HDR and Dolby Vision

LLDV

Low Latency Dolby Vision

In LLDV the clever work happens in the source rather than the television. That is why it is fast, and also why it depends completely on what the display told the source about itself.

LLDV expands to Low Latency Dolby Vision. In standard Dolby Vision the source passes the metadata through and the display does the tone mapping, applying its own knowledge of its peak brightness and its panel. In LLDV the source reads the display Dolby Vision capability out of the EDID, does the mapping itself, and hands over a picture already fitted to that display. The television then switches into a fixed, minimal processing mode and shows what it is given.

The gain is latency, which matters for games and for user interfaces that have to respond to a remote. The side effect is more interesting: because the result travels as an ordinary HDMI signal with the metadata tunnelled inside it, Dolby Vision can reach a display through equipment that has no idea what Dolby Vision is. Modes 0 and 1 use an 8-bit RGB container, so a device reporting RGB 8b while such a stream plays is reporting the truth and nothing has been lost.

LLDV on the HDfury Diva

All four inputs accept 4K HDR, HLG, Dolby Vision, LLDV and HDR10+ up to 18Gbps, and the incoming signal line names the flavour in use directly: 4K50 4:2:2 BT2020 12b LLDV 594MHz 2.2 on the OLED tells you resolution and frame rate, subsampling, colorimetry, bit depth, the Dolby Vision variant, the pixel clock and the HDCP revision in one line.

The part worth knowing about is the Dolby Vision EDID datablock. The Diva automatically sniffs, displays and saves any Dolby Vision mandatory string from a sink connected at TX0, and deciphers it into readable form in the HDR and DV section. Once that string is stored it can be used in Automix, so you can insert an amplifier or other equipment into the chain afterwards and still have the correct Dolby Vision signal reach the display. Three Automix flags act on it: DV Force Metadata, set edid dv on, DV Remove, set edid dvremove on, and DV Limit 300MHz, set edid dvlimit on.

If you would rather present a known good string than a sniffed one, several of the custom EDID banks already hold Dolby Vision strings taken from real displays, among them CUSTOM 5 [SONY A1 LLDV V2] and CUSTOM 6 [LG35C7 DV V1].

The connection order that makes it work

1. Connect the Diva TX0 output straight to the Dolby Vision television, with nothing in between.
2. Let the Diva boot, so that it reads and stores the Dolby Vision string from that television.
3. Disconnect, and insert the amplifier or other equipment in the middle of the run.
4. Check the HDR and DV section to confirm the stored string is still the one you want presented to the sources.

All glossary terms