Temporal image sequence prediction using motion field interpolation

摘要

A new method for motion-compensated temporal prediction of image sequences is proposed. Motion vector fields in natural scenes should possess two basic properties. First, the field should be smoothly varying within moving objects to compensate for nonrigid or rotational motion, and scaling of objects. Second, the field should be discontinuous along the boundaries of the objects. In the proposed method the motion vector field is modelled using finite element methods and interpolated using adaptive interpolators to satisfy the above-stated requirements. This is particularly important when only very sparse estimates of motion vector fields are available in the decoder due to bit-rate constraints limiting the amount of overhead information that can be transmitted. The proposed prediction method can be applied for low-bit-rate video coding in conventional codecs based on motion-compensated prediction and transform coding, as well as in model-based codecs. The performance of the proposed method is compared with standard motion-compensated prediction based on block matching. It is shown that for simple video telephony scenes a reduction of more than 30% in the energy of the prediction error can be achieved with an unchanged number of transmitted motion vectors and with only a modest increase in computational complexity. When implemented in an H.261 codec the new prediction method can improve the peak SNR 1–2 dB producing a significant visual improvement.