Optimized Intra Mode Decision for High Efficiency Video Coding

Abstract

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%.

Fast Mode Decision Technique for HEVC Intra Prediction Based on Reliability Metric for Motion Vectors

“…In particular, Refs. [11]- [13] first calculate the pixel-wise gradient direction, which is converted into the corresponding angular mode, and then select a small set of candidates for the RMD based on a histogram analysis for the pixel-wise angular modes [11], [12], or a kernel density estimation approach [13]. The other gradient-based techniques [14]- [16] first estimate a rough gradient direction among 0…”

Gradient-based pre-processing for intra prediction in High Efficiency Video Coding

“…Such a work is motivated by the fact that Prewitt operator offers simpler coefficients that can contribute much less implementation complexity for a gradient solution. In [23], we have conducted a motivation work using the Prewitt operator with granular pixel coverage, toward further understanding the gradient operators' impact on HEVC video coding. We also presented a pixel neighbor extension of the gradient values in order to enhance the performance of the intra mode detection.…”

“…We also presented a pixel neighbor extension of the gradient values in order to enhance the performance of the intra mode detection. In [24], we investigated the two-dimensional Roberts operator to even more simplify the gradient computation. In addition, we considered the appearance number of modes, as well as the gradient magnitude in order to optimize the performance of intra mode detection.…”