Affine multipicture motion-compensated prediction
Affine motion compensation is combined with long-term memory motion-compensated prediction. The idea is to determine several affine motion parameter sets on subareas of the image. Then, for each affine motion parameter set, a complete reference picture is warped and inserted into the multipicture buffer. Given the multipicture buffer of decoded pictures and affine warped versions thereof, block-based translational motion-compensated prediction and Lagrangian coder control are utilized. The affine motion parameters are transmitted as side information requiring additional bit rate. Hence, the utility of each reference picture and, with that, each affine motion parameter set is tested for its rate-distortion efficiency. The combination of affine and long-term memory motion-compensated prediction provides a highly efficient video compression scheme in terms of rate-distortion performance. The two incorporated multipicture concepts complement each other well providing almost additive rate-distortion gains. When warping the prior decoded picture, average bit-rate savings of 15% against TMN-10, the test model of ITU-T Recommendation H.263, are reported for the case that 20 warped reference pictures are used. When employing 20 warped reference pictures and 10 decoded reference pictures, average bit-rate savings of 24% can be obtained for a set of eight test sequences. These bit-rate savings correspond to gains in PSNR between 0.8-3 dB. For some cases, the combination of affine and long-term memory motion-compensated prediction provides more than additive gains.