Multiple-reference-picture video coding using polynomial motion models
Thomas Wiegand, Eckehard G. Steinbach, Axel Stensrud, Bernd Girod · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1998
We present a new video coding scheme that uses several references frames for improved motion-compensated prediction. The reference pictures are warped versions of the previously decoded frame applying polynomial motion compensation. In contrast to global motion compensation, where typically one motion model is transmitted, we show that in the general case more than one motion model is of benefit in terms of coding efficiency. In order to determine the multiple motion models we employ a robust clustering method based on the iterative application of the least median of squares estimator. The approach is incorporated into an H-263-based video codec and embedded into a rate- constrained motion estimation and macroblock mode decision frame work. It is demonstrated that adaptive multiple reference picture coding in general improves rate-distortion performance. PSNR gains of 1.2 dB in comparison to the H-263 codec for the high global and local motion sequence Stefan and 1 dB for the sequence Mobile and Calendar, which contains no global motion, are reported. These PSNR gains correspond to bit-rate savings of 21 percent and 30 percent comparing to the H-263 codec, respectively. The average number of motion models selected by the encoder for our test sequences is between 1 and 7 depending on the actual bit- rate.