HDR and Dolby Vision

Dolby Vision data block

The EDID block that declares DV support

Dolby Vision only starts if the source finds the right block in the EDID it reads. The Diva saves that block from your television and can then present it on your behalf.

Dolby Vision is declared in an EDID by a vendor specific data block inside the CTA extension. It carries Dolby's registered identifier and a short set of fields: the version of the block, the maximum pixel clock the display will accept for Dolby Vision, and which form of the format it wants. A source that does not find this block will not offer Dolby Vision at all, whatever the disc or the app contains.

Several versions exist, commonly written V0, V1 and V2. They differ in what they describe rather than in picture quality. The block is separate from the HDR static metadata block that declares HDR10 and HLG, so a display can advertise one and not the other, and a chain can pass HDR10 perfectly while Dolby Vision never appears.

How the HDfury Diva handles the Dolby Vision data block

The Diva automatically sniffs, displays and saves any Dolby Vision mandatory string from a sink connected at TX0, and deciphers the datablock into human readable form in the HDR/DV section. Storage is what makes the feature useful rather than merely informative: once your television's string is saved, you can insert an AVR or other equipment into the chain and the right Dolby Vision signal still reaches the sink.

Three AUTOMIX flags act on it. DV Force Metadata makes the mixed EDID present Dolby Vision support, DV Remove makes it present none, and DV Limit 300MHz allows Dolby Vision only at 300MHz. Over RS232 or IP those are set edid dv on, set edid dvremove on and set edid dvlimit on.

Several of the ten custom EDID banks already hold Dolby Vision strings taken from real displays, among them CUSTOM 2 [FULL + LG DV], CUSTOM 5 [SONY A1 LLDV V2], CUSTOM 6 [LG35C7 DV V1] and CUSTOM 7 [VIZIO M50E1 DV V0]. In CUSTOM mode you assign one of those to a single input, so a disc player can be told a different story from a games console.

Capturing the string in the first place

1. Connect the TX0 output straight to the Dolby Vision television, with nothing in between.
2. Power the Diva and let it boot, so that it reads the display EDID and stores the Dolby Vision string.
3. Disconnect, then insert the AVR or other equipment back into the chain.
4. Check the captured datablock in the HDR/DV section, then set the flags you need in AUTOMIX.

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