Efficient prediction of CU depth and PU mode for fast HEVC encoding using statistical analysis

• We propose a fast algorithm with both CU size and PU mode decision method for HEVC.
• All of the 13 neighboring CTUs are analyzed to predict the current CU depth.
• k-means method is used to classify the neighboring CTUs into different groups.
• PU mode candidates are selected according to the CU depth.
• The proposed method gets 56.71% and 59.76% time reduction with LP and RA profiles.

High Efficiency Video Coding (HEVC) adopts complex quadtree-structured CU (coding unit) and PU (prediction unit) modes. Thus, the search process for optimal modes causes high computational complexity in HEVC. To solve this problem, a fast coding algorithm is proposed. Thirteen neighboring CTUs (Coding Tree Unit) are divided into three classes with the k-means method, and are selectively used as the reference CTUs to calculate the predicted CU depth levels for the current CTU. Additionally, for every CU depth, we skip some rarely used PU modes to reduce the complexity of the PU selection algorithm. Experimental results show that compared with the HEVC reference software, our algorithm can achieve 56.71% time saving with Low Delay Configuration profile and 59.76% with Random Access Configuration profile, whereas values of BDBR (Bjontegaard Delta Bit Rate) are only 1.0517% and 0.9918%, respectively. Compared with five state-of-the-art algorithms, the proposed algorithm has significant encoding time reduction with good bitrate performances.