What is Dolby Vision data block?

In plain language

Inside an EDID extension block sits a vendor-specific block describing Dolby Vision support: which interface version, which primaries, the luminance range, whether particular colour formats are supported.

Why it matters in your setup

This block is fragile in a way the rest of the EDID is not. Devices that rebuild EDID as they pass it through often drop vendor-specific blocks they do not understand, so the display's DV capability disappears somewhere in the middle. The player falls back to HDR10 silently, and everything looks fine except that the Dolby Vision logo never comes on.

Because the block also carries the primaries and the luminance values, its contents affect how the picture looks, not just whether DV engages.

What the DR HDMI 8K does with it

The DR HDMI 8K reads the DV data block from the connected display automatically, stores it, and shows it deciphered into human-readable form. The stored block can be inserted into an AutoMix EDID so it survives the rest of the chain, and you can build one by hand: interface, primaries, YUV422 12-bit, global dimming, backlight control, minimum luminance, and fully custom primary coordinates and luminance values.