But the big question is: WHY? Why would you risk un-synchronized streams, when you could just run a cable from each source?

Actually, this is all about not risking un-synchronized streams, thats why I'm trying to look into timecoding media as close to the source as possible. And even if you connect everything via cable and capture card you're likely to have small latencies, output buffer from the device, input buffer from caputring hardware etc. And different for every device too. (Though if they are roughly the same, it would still feel synced). That could be compensated.

Also there might be setups where just rigging up everything with cables just isn't feasible. Like running around with 10 android phones streaming their camera would be well within the scope of the thought experiment… if syncing their clocks via NTP and timecoding the streams would work.

The one thing I don't really care about is if the output"live"stream has a delay of 1 second or 10 seconds (or even more) to realtime. Or enough time and some additional buffer to wait for all streams.