Hemantha Kodikara Arachchi

Toward an Impairment Metric for Stereoscopic Video: A Full-Reference Video Quality Metric to Assess Compressed Stereoscopic Video

The quality assessment of impaired stereoscopic video is a key element in designing and deploying advanced immersive media distribution platforms. A widely accepted quality metric to measure impairments of stereoscopic video is, however, still to be developed. As a step toward finding a solution to this problem, this paper proposes a full reference stereoscopic video quality metric to measure the perceptual quality of compressed stereoscopic video. A comprehensive set of subjective experiments is performed with 14 different stereoscopic video sequences, which are encoded using both the H.264 and high efficiency video coding compliant video codecs, to develop a subjective test results database of 116 test stimuli. The subjective results are analyzed using statistical techniques to uncover different patterns of subjective scoring for symmetrically and asymmetrically encoded stereoscopic video. The subjective result database is subsequently used for training and validating a simple but effective stereoscopic video quality metric considering heuristics of binocular vision. The proposed metric performs significantly better than state-of-the-art stereoscopic image and video quality metrics in predicting the subjective scores. The proposed metric and the subjective result database will be made publicly available, and it is expected that the proposed metric and the subjective assessments will have important uses in advanced 3D media delivery systems.

Sensitivity Analysis of the Human Visual System for Depth Cues in Stereoscopic 3-D Displays

Three-dimensional (3-D) displays provide a more realistic experience of entertainment by providing its viewers an added sensation of depth by artificially exploiting light rays to stimulate certain depth cues in the human visual system, especially binocular stereopsis. Due to its close relationship with human visual perception, mass market deployment of 3-D displays will be significantly dependant upon addressing the related perceptual factors such as visual comfort. In order to address the perceptual factors, it is very important to understand how humans experience depth on 3-D displays and how sensitive they are for different depth cues. In this paper, the sensitivity of humans for different depth cues is analyzed as applicable to 3-D viewing on stereoscopic displays. Mathematical models are derived to explain the just noticeable difference in depth (JNDD) for three different depth cues, namely binocular disparity, retinal blur, and relative size. Extensive subjective assessments are performed on a stereoscopic display with passive polarized glasses and on an auto-stereoscopic display to validate the mathematical models for JNDD. It is expected that the proposed models will have important use cases in 3-D display designing as well as 3-D content production.

A Platform for Context-Aware and Digital Rights Management-Enabled Content Adaptation

This article presents a scalable and modular platform for contextaware adaptation of multimedia content that is governed by digital rights management (DRM). This platform adopts several new approaches, such as (1) combining the use of ontologies and lowlevel context to drive the adaptation decision process, (2) verifying and enforcing usage rights within the adaptation operations, and (3) incorporating multifaceted adaptation tools to provide a wide range of on-the-fly and on-demand adaptation operations to suit various dynamic requirements.

Efficient coding unit size selection based on texture analysis for HEVC intra prediction

Determining the best partitioning structure for a given Coding Tree Unit (CTU) is one of the most time consuming operations within the HEVC encoder. The brute force search through quadtree hierarchy has a significant impact on the encoding time of high definition (HD) videos. This paper presents a fast coding unit size decision-taking algorithm for intra prediction in HEVC. The proposed algorithm utilizes a low complex texture analysis technique based on the local range property of a pixel in a given neighborhood. Simulation results show that the proposed algorithm achieves an average of 72.24% encoding time efficiency improvement with similar rate distortion performance compared to HEVC reference software HM12.0 for HD videos.

Assessing the Effects of Ambient Illumination Change in Usage Environment on 3D Video Perception for User Centric Media Access and Consumption

For enjoying 3D video to its full extent, access and consumption of 3D content should be user centric, which in turn ensures enhanced quality of user experience. The experience nevertheless is easily influenced by several factors, including content characteristics, users’ preferences, contexts prevailing in various usage environments, etc. Utilizing ambient illumination as an environmental context for the purposes of efficient provision of 3D video to users has particularly not been studied in literature in detail. This paper investigates the effects of ambient illumination on 3D video quality and depth perception for utilizing this information as one of the key context elements in future user centric 3D access and consumption environments. Subjective tests conducted under different illumination conditions demonstrate that the illumination of the viewing environment encircling the users has significant effects on the perceived 3D video quality as well as depth perception.

QoE aware resource allocation for video communications over LTE based mobile networks

As the limits of video compression and usable wireless radio resources are exhausted, providing increased protection to critical data is regarded as a way forward to increase the effective capacity for delivering video data. This paper explores the provisioning of selective protection in the physical layer to critical video data and evaluates its effectiveness when transmitted through a wireless multipath fading channel. In this paper, the transmission of HEVC encoded video through an LTE-A wireless channel is considered. HEVC encoded video data is ranked based on how often each area of the picture is referenced by subsequent frames within a GOP in the sequence. The critical video data is allotted to the most robust OFDM resource blocks (RBs), which are the radio resources in the time-frequency domain of the LTE-A physical layer, to provide superior protection. The RBs are ranked based on a prediction for their robustness against noise. Simulation results show that the proposed content aware resource allocation scheme helps to improve the objective video quality up to 37dB at lower channel SNR levels when compared against the reference system, which treats video data uniformly. Alternatively, with the proposed technique the transmitted signal power can be lowered by 30% without sacrificing video quality at the receiver.

Architectures and Technologies for Adapting Secured Content in Governed Multimedia Applications

This article analyzes existing initiatives and proposes new technologies for the governed adaptations of secured content in heterogeneous environments. These technologies are integrated into an architecture for the secure management of multimedia content.

Utilising Macroblock SKIP Mode Information to Accelerate Cropping of an H.264/AVC Encoded Video Sequence for User Centric Content Adaptation

Constraints on the storage, transmission and consumption deter seamless access to massive supply of multimedia contents readily available for consumers. Consequently, universal multimedia access (UMA) still remains a challenging objective. Context based digital item adaptation (DIA) is seen as a key technology to realise UMA. Scalability options in modern video coding standards provide inherent support for video adaptation. However, it is unlikely that all digital items (DIs) are coded with required scalability options. User centric adaptation adds even more strain on scalability. One such application is to deliver a user defined region of interest (ROI) from a high resolution video to a low resolution terminal. Transcoding is still the solution for such adaptation scenarios. This paper discusses a framework to accomplish such adaptation in H.264 coded video and demonstrates the effectiveness of utilising SKIP mode macroblocks to reduce the transcoding complexity.

Adaptive residual mapping for an efficient extension layer coding in two-layer HDR video coding

In the absence of a commercial High Dynamic Range (HDR) distribution pipeline, two-layer backward-compatible HDR video coding is a viable solution for the imminent transition from Low Dynamic Range (LDR) to HDR content transmission. However, the performance of a two-layer coding solution is governed by the extension layer coding performance. In this paper, we propose an improved two-layer backward-compatible HDR video coding solution based on an adaptive residual mapping for the extension layer, keeping in view the performance of High Efficiency Video Coding (HEVC) being used to code this information. The proposed solution outperforms the reference method achieving averaged PU-PSNR improvements of up to 5.05 dB. The proposed method also shows potential of achieving the same HDR quality as the single layer coding solution with a minimum bitrate overhead and acceptable LDR quality in the base layer.

Advanced delivery of sensitive multimedia content for better serving user expectations in Virtual Collaboration applications

A major challenge when accessing protected multimedia content in heterogeneous usage environments is the ability to provide acceptable levels of quality of experience to all involving users. Additionally, different levels of protection should be possible to be addressed when manipulating the content towards the quality of experience maximization. This paper describes the use of a context-aware and Digital Rights Management (DRM)-enabled content adaptation platform towards meeting these challenges. The platform was conceived to deliver advanced content adaptation within different application scenarios, among which Virtual Collaboration (VC) was central. Descriptions of use cases implemented by the platform in heterogeneous VC environments are provided. Conducted experiments have highlighted the benefits to users when compared to an operation without the platform. Results of different adaptations suitable to sensed context conditions are also provided and analyzed. A brief description of the platform functionality is included together with pointers to additional information.