Long-term memory motion-compensated prediction

Long-term memory motion-compensated prediction extends the spatial displace ment vector utilized in block-based hybrid video coding by a variable time delay permitting the use of more frames than the previously decoded one for motion-compensated prediction. The long-term memory covers several seconds of decoded frames at the encoder and decoder. The use of multiple frames f or motion compensation in most cases provides significantly improved predic tion gain. The variable time delay has to be transmitted as side informatio n requiring an additional bit rate which may be prohibitive when the size o f the long-term memory becomes too large. Therefore, we control the bit rat e of the motion information by employing rate-constrained motion estimation . Simulation results are obtained by integrating long-term memory predictio n into an H.263 codec, Reconstruction PSNR improvements up to 2 dB for the Foreman sequence and 1.5 dB for the Mother-Daughter sequence are demonstrat ed in comparison to the TMN-2.0 H.263 coder. The PSNR improvements correspo nd to bit-rate savings up to 34 and 30 %, respectively. Mathematical inequa lities are used to speed up motion estimation while achieving full predicti on gain.