Region-based subband coding of image sequences

This thesis presents a region-based subband video coding scheme for coding of arbitrarily shaped regions. Specifically, it addresses the issues of subband decomposition of arbitrarily shaped regions, source modeling for efficient coding of texture regions, rate-constrained motion estimation, and coding of motion compensation error for arbitrarily shaped regions.; Shape adaptive subband decomposition methods for subband decomposition of arbitrarily shaped regions are developed. The treatment of arbitrary length signals for 2-D separable sub-band decomposition is discussed in detail. Signal extension methods as well as filtering algorithms that preserve the number of samples of the input signal in the subband domain while maintaining the spatial locality, correlation, perfect reconstruction, and self-similarity across subbands are presented. Equivalent convolution-based and lifting-based implementations are also presented.; The statistical distribution of the subband signals are modeled by multivariate, specifically bivariate, generalized Gaussian (GG) distribution functions. Parametrized bivariate GG models allow efficient adaptation to the changing statistical characteristics of video signals. The bivariate GG distribution model can capture nonlinear higher order relationships that exist between adjacent signal elements in the subband domain. Using these models, efficient 2-D quantizers and entropy codes are designed. These distribution functions are also used for predicting the rate-distortion characteristics of the subbands. Bit allocation among subbands is based on these rate-distortion characteristics.; A fast exhaustive search algorithm for rate-constrained motion estimation is presented. The motion vectors are selected from a search window based on a rate-distortion criterion by successively eliminating the search positions depending on the rate constraint. The estimation performance of the proposed algorithm is identical to the performance of the rate-constrained full search algorithm, with considerable reduction in computation.; A region-based hybrid video coding scheme is developed by combining the SA subband decomposition, rate-constrained motion estimation, shape coding, and residual coding components. The encoding and decoding processes are described. The performance of the coder is compared to the performance of an existing video coding standard.