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Table of Contents
HDR UHD Signalling
6.1.9 Signalling Transfer Function and Colour Space
The colour space and transfer function (SDR or HDR) are typically signalled in the VUI of an
H.265/HEVC or H.264/MPEG-4 AVC bitstream. As shown in the table below, there are two
methods of signalling the HLG transfer function.
In one method, the SDR transfer function indicator is signalled in the VUI and the HLG
transfer function indicator is transmitted using an alternative transfer characteristics SEI message
embedded in the bitstream. In this way, an “HLG aware” STB or decoder/display would
recognize that the bitstream refers to content coded with HLG (since it is indicated by the
preferred_transfer_characteristics syntax element of the SEI). If an “HLG aware” STB is
connected to a TV that does not support HLG, the STB would transmit the SDR indicator over
HDMI to the TV. If it is connected to a TV that supports HLG, the STB would copy over the
transfer function value in the SEI (to indicate HLG) and transmit this over HDMI to the TV.
In the other method, the HLG transfer function indicator is directly signalled in the VUI in the
same way PQ or SDR would be signalled.
AVP Modes
At the time of writing (Nov 2016) the AVP has just acquired a new menu for the signalling of HDR. This menu allows the operator to set the HDR signalling type. At this point in time, there is no support for HDR signalling in SDI (so the encoder can not detect SDR/HDR, or what type of HDR is being used).
