Sum of Absolute Difference-based Rate-Distortion Optimization Cost Function for H.265/HEVC Intra-Mode Prediction

Abstract

The emerging standard of High Efficiency Video Coding (HEVC) provides a 50% improved compression performance compared to its predecessor H.264/AVC at the expense of increasing its computational complexity which is due to a large number of modes involved in the decision process where it would increase encoding time and provide hardware limitations. In this paper, the reduction of intra-coding complexity is proposed by utilization of Rate-Distortion Optimization (RDO) in preselecting a mode with the best RD cost, among all 35 intra-modes. Two cost functions – Sum of Absolute Difference (SAD) and Sum of Absolute Transform Difference (SATD, available in the HEVC Test Model (HM) Reference Software, are determined by making encoder decisions. This paper compares the performance and complexity cost of SAD only for intra-mode, with SATD-based intra-mode by modifying the HM reference encoder through forced selection of the mentioned modes. Results show that SAD consistently produces the least encoding time among all modes, along with sensible values of bitrate. Furthermore, error concealment was introduced in decoding the video sequences with the use of IEEE 802.22 Standard which only allowed power gains resulting to packet error rates (PER) ranging from 1% to 30% for the analysis on the behavior of each video sequence in an environment where error is introduced.