Motion compensated interpolation for very-low-bit-rate video applications

Recently, MPEG-4 has been formed to study very-low-bit-rate (VLBR) video coding for applications in videotelephony. In this thesis, we propose a possible postprocessing technique for VLBR system. In videophone applications, temporal subsampling is a common technique to be combined with other compression schemes to achieve very large compression ratio so as to satisfy the VLBR requirement. As a result, object motions tend to be jerky and disturbing to the human eyes. To smooth out object motions, we propose a postprocessing technique, motion compensated temporal interpolation (MCTI), to increase the instantaneous decoder frame rate. In MCTI, block-based exhaustive motion search is used to establish temporal association between two reconstructed frames. Both forward and backward searches are used to account for uncovered and newly covered areas properly. With MCTI, we show that one or more frames can be interpolated with acceptable visual quality. After showing the feasibility of MCTI, we propose a fast algorithm FMCTI with reduced computation requirement and acceptable visual quality. However, FMCTI generates blocking artifacts due to its sub-optimal property. A modified FMCTI (MFMCTI) is then proposed which can reduce the artifacts resulted from FMCTI