Weighted Multi-Hypothesis Inter Prediction for Video Coding

A key component of state-of-the art video coding is motion-compensated prediction, also called inter prediction. Current standards allow uni- and bi-prediction, i.e. linear superposition of up to two motion-compensated prediction signals. It is well-known that by a superposition of more than two prediction signals (or hypotheses), the energy of the prediction error can be further reduced. In this paper, it is shown that allowing the encoder to choose among different weights for the individual hypotheses is beneficial from a rate-distortion perspective. A practical multi-hypothesis inter prediction scheme based on the Versatile Video Coding Test Model (VTM) is presented. For VTM-1, in the Random Access configuration according to the JVET Common Test Conditions, the average luma BD bit rate is in the range of -1.6 % to -1.9 % for different settings using up to four prediction hypotheses. For VTM-2, the corresponding BD bit rate is -0.95 %. For higher bit rates (i.e., QP values 12, 17, 22, 27) the BD bit rates are -2.2 % for VTM-1 and -1.4 % for VTM-2.