Bit Rate Requirements for High Dynamic Range Video

High dynamic range (HDR) video can offer consumers a much improved viewing experience compared to current broadcast video. The dynamic range of current television images, referred to as standard dynamic range (SDR), is governed by cathode ray tube physics first documented about eighty years ago. The standards include the Electro-Optical Transfer Function (EOTF) and the Opto-Electrical Transfer Function (OETF), as defined in International Telecommunications Union Radiocommunication (ITU-R) Recommendations BT.1886 and ITU-R BT.709, respectively. Alternative transfer functions have been defined to support the transmission and rendering of HDR video signals. These transfer functions aim to provide perceptually uniform mapping of video signals to the higher luminance range of HDR displays while maintaining video signal bit depths used across current broadcast infrastructures. In consequence, these new transfer functions exhibit much higher non-linearity compared to the transfer functions used in today's SDR systems. This could lead to several implications, such as an increase in bit rates required to transmit HDR services; changes to the existing broadcast infrastructure, including graphics equipment and vision mixers; and the compatibility of HDR services with existing SDR displays. This paper studies the impact of such transfer functions on the efficiency of the video compression used for delivery to the final user. Results, in terms of compression efficiency and subjective picture quality, using single-layer High Efficiency Video Coding (HEVC, also known as H.265 and MPEG-H Part 2) video compression algorithms are presented. This seeks to answer the question of what bit rates will be required to provide HDR services using existing video compression technology.