Differential motion vector coding for scalable coding
Deepak S. Turaga, Mihaela van der Schaar, Béatrice Pesquet‐Popescu · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2003
Motion compensated wavelet video coding provides very high coding efficiency while enabling spatio-temporal-SNR-complexity scalability. Besides the high degree of adaptabitility, the inherent data prioritization leads to increased robustness in conjunction with unequal error protection (UEP) schemes, and improved error concealment. Hence, motion compensated wavelet video coding schemes are generating great interest for wireless video streaming. Such schemes use motion compensated temporal filtering (MCTF) to remove temporal redundancy. Many extensions to conventional MCTF schemes, that increase the flexibility and the coding efficiency, have been proposed. However these extensions require the coding of additional sets of motion vectors. In this paper, we first define a redundancy factor to identify the additional number of motion vectors that need to be coded with such schemes. We then propose to exploit the temporal correlations between motion vectors to code and estimate them efficiently. We use prediction to reduce the bits needed to code motion vectors. We describe two prediction methods, and highlight the advantages of each scheme. We also use MV prediction during motion estimation, i.e. change the search center and the search range based on the prediction, and describe the tradeoffs to be made between rate, distortion, and complexity. We perform several experiments to illustrate the gains of using temporal prediction, and identify the content dependent nature of results.