Very low bit rate video coding using adaptive nonuniform sampling and matching pursuit

This thesis investigates motion-compensated, very low bit rate digital video compression. Specifically, it addresses the challenge of applying irregular sampling and matching pursuits to encode the motion compensation error, or residual, in a very low bit rate condition.; First, irregular sampling techniques are investigated and a set of basic extensions and improvement of the sampling process and restoration are developed. A new control weight function and restoration technique are developed. With an adaptive weight control function, Voronoi tessellation based irregular sampling generates a set of sampling locations that is highly correlated to the edge structure of the sampled image. This capability plays an important role in the development of the new hybrid residual coding technique.; The matching pursuit video coder is investigated next, and a basic extension of the dictionary searching algorithm is investigated. The matching pursuit video coder expands the motion residual on a larger, more flexible basis set than that of the classic block-DCT residual coder. Since such an overcomplete basis contains a wider variety of structures than the DCT basis, the motion residual can be represented more efficiently. A new hybrid residual coding technique based on matching pursuits and the Voronoi-based nonuniform sampling is developed. A new dictionary set has been revised and created.; Finally, the hybrid residual coding and motion estimation components are combined to build a video coder. The coder is used to investigate the performance of the new hybrid residual coding technique in a realistic setting. Experimental results suggest that our coder performance is comparable to that of the matching pursuit coder. The coder, however, clearly outperforms the standard H.263 coder. Decoded frames of our coder display significantly fewer blocking artifacts compared to DCT based coders. At the same time, our coder requires fewer computational operations in the dictionary searching process compared to the matching pursuit coder.