The majority of internet traffic is video content. This drives the demand for video compression in order to deliver high quality video at low target bitrates. This paper investigates the impact of adjusting the rate distortion equation on compression performance. An constant of proportionality, k, is used to modify the Lagrange multiplier used in H.265 (HEVC). Direct optimisation methods are deployed to maximise BD-Rate improvement for a particular clip. This leads to up to 21% BD-Rate improvement for an individual clip. Furthermore we use a more realistic corpus of material provided by YouTube. The results show that direct optimisation using BD-rate as the objective function can lead to further gains in bitrate savings that are not available with previous approaches.
In this paper, we present a statistical characterization of tile decoding time of 360° videos encoded via HEVC that considers different tiling patterns and quality levels (i.e., bitrates). In particular, we present results for probability density function estimation of tile decoding time based on a series of experiments carried out over a set of 360° videos with different spatial and temporal characteristics. Additionally, we investigate the extent to which tile decoding time is correlated with tile bitrate (at chunk level), so that DASH-based video streaming can make possible use of such an information to infer tile decoding time. The results of this work may help in the design of queueing or control theory-based adaptive bitrate (ABR) algorithms for 360° video streaming.
The H.265/HEVC (High Efficiency Video Coding) codec and its 3D extensions have crucial rate-distortion mechanisms that help determine coding efficiency. We have introduced in this work a new system of Lagrangian parameterization in RDO cost functions, based on semantic cues in an image, starting with the current HEVC formulation of the Lagrangian hyper-parameter heuristics. Two semantic scenery flag algorithms are presented and tested within the Lagrangian formulation as weighted factors. The investigation of whether the semantic gap between the coder and the image content is holding back the block-coding mechanisms as a whole from achieving greater efficiency has yielded a positive answer.
High Efficiency Video Coding (HEVC) is the latest video coding standard. The residual quadtree (RQT) coding structure which provides variable block size for transform coding, is adopted in HEVC to achieve high coding efficiency. However, compared with previous standards, encoding complexity is increased significantly in HEVC due to the advanced encoding structure. A fast transform unit (TU) mode decision algorithm using residual difference is proposed in this paper to reduce the computational complexity. The proposed algorithm utilized the residual difference to determine the criterion of early TU termination and early TU skip. The threshold was trained from the beginning samples of each sequence. Experimental results showed that the proposed algorithm saves up to 75.64% and on average 64% TU encoding time compared with HM 15.0 in low delay P configuration and the loss of average BD-BR is less than 0.5%.
The latest High Efficiency Video Coding (HEVC) standard achieves about 50% bit rate saving while maintaining the same subjective quality compared to H.264/AVC High Profile. However, the better coding efficiency is obtained at the cost of significantly increased encoder complexity. In this paper, a fast mode decision algorithm is proposed to relieve the computational burden. The proposed algorithm consists of two steps. Firstly, depth information of CU block is used to reduce the mode candidates, with the assumption that the exhaustive search for a large CU is unnecessary. Secondly, a directional ratio is applied to estimate the rough orientation of each CU, thus some unlikely selected directional modes can be further eliminated. On average, the proposed algorithm can achieve 34.1% encoder time saving while cause an negligible coding performance loss under the All-Intra configuration compared with HM 16.0.
This paper presents an efficient algorithm for motion estimation to reduce High Efficiency Video Coding (HEVC) standard encoding complexity. Phase correlation is initially utilized as a preprocessing step to indicate an approximation of the shift between coding units in the current frame and the reference frame. This is followed by a 9-point diamond search centered on the shift found in the initial step, in order to refine the best matching block. The proposed method has the potential to yield substantial improvements in terms of execution time and resulting video quality in comparison to the traditional search methods.
This paper investigates the compression of infrared images with three codecs: JPEG2000, JPEG-XT and HEVC. Results are evaluated in terms of SNR, Mean Relative Squared Error (MRSE) and the HDR-VDP2 quality metric. JPEG2000 and HEVC perform fairy similar and better than JPEG-XT. JPEG2000 performs best for bits-per-pixel rates below 1.4 bpp, while HEVC obtains best performance in the range 1.4 to 6.5 bpp. The compression performance is also evaluated based on maximum errors. These results also show that HEVC can achieve a precision of 1°C with an average of 1.3 bpp.
Google started the WebM Project in 2010 to develop open source, royalty--free video codecs designed specifically for media on the Web. Subsequently, Google jointly founded a consortium of major tech companies called the Alliance for Open Media (AOM) to develop a new codec AV1, aiming at a next edition codec that achieves at least a generational improvement in coding efficiency over VP9. This paper proposes a new coding tool as one of the many efforts devoted to AOM/AV1. In particular, we propose a second ALTREF_FRAME in the AV1 syntax, which brings the total reference frames to seven on top of the work presented in [11]. ALTREF_FRAME is a constructed, no-show reference obtained through temporal filtering of a look-ahead frame. The use of twoALTREF_FRAMEs adds further flexibility to the multi-layer, multi-reference symmetric framework, and provides a great potential for the overall Rate- Distortion (RD) performance enhancement. The experimental results have been collected over several video test sets of various resolutions and characteristics both texture- and motion-wise, which demonstrate that the proposed approach achieves a consistent coding gain, compared against the AV1 baseline as well as against the results in [11]. For instance, using overall-PSNR as the distortion metric, an average bitrate saving of 5.880% in BDRate is obtained for the CIF-level resolution set, and 4.595% on average for the VGA-level resolution set.