Gradient-based fast decision for intra prediction in HEVC

As the next generation standard of video coding, the High Efficiency Video Coding(HEVC) achieves significantly better coding efficiency than all existing video coding standards, which is however at the cost of a much higher computation complexity. To address this issue, this paper presents a gradient-based fast decision algorithm for intra prediction in HEVC. More specifically, the intra prediction in HEVC is divided into two stages: prediction unit(PU) size decision and mode decision. At the PU size decision process, four orientation features are extracted from the coding unit by the intensity gradient filters to decide the texture complexity and texture direction of the coding unit, and then the texture direction is used to exclude impossible prediction modes at the mode decision process. Compared to HEVC reference software, the proposed algorithm saves around 56.7% of the encoding time in intra high efficiency setting and up to 70.86% in intra low complexity setting with slight performance degradation.