HDMI 2.0’s data bandwidth is 18Gbps. Display Port 1.4’s is 25.92 Gbps. Thunderbolt on the framework is 40Gbps (32 Gbps practical). Doesn’t this, therefore, mean that the laptop could capture these display technologies and save/stream them accordingly, without any intermediate chip? (HDMI might require a license though)
I’m a little confused, do you mean can the laptop process/capture an external video source? Or capture video from say a video game you are playing on the laptop? The answer is yes either way but I am confused as to why you would need an intermediate chip
Either Quick Sync or the CPU proper would handle the processing
PCIe 3.0 x4 is 32 Gbps * 128b/130b = 31.5 Gbps but there’s also a lot of PCIe overhead so maybe the limit is more like 3500 MB/s (28 Gbps).
Thunderbolt can do ≈23 Gbps of PCIe data; not 32 Gbps. The rest of the 40 Gbps can only be used by DisplayPort (up to 34.56 Gbps or 38.9 Gbps if you’re using an Apple Pro Display XDR with macOS connected to a GPU that doesn’t support DSC).
HDMI 2.0 is 14.4 Gbps (considering 8b/10b encoding like you did for DisplayPort).
For what you want, you need a HDMI capture card in a Thunderbolt PCIe expansion chassis connected via Thunderbolt. A USB solution (5 or 10 Gbps) will be much less expensive but would use compression.
You need at least a Thunderbolt controller chip (included in the Thunderbolt PCIe expansion chassis) to communicate via Thunderbolt. I suppose that chip can have a DisplayPort input but I don’t know if there’s a method to pipe that DisplayPort data to the host - maybe by poking some Thunderbolt controller registers?
Apple had a Thunderbolt Target Display Mode that allowed using an old iMac (2011-2014) as a display (1440p) by using a Thunderbolt connection but I don’t know how that was done. I’ve not looked at the drivers involved - there’s a source driver on the first Mac and sink driver on the iMac. This wouldn’t work from a PC unless you ported the source driver. I suppose you would need access to the same DMA stuff that Thunderbolt IP uses if the driver is not using DisplayPort tunnelling. Thunderbolt IP has drivers for macOS, Windows, and Linux. I think Apple is the only one to use the Thunderbolt DMA communication for anything else (Target Display Mode and Target Disk Mode).
Before Thunderbolt iMacs, older iMacs (2009-2010) used DisplayPort input for Target Display Mode. I suppose that just used some DisplayPort mux switch to pipe the DisplayPort input directly to the display. That way even a PC could use the iMac for the display.
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Looks like this might need a TinyFPGA to facilitate the data translation.