Projection-based time-varying subband image coding

A novel time-varying subband transform with projection-based reconstruction and its application in image coding are introduced. At each time instance (block), the transform to be applied is chosen from a given set of orthogonal subband transforms according to a certain criterion. The reconstruction from the transformed coefficients is possible by applying the theory of convex projections (POCS). We introduce convex sets for perfect reconstruction from the transformed vector. We further propose other convex sets which assure smoothness of plane regions in the decoded image. Experimental results show that the use of multiple subband transforms leads to the improvement of coding performance compared to the use of single transform.