Towards efficient wavefront parallel encoding of HEVC: Parallelism analysis and improvement

High Efficiency Video Coding (HEVC) is the new generation video coding standard which achieves significant improvement in coding efficiency. Although HEVC is promising in many applications, the increased computational complexity is a serious problem, which makes parallelization necessary in HEVC encoding. To better understand the bottleneck of parallelization and improve the encoding speed, in this paper, we propose a Coding Tree Blocks (CTB) level parallelism analysis method as well as a novel Inter-Frame Wavefront (IFW) parallel encoding method. First, by establishing the relationship between parallelism and dependence, parallelism is precisely described by CTB-level dependence as a criterion to evaluate different parallel methods of HEVC. On this basis, by effectively decreasing the dependence based on Wavefront Parallel Processing (WPP), IFW method is developed. Finally, with the proposed parallelism analysis method, IFW is theoretically proved to be of higher parallelism compared with other HEVC representative parallel methods. Extensive experimental results show that, the proposed method and implementation can bring up to 17.81x, 14.34x and 24.40x speedup for HEVC encoding of WVGA, 720p and 1080p standard test sequences with the same ignorable coding performance degradation as WPP, thus showing a promising technology for future large-scale HEVC video application.