Intra Prediction Strategies for Lossless Compression in High Efficiency Video Coding

Abstract

HEVC, an abbreviation for high efficiency video coding, is a digital coding standard for videos developed by the JCT-VC committee to address the bandwidth and storage space requirements, associated while handling the high definition multimedia content. Sophisticated coding tools and mechanisms are deployed into the framework making it far more superior to its predecessor standard H.264 both in terms of compression efficiency and quality of reconstruction, but at the cost of increased complexity. This thesis is mainly based on the sample-based intra prediction strategies to improve the prediction accuracy that results in the enhancement of the compression efficiency, for the lossless mode of HEVC. Lossless coding becomes imperative in certain applications like video analytics, video surveillance, etc., that mandate distortion-free data reconstruction. The main focus of the thesis is to mitigate the spatial redundancy persistent due to coherence, smoothness, illumination and shadowing effects in the natural video sequences. These issues can also challenge another class of multimedia content commonly referred to as the screen content (SC) sequences as a result of certain peculiarities which they exhibit. Therefore, the prediction generation stage of the CODEC plays a significant role in an attempt to minimize the entropy using the superior intra prediction strategies. The gradient dependent predictor, context-based predictor, and the improvised blend of predictors which is based on the penalizing factor modify the intra prediction mechanisms of HEVC to emerge as the highlight of this thesis. The overall algorithmic performance is evaluated by deriving the savings in bit-rate and run-time. Additionally, the comparisons made with the several state-of-the-art prediction techniques reveal that significant improvements in coding gains with reasonable computational complexity and at par savings in run-time is attained using the proposed methods. The algorithmic modifications are embedded into the HEVC reference software provided by the JCT-VC and its validation is performed using the HEVC test sequences along with another class of natural sequences referred to as the Class 4K