A “Display Independent” High Dynamic Range Television System

Abstract

High Dynamic Range (HDR) television has captured the imagination of the broadcast and movie industries. This paper presents an overview of the BBC’s “Hybrid Log-Gamma” solution, designed to meet the requirements of high dynamic range television. The signal is “display independent” and requires no complex “mastering metadata”. In addition to providing high quality high dynamic range (HDR) pictures it also delivers a high quality “compatible” image to legacy standard dynamic range (SDR) screens and can be mixed, re-sized and compressed using standard tools and equipment. The technical requirements for a high quality HDR television system are presented. Quantisation effects (or “banding”) are analysed theoretically and confirmed experimentally. It is shown that quantisation effects are comparable or below competing HDR solutions. The psychovisual effects of presenting image on emissive displays in dim environments. “System gamma”, is shown experimentally and the analysis informs the design of this HDR system. This document was originally presented at the IBC 2015 Conference 10-14 September 2015, and the slides used are included as an appendix.

Note (February 2017): The pre-standard HLG (Hybrid Log-Gamma) transfer characteristic described in this paper has been superseded by ITU-R BT.2100.

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