I have some IP cameras, and also analog security cameras that are recorded by one of those Chinese 4 channel security recorders that have only analog video inputs.
I was wondering if I could somehow use a spare raspi to make the IP cameras send analog video out and have that 4 channel recorder record it. And if so, what the latency would be, and if it would sync at all.
Long time ago I wrote mcamip, later added support for those cheap Chinese IP cameras:
Compiled it on an old raspberry (the one with only 2 USB sockets), works there, booted the raspi in X, started mcamip in a terminal, and fed the analog video output to an input of the 4 channel recorder. Expected lots of latency? No, works perfectly. For the recorder to accept the signal I had to set sdtv_mode=2 in /boot/config.txt on the raspberry.
So that makes the raspi a digital to analog video converter, as opposed to the normal analog to digital... Those 4 channel recorders support a real haddisk for 24/7 recording.
You can make it auto-boot in X and mcamip too of course.
Ad then I connected to that 4 channel recorder and had a digital picture again... latency ..
FYI Proof of concept.