What is Blu-ray player?

In plain language

UHD Blu-ray carries 4K HDR video and lossless audio — TrueHD or DTS-HD MA, often with Atmos or DTS:X. The player decides what to output based on its own settings and what the chain advertises.

Why it matters in your setup

Disc content is where lossless audio actually lives, so a missing TrueHD or DTS-HD MA capability is more consequential here than anywhere else. If the chain does not advertise it, the player falls back to a compressed format silently.

Players also have HDR processing options that decide who does the work. Some can convert HDR10 and SDR to LLDV, and set Dolby Vision to player-led or display-led. Those settings change the picture more than most calibration controls do.

What the DR HDMI 8K does with it

The DR HDMI 8K's audio flags let you advertise TrueHD and DTS-HD MA explicitly rather than hoping they survive the chain, and the Dolby Vision data block controls are what a player-led LLDV setup needs on the other side. The manual includes specific notes on setting a player to player-led output and confirming it is really sending LLDV.