Displays capable of showing a greater range of luminance values can render content containing high dynamic range information in a way such that the viewers have a more immersive experience. This paper introduces the design aspects of a high dynamic range (HDR) system, and examines the performance of the HDR processing chain in terms of compression efficiency. Specifically it examines the relation between recently introduced Society of Motion Picture and Television Engineers (SMPTE) ST 2084 transfer function and the High Efficiency Video Coding (HEVC) standard. SMPTE ST 2084 is designed to cover the full range of an HDR signal from 0 to 10,000 nits, however in many situations the valid signal range of actual video might be smaller than SMPTE ST 2084 supported range. The above restricted signal range results in restricted range of code values for input video data and adversely impacts compression efficiency. In this paper, we propose a code value remapping method that extends the restricted range code values into the full range code values so that the existing standards such as HEVC may better compress the video content. The paper also identifies related non-normative encoder-only changes that are required for remapping method for a fair comparison with anchor. Results are presented comparing the efficiency of the current approach versus the proposed remapping method for HM-16.2.
The high efficiency video coding (HEVC) standard being developed by ITU-T VCEG and ISO/IEC MPEG
achieves a compression goal of reducing the bitrate by half for the same visual quality when compared with
earlier video compression standards such as H.264/AVC. It achieves this goal with the use of several new tools
such as quad-tree based partitioning of data, larger block sizes, improved intra prediction, the use of sophisticated
prediction of motion information, inclusion of an in-loop sample adaptive offset process etc. This paper describes
an approach where the HEVC framework is extended to achieve spatial scalability using a multi-loop approach.
The enhancement layer inter-predictive coding efficiency is improved by including within the decoded picture
buffer multiple up-sampled versions of the decoded base layer picture. This approach has the advantage of
achieving significant coding gains with a simple extension of the base layer tools such as inter-prediction, motion
information signaling etc. Coding efficiency of the enhancement layer is further improved using adaptive loop
filter and internal bit-depth increment. The performance of the proposed scalable video coding approach is
compared to simulcast transmission of video data using high efficiency model version 6.1 (HM-6.1). The bitrate
savings are measured using Bjontegaard Delta (BD) rate for a spatial scalability factor of 2 and 1.5 respectively
when compared with simulcast anchors. It is observed that the proposed approach provides an average luma BD
rate gains of 33.7% and 50.5% respectively.