High Dynamic Range versus Standard Dynamic Range compression efficiency

Abstract

High Dynamic Range (HDR) image and video technology aims at conveying the full range of perceptible shadow and highlight details with sufficient precision. HDR is regarded by many experts as the next evolution in digital media. However, industrial broadcasters have concerns regarding the bandwidth overhead that this new technology entails. While many consider that broadcasting HDR content would increase bandwidth requirements by around 20%, this number is based on studies where, in addition to the SDR main stream, HDR-related side information is conveyed. A recent subjective evaluation reported that encoding HDR video content in a single layer might require less bandwidth than its associated SDR version. Similar results were discussed in the MPEG ad-hoc group on High Dynamic Range and Wide Color Gamut. In this article, we explain how having more information can result in lower bandwidth requirements. To this end, we describe several limitations of the human vision system that, when exploited, optimize the HDR distribution pipeline for a human observer. Our theoretical assumption about the higher efficiency of HDR is backed up by a statistical analysis of pixel distribution in real images. The Spatial Index objective metric also reconfirms our assumption.