There is so much more to this than just the type of cable, which probably makes little difference in the grand scheme.
What really does matter are things like video format, frame rate, video scan type, the type of cameras, projector and the entire video chain when it comes to what you total latency will be. Its not a single device, but all of them added together. If you just slap together a bunch of parts hoping that latency will be low, it will most likely not be.
Getting low latency takes work, testing, possibly changing out gear and making some compromises. Beyond that, if this is a very large venue, you aren't going to be able to get perfect a/v sync everywhere, because light and sound travel at such different speeds from each other. At 30fps, sound travels about 11 meters (37 feet) per video frame. For example, say you are in a large venue with perfect a/v sync output, and you are 150 feet from the screen/speakers you are dealing with a 4 frame a/v sync that all caused by physics. Where as people directly in front of the screen will have no a/v sync issues.
Here are a few things that I could recommend.
1. Work progressive, no interlace video formats!
2. Work in the highest frame rate possible, if you can't do 1080p60, then do 720p60.
3. Don't convert between video formats (use the same frame rate and resolution everywhere).
4. Don't externally change between cables types (like digital to analog, HDMI to SDI, etc).
5. Some cameras have latency from lens to output, turn off any processing in the camera (like image stabilization).
6. The output device is usually the highest latency device in most setups. Find out what the native resolution of the output device (projector) and work in the video format. If your projector doesn't work in a native video resolution (720 or 1080p) think about replacing it with one that does.
7. Turn off all image processing in your output device (keystone adjustment is a big no!)
8. Use genlock
9. Disable the input frame syncs (you can do this on a TriCaster, can it be done on a vMix input card?)
All of these ideas are just recommendations, and you would need to test your specific setup to see which ones matter. In some cases, you might find a different answer than what I'm recommending.
Most people would say that 3 frames (100ms) or less of latency can't be noticed by the average person and 6 frames (200ms) or less would probably be acceptable to most people. By average people, I mean your typical person off the street, not a video professional that will agonize over every frame they can measure.
Can NDI be used? Possibly. It's typically a frame or less to convert from a baseband video sources into NDI. But again, this is all additive. For some configurations that extra frame will not be a problem, but in some video chains, you will be working to get back each and every frame of latency you possibly can. On the flip side, going NDI to a computer outputting at the native resolution of your projector might improve things versus using an input that isn't native resolution.
Finally, I'm not a vMix expert, there might be other things I'm not aware of with this system. The above is what I would tell a TriCaster user.
Kane Peterson
NewTek
