Model based movement compensation and interpolation for ISDN videotelephony

Block matching is a very efficient technique for movement compensation in video codecs for low rates but has two main disadvantages: (1) integer displacements cause high-frequency artifacts at block borders in the estimated picture and (2) the block matching vectors are not suited for movement adaptive interpolation of skipped fields. Taking into account the generating process of the image sequence by central projection of a 3-D scene on a 2-D plane, these disadvantages can be avoided using object-matching techniques. Based on a movement model, a parameter vector can be calculated out of the measured block displacements. This parameter vector describes the noninteger displacement field of large areas without jumps at block borders. Computer simulations show a gain of 3 to 4 dB in signal-to-noise ratio of the reconstructed pictures compared with simple block matching. The application of the proposed approach to ISDN (integrated-services digital network) video telephony is considered