Abstract:The recent High Efficiency Video Coding (HEVC) standard was designed to achieve significantly improved compression performance compared to the widely used H.264/AVC standard. This achievement was motivated by the ever-increasing popularity of high-definition video applications and the emergence of ultra-HD. Unfortunately, this comes at the expense of a significant increase in computational complexity for both inter and intra coding. To alleviate this problem, in this paper, we propose a fast intra mode decision method based on improved edge detection, consideration of most relevant modes from neighboring blocks, and classification of SATD costs permitting the elimination of several candidate modes prior to rate distortion optimization (RDO). Experimental results show that the proposed method provides time reduction up to 39.2% and an average 35.6% with negligible quality loss as compared to the HEVC reference implementation HM 15.0.

High efficiency video coding (HEVC) increases the number of intra coding modes to 35 to provide higher coding efficiency than previous video coding standards. This results in an increased encoder complexity, since there are more modes to be processed by the high resource-demanding rate-distortion optimization (RDO). In this paper, we propose a novel method to reduce the HEVC intra mode decision computational complexity and encoding time. This method is based on the prediction of the RDO cost of intra modes from a low-complexity sum of absolute transformed differences-based cost. By predicting the RDO cost, we are able to exclude non-promising modes from further processing and thereby save substantial computations. Also, a gradient-based method, using the Prewitt operator, is proposed to eliminate the non-relevant directional modes from the list of candidates. For even more complexity reduction, a mode classification is proposed to adaptively reduce chroma intra modes based on block texture. Experimental results show that we achieve a 47.3% encoding time reduction on average with a negligible quality loss of 0.062 dB for the Bjøntegaard delta peak signal-to-noise ratio when we compare our method to the HEVC test model 15.0. Index Terms-High efficiency video coding (HEVC), H.265, video compression, intra video coding, mode decision.

This paper presents an efficient method for encoding common projection formats in 360 • video coding, in which we exploit inactive regions. These regions are ignored in the reconstruction of the equirectangular format or the viewport in virtual reality applications. As the content of these pixels is irrelevant, we neglect the corresponding pixel values in ratedistortion optimization, residual transformation, as well as inloop filtering and achieve bitrate savings of up to 10%.

Virtual reality (VR) streaming is impaired by the large amount of data required to deliver 360-degree video resulting in low-quality end user experience when network bandwidth is limited, or latency is high. To address these challenges, proposed in this paper is a novel method for viewpoint prediction for long-term horizons in VR streaming. This method uses a long short-term memory (LSTM) encoder-decoder network to carry out a sequence-to-sequence prediction. To enhance the results obtained by this network, experiments are performed using viewpoint information from users on low-latency networks. By applying an effective tile-based quality assignment after viewpoint prediction, a 61% average bandwidth reduction, with respect to the transmission of the whole ERP frame, is achieved along with a high-quality viewport rendered to the end user.