Fast adaptive inter-splitting decisions for HEVC based on luma residuals

The long encoding time of High Efficiency Video Coding (HEVC) compared to its predecessor, Advanced Video Coding (AVC), is mostly associated with the large number of Coding Units (CUs) to be processed during the quad tree splitting of the 64 × 64 Coding Tree Unit (CTU) along with the improved but intensive Motion Estimation (ME) techniques. In this paper, the unnecessary processing of some CUs during the recursive splitting of the CTU along with some of the two-PUs mode operations are skipped so as to bring significant time reduction for the encoder. Statistical distributions of the HEVC splitting decisions based on the Mean Square (MS) values of each 8 × 8 block within the 2N × 2N luma residuals are adaptively constructed during the starting frames for each sequence. Thereafter, thresholds for early termination of the CU and early identification of the 2N × 2N PU mode based on these distributions are applied during the encoding of subsequent inter frames. The proposed inter-mode scheme significantly reduces the total encoding time with negligible loss of coding efficiency. Experimental results show that the proposed scheme effectively achieves 47.0% encoding time savings with a Bjøntegaard Delta bitrate (BDBR) increase of only 0.57% for various test sequences under random access conditions.