Efficient spatio-temporal segmentation for very low bit rate video coding

The goal of low bit rate video coding is:to minimise the number of bits which are required to represent a video sequence whilst maintaining an acceptable level of reconstructed image quality. Most of the conventional video coding schemes remove spatial and temporal redundancy by using block based motion compensation and transform coding such as DCT. However the disadvantage of these techniques is that blocking artefacts occur at high compression ratios due to the fact that the block structures are not adapted to the image contents. In ellis paper an efficient joint spatio-temporal segmentation scheme is proposed to segment and represent image contents based on the spatial characteristics and motion vectors. Two spatio-temporal segmentation algorithms have been proposed. The first uses arbitrarily shaped regions and the other an efficient quad-tree structure which is well suited to very low bit rate video coding. The experimental results show that the proposed scheme produced significant improvements in both objective and subjective quality at low bit rates when compared with fixed block-size segmentation.