A very low bit-rate video codec with optimal trade-off among DVF, DFD and segmentation

In this paper we present a theory for the optimal bit allocation among quad-tree (QT) segmentation, displacement vector field (DVF) and displaced frame difference (DFD). The theory is applicable to variable block size motion compensated video coders (VBSMCVC), where the variable block sizes are encoded using the QT structure, the DVF is encoded by first order differential pulse code modulation (DPCM), the DFD is encoded by a block based scheme and an additive distortion measure is employed. We consider the case of a lossless VBSMCVC first, for which we develop the optimal bit allocation algorithm using Dynamic Programming (DP). We then consider a lossy VBSMCVC, for which we use La-grangian relaxation and show how an iterative scheme, which employees the DP-based solution, can be used to find the optimal solution. We finally present a VBSMCVC, which is based on the proposed theory, which employees a DCT-based DFD encoding scheme. We compare the proposed coder with H.263. The results show that it outperforms H.263 by about 25% in terms of bit rate for the same quality reconstructed image.