Optimized intra mode decision for high efficiency video coding

Abstract

In order to reach higher coding efficiency, the design of the newest video compression standard - High Efficiency Video Coding (HEVC) - is relying on many improved coding tools and sophisticated techniques. Such a complexity leads to the vital need of video encoders for fast algorithms to overcome the real-time encoding constraint and memory limits. In this context, we propose a gradient based pre-processing stage that will help decreasing the complexity of the encoder and will speed up the Intra mode decision. For that purpose, we investigate the potential of a Prewitt operator instead of the famous Sobel operator used to generate the gradient. In addition and in order to enhance the gradient potential of Intra mode detection without adding a significant complexity, we propose an optimized Intra mode selection through a neighbor mode extension as well as an adapted cost function to take into account the appearing number of modes and the gradient magnitudes. The obtained results demonstrate that we can reduce the encoding time for All Intra configuration by 31.9% with a loss in BD-rate of only 1.1%.