What Bit Rate and Chroma Subsampling is actually going down my cables?

Beginners
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1

What bit rate and chroma subsampling is actually going down my cables?

My setup is:
NVIDIA RTX a5000 Quadro Sync II
TouchDesigner is sending a 8-bit fixed 3840x3840 30fps signal to the second display, which is a MOSAIC of two 4k DisplayPort 1.4 cables at the same setup, 3840 square, 30Hz.
It’s not a monitor at the other end of the cables; rather it’s a two-projector planetarium setup I can’t control: there’s a chain of DP->HDMI and HDMI->SDI splitters & converters bringing the signal to two PCs running the projectors.

If I don’t have much insight into the hardware except what’s on the computer running TouchDesigner:

  • How might I know the bit rate that I am outputting to the DisplayPort cables?
  • Is it always what TouchDesigner says it’s sending, in the right-click menu?
  • How might I know whether chroma subsampling is being applied?

My team is asking about adding an EDID Emulator to the chain of cables (to solve some tearing issues. I have studied the Perfect Playback blog post.)

Thank you!

2

We don’t interact or have any control over what goes over the wires. That is entirely controlled by the OS/driver, which you usually setup in the Nvidia Control Panel.
We simply send the OS a buffer that is usually 8-bit RGB (or 10-bit RGB if you are using 10-bit mode in TD). Then the driver will convert that to whatever format the wire requires.
The content of the TOPs don’t matter, those will be converted to 8 or 10 bit RGB, depending on what the Window COMP is running at.

3

Thank you.

If you can share with a beginner, where might I start with learning how the OS and GPU Driver behave, in terms of both (1) the baseline knowledge about how applications typically send graphics to monitors, and (2) where I can learn how Windows and NVIDIA do so? I am hitting a limit in my vocabulary and baseline understanding of these things that unguided Internet searching can’t get me past.

Thanks again!

4

Hard question to answer. Probably you’d want to learn about swapchains in Vulkan and DirectX. If you know those APIs, then you know they don’t offer a way to control what goes on the wire. You can go to the Nvidia Control Panel to see the settings are controlled in there.