Diva features

ALLM

Auto Low Latency Mode

ALLM is why a console can put a television into game mode without anyone reaching for a remote. The Diva has no ALLM switch of its own, but it sits on the path the flag travels and can be told to keep it intact.

ALLM stands for Auto Low Latency Mode. The source sets a bit in the HDMI Forum vendor specific infoframe, the small packet it sends alongside the picture, and the display responds by selecting its own low latency preset: the picture processing that adds frames of delay is bypassed until the bit clears again. A sink says it understands the request by advertising it in the HDMI Forum vendor specific data block inside its EDID. The mechanism was defined with the HDMI 2.1 specification, but the signalling is carried in an infoframe and an EDID block, so it does not itself require more bandwidth.

It is worth being clear about what ALLM is not. It changes nothing in the video: no resolution, frame rate, colour or HDR difference. It does not guarantee the lowest latency a panel is capable of, only that the panel selects whatever it calls its game mode. And it is a separate matter from variable refresh rate, which the Diva does not carry: the two are often named in the same breath but they are unrelated features.

ALLM on the HDfury Diva

There is no ALLM control in the web server, because the flag is not something the Diva generates. What matters is whether the declaration in the EDID reaches your source, and whether the infoframe from your source reaches the display. The HDR/DV section reports HFV INFOFRAME, the HDMI Forum vendor specific infoframe, whenever the source sends one, which is where you confirm the source is actually asking for anything.

On the EDID side, COPY TX0 SINK hands the source the display's own EDID, which is the surest way of keeping an ALLM declaration intact. In CUSTOM mode, bank 4 is CUSTOM 4 [Q9FN ALLM VRR HDR10+] with full sound and 3D, an EDID captured from a television that declares ALLM, and it can be assigned to one input with set edidtableinp0 for input 1 and the matching inp1, inp2 and inp3 commands for the others. Automix is the weak choice here: its fourteen flags cover audio, HDR, colour and Dolby Vision, and none of them forces ALLM, so the declaration survives only if the mixed sinks provide it.

Proving that it worked

The Diva can measure the difference itself. The TOOLS section holds ACTIVATE LAG TEST, TARGET, which places the measurement window at left top, centre or right bottom, and START TEST, which reports the result in the top left corner of the screen to one decimal place in milliseconds. The test runs on the TX1 output, so for a 4K HDR measurement you loop TX1 back into a Diva input and route that input to TX0, with scaling left at its defaults. Measure the display with its game mode off and again with it on, and you have a number rather than an impression. The unit itself adds latency in the order of a few pixel clocks.

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