HDR and Dolby Vision

Dolby Vision

Dolby's dynamic HDR system

Dolby Vision is the HDR format that argues most with whatever sits in the middle of a chain. The Diva reads the metadata arriving from the source, reads the Dolby Vision string offered by the display, and can present either to the other.

Dolby Vision is a High Dynamic Range system introduced in 2014. Where HDR10 sends one set of static values describing the whole programme, Dolby Vision carries metadata that changes through the film, so the mapping from the mastering display to yours can be recalculated scene by scene or frame by frame. It works in a container of up to 12 bits and its metadata rides inside the video stream rather than in a separate infoframe.

A sink declares Dolby Vision support with a Dolby Vision data block in its EDID, usually called the mandatory string, rather than through the ordinary HDR static metadata block. That string is the whole negotiation: if a source cannot see it, it never offers Dolby Vision and falls back to HDR10 or SDR. This is why inserting an AVR, a splitter or a matrix that does not carry the block forward is the classic way to lose Dolby Vision without any error appearing.

There are two broad delivery styles. In the display-led form the television performs the mapping itself. In the source-led form the player does the work and sends a signal the display treats more conventionally, which is what LLDV is.

Dolby Vision on the HDfury Diva

The HDR/DV section shows both halves of the exchange. CAPTURED INPUT DOLBY VISION METADATA reports the Dolby ID and hex data coming from the source. Separately, the Diva automatically sniffs, displays and saves any Dolby Vision mandatory string from a sink connected at TX0, and deciphers the data block into readable form.

Saving it is what makes the feature more than informative. Once a display's string is stored, it can be used in Automix to keep the stream from the source compatible with that sink, and you can then insert an AVR or other equipment into the chain and still have the correct signal reach the display. Three Automix flags act on it: DV Force Metadata, DV Remove and DV Limit 300MHz, reachable over control as set edid dv, set edid dvremove and set edid dvlimit, each on or off. Several custom EDID banks also ship with strings taken from real displays, among them CUSTOM 2 with LG DV, CUSTOM 5 with SONY A1 LLDV V2 and CUSTOM 7 with VIZIO M50E1 DV V0.

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 it can sniff the string from the television's EDID.
3. Disconnect that cable and insert the AVR or other equipment you wanted in the chain.
4. Check the EDID rows in the INFO section to confirm the sources are still being told what you intended.

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