability. To be able to support a large range of bit-rates with optimal compression efficiency, these codecs require a quality-scalable motion vector coding technique. Such an algorithm based on the integer wavelet transform followed by embedded coding of the wavelet coefficients was proposed in the recent past. In this paper, we present a quality-scalable motion vector coding algorithm using median-based motion vector prediction. The compression performance of the proposed algorithm is compared to that of the wavelet-based technique and is found to be superior. Additionally, the proposed motion vector codec is incorporated into an SDMCTF-based video codec and the benefits of using quality-scalable motion vector representations are experimentally demonstrated.