HDR and Dolby Vision

HDR

High Dynamic Range

HDR is only partly about the pixels. Most of what a display does with an HDR signal comes from the metadata, and metadata is exactly what the Diva can rewrite.

HDR stands for High Dynamic Range. Standard dynamic range video was defined around the behaviour of a cathode ray tube and tops out near 100 nits. HDR uses a different transfer curve, so the same ten or twelve bits per channel describe a range from near black up to a thousand nits and beyond. The gain shows in specular highlights and shadow detail rather than in overall brightness.

Two curves are in common use. PQ, standardised as SMPTE ST 2084, is absolute: a code value means a fixed number of nits, which is why PQ content carries metadata saying how bright the master was. HLG, from ITU-R BT.2100, is relative and needs no metadata, which suits broadcast. HDR10 is PQ with static metadata, and Dolby Vision adds metadata that changes scene by scene.

The metadata is where most of the behaviour lives. It travels in an infoframe alongside the picture, and it is what puts a display into its HDR mode and tells it what to tone map towards.

What the HDfury Diva does with HDR

The HDR/DV section captures what arrives and lets you change it. CAPTURED HDR METADATA shows the incoming infoframe in hex and in readable form. The custom HDR metadata generator below it builds your own from EOTF, Primaries, White Point, Max Luminance, MaxCLL, Min Luminance and MaxFALL, the last four valid from 1 to 65535. Click Create IF, then Send HDR.

Checkboxes decide when your version is used. All are unchecked by default and all persist over hot plugs and power cycles. They run from unconditional injection, set hdrcustom on, through conditional versions for HDR10 and HLG input, to the cancelling options: set hdrdisablehdr10only on stops incoming HDR10 metadata while HLG still passes, and set hdrdisable on stops all of it.

Turning HDR into SDR

TX1 is an HDR to SDR 1080p output, and the tone-mapping profile that governs the conversion sits in the TOOLS section under PROFILE. Most people get the best result from Profile 2, although some displays render slightly better colours on a neighbouring one, so try them on real content. The command is set hdrprofile 2, with 0 for OFF, and it applies only when the input is HDR10.

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