HD using HDMI vs SDI vs NDI vs ?

[matthewk]

We've been using NDI|HX cameras since 2016. I consider the latency "barely usable" but I haven't seen NDI (100MBPS) at the $1500 price point. Look out for false advertising as the "NDI" cameras are really only NDI|HX which is lower bitrate and higher latency

[Mikerowaved]

We've actually found a way to use the coax wired into our older building to transmit HDMI reliably. We found some "HDMI over coax" interface boxes
I can look up the reference to the units if you're interested.

How much delay are these introducing? Enough to cause A/V sync issues if we use the in-ceiling speakers?

I convert HDMI to SDI and run the signal over coax. The delay is minimal - maybe 1 frame at the most. Most of the delay I encounter is 2-3 frames from Wirecast. If you don't need titles or lyrics on the screen, you can split the HDMI from the camera and feed 1 signal to the Teradek box and the other to a rear projector.