Efficient H.264-to-HEVC Transcoding Based on Motion Propagation and Post-Order Traversal of Coding Tree Units

Abstract

In this paper, we propose a fast H.264-to-HEVC transcoder composed of a motion propagation algorithm and a fast mode decision framework. The motion propagation algorithm creates a motion vector candidate list at the coding tree unit (CTU) level and, thereafter, selects the best candidate at the prediction unit level. This method eliminates computational redundancy by pre-computing the prediction error of each candidate at the CTU level and reusing the information for various partition sizes. The fast mode decision framework is based on a post-order traversal of the CTU, and includes several mode reduction techniques. In particular, the framework permits the early termination of the rate distortion cost computation, a highly complex task, when a mode is unpromising. Moreover, a novel method exploits the data created by the motion propagation algorithm to determine whether a coding unit (CU) must be split. This allows the pruning of unpromising sub-partitions. Compared to a cascaded pixel-domain transcoding approach, the experimental results show that the proposed solution using one reference frame is on average 8.5 times faster, for an average BD-Rate of 2.63%. For a configuration with 4 reference frames, the average speed-up is 11.77x and the average BD-Rate is 3.82%.

Efficient HEVC-to-VVC Transcoder Based On A Bayesian Classifier For The First Quadtree Depth Level

“…of heterogeneous transcoders has been of great relevance in the literature. On the one hand, there are fast transcoders between standards such as the one proposed by J.-F. Franche and S. Coulombe in 2018 [4]. This H.264-to-HEVC transcoder can speed up the coding time by 11.77× with a penalty of 3.82% in terms of the Bjøntegaard delta rate (BD-rate) [5].…”