Windows capture latency
After a discussion with @keftaparty about latency differences between thunderbolt and pcie blackmagic capture. I compared a deckilink duo 2 and a mini recorder. The setup was a timecode movie playing from my laptop while mirroring to a HDMI to SDI convertor, one SDI output connected to the mini recorder and one to the duo. The mini recorder shows 3 frames latency and the pcie card 2.5 (all this is at 25fps, so 120ms or 100ms latency.
The mini recorder does not capture 50fps so I could not do further tests but the duo does and maintained 100ms latency. There may be latency added by the HDMI to SDI convertor and of course by the screen, but the test seems consistent with my previous results and other peoples experience.
Here is a video of the output, more detailed data could be collected with an SDI signal analyser.