Scalable video compression using longer motion compensated temporal filters

Three-dimensional (3-D) subband/wavelet coding using a motion compensated temporal filter (MCTF) is emerging as a very effective structure for highly scalable video coding. Most previous work has used two-tap Haar filters for the temporal analysis/synthesis. To make better use of the temporal redundancies, we are proposing an MCTF scheme based on longer biorthogonal filters. We show a lifting based coder capable of subpixel accurate motion compensation. If we retain the fixed size GOP structure of the Haar filter MCTFs, we need to use symmetric extensions at both ends of the GOP. This gives rise to loss of coding efficiency at the GOP boundaries resulting in significant PSNR drops there. This performance can be considerably improved by using a 'sliding window,' in place of the GOP block. We employ the 5/3 filter and its non-orthogonality causes PSNR variation, which can be reduced by employing filter-based weighting coefficients. Overall the longer filters have a higher coding gain than the Haar filters and show significant improvement in average PSNR at high bit rates. However, a doubling in the number of motion vectors to be transmitted, translates to a drop in PSNR at the lower video bit rates.