Hardware-Friendly Coding Unit Decision Scheme for HEVC

Quad-tree based coding unit partition in High-Efficiency Video Coding (HEVC) achieved significant coding efficiency improvements, but also brought increasing computational complexity. Especially, design challenges like data dependence, large area cost, and imbalance of processing time of each coding tree unit (CTU), make it hard to achieve a real-time structure for real-time hardware encoder for all CTU sizes. To solve these problems, we proposed a hardware-friendly fast CU decision scheme with multi-stage algorithms for HEVC hardware encoder, aiming at the most complex modules: IME (Integer Motion Estimation), FME/IP (Fractional Motion Estimation/ Intra Prediction), and MD (Mode Decision). Firstly, in IME stage, a zero block detection method based fast CU and PU decision algorithm was presented. Secondly, we presented an estimated RDO (Rate-Distortion Optimization) based algorithm in the Hadamard domain for the early CU decision further in FME/IP stage. Finally, under the condition of hardware computing time limitation of several CU sizes, we proposed a computation time constraint CU fast decision algorithm for MD stage. Experiments demonstrated that, compared with the original HM13.0 implementation, the proposed scheme achieved about 53.9% encoding time saving with merely 2.3% coding performance degradation. What's more, significant area cost and data dependency have been alleviated, which will be more hardware-friendly for HEVC encoder design.