Gradient-Based Fast Intra Coding Decision Algorithm for HEVC

The video coding standard, High efficiency Video Coding (HEVC), has come into view in these years. Compared with H.264/AVC, it can improve the performance by up to 50% bitrate saving. However, it also leads to a high encoding complexity. In order to decrease the complexity, we propose a new fast CU size decision and mode decision algorithm for HEVC intra coding. In particular, aiming at CU size decision, a joint method for classification and early termination is proposed according to gradient map and threshold function. In the process of mode decision, the number of checked intra prediction modes (IPM) is decreased based on multiple texture directions. Compared with the HEVC reference software HM 16.9, the proposed algorithm can save approximately 33.76% encoding time on average, which has better performance in time-saving than recent algorithms with slightly loss of BD-Rate.