Ajay Luthra

Video compression for multicast environments using spatial scalability and simulcast coding

A common problem with many video transmission applications is the wide range of available bandwidths between the server and different clients. These environments require efficient multicast video service, the capability to transmit and receive the same video sequence at different resolutions. Two approaches to achieve multicast service are scalable coding (dependent bitstream coding) and simulcast coding (independent bitstream coding). One would expect scalable coding to have higher coding efficiency because a scalable coded bitstream can exploit similar information in another bitstream. This reasoning would suggest that multicast implementations should only use scalable coding for maximum coding efficiency. However, this article shows results where simulcast coding has been found to outperform spatial scalability (one type of scalable coding). In this article, methods are described to select between simulcast coding and spatial scalability for multicast video transmission. These techniques can be used to determine the proper multicast coding approach for providing service to clients with different communication links. The methodology described can also be used to construct decision regions to guide more general scenarios or adaptively switch between the two coding approaches. A number of important results were obtained that may be directly applicable to commercial multicast systems.

MPEG-2 multiview profile and its application in 3D TV

Recent developments in the technology of digital video compression, transmission and displays have made the multiple viewpoint digital video viable for many applications, e.g. stereoscopic view for 3D TV and arbitrary angle scene compositing for virtual camera, etc. To facilitate these applications the Motion Pictures Experts Group (MPEG) of the International Standards Organization (ISO), that successfully created the MPEG-1 & 2 standards, has been working on amending the MPEG-2 standard to create a new MPEG-2 profile, called the Multi-View Profile (MVP). MVP features a two-layer -- base layer and enhancement layer -- video coding scheme. The base layer video is coded as MPEG-2 main profile (MP) bitstream. The enhancement layer video is coded with temporal scalability tools and exploits the correlation between the two viewing angles to improve the compression efficiency. This type of two layer approach guarantees backward and forward compatibility with main profile receivers and encoders; i.e. an MVP decoder will be able to decode any main profile bit stream at the same level and a main profile receiver will be able to decode the base layer of an MVP stream to generate and display mono view scenes of the same program. In stereoscopic video applications the base layer is assigned to the left eye view and the enhancement layer to the right eye view. This paper provides an overview of the MPEG-2 MVP and focuses in detail on the stereoscopic video compression algorithms.

On metrics for objective and subjective evaluation of high dynamic range video

In high dynamic range (HDR) video, it is possible to represent a wider range of intensities and contrasts compared to the current standard dynamic range (SDR) video. HDR video can simultaneously preserve details in very bright and very dark areas of a scene whereas these details become lost or washed out in SDR video. Because the perceived quality due to this increased fidelity may not fit the same model of perceived quality in the SDR video, it is not clear whether the objective metrics that have been widely used and studied for SDR visual experience are reasonably accurate for HDR cases, in terms of correlation with subjective measurement for HDR video quality. This paper investigates several objective metrics and their correlation to subjective quality for a variety of HDR video content. Results are given for the case of HDR content compressed at different bit rates. In addition to rating the relevance of each objective metric in terms of its correlation to the subjective measurements, comparisons are also presented to show how closely different objective metrics can predict the results obtained by subjective quality assessment in terms of coding efficiency provided by different coding processes.