Recursive Partitioning Search Space Pruning Using Split Cost Prediction

One of the innovations in H.265/HEVC is the quad-tree partitioning framework. It allows flexible block subdivision and mode allocation across the encoded picture. The increased flexibility comes at a cost of vast search space expansion, making exhaustive search algorithms inapplicable. We propose a novel early termination condition to skip the exhaustive search of whole tree-branches in the well-established top-down encoding approach. The condition is based on a simple and intuitive split cost prediction. It can be parametrized to control the trade-off between the speed-up and caused BD-rate loss. Data driven parameter estimation and parameter number reduction is presented. For random-access encoding, the method can achieve an average speed-up of 30% with a BD-rate loss of 0.03%. At another trade-off point, speed-up is increased to over 40% for a BD-rate loss below 0.5%.