Newbie: What is CasparCG and is it a good basis for my needs?

I’m a audio engineer working on theaters. Sometimes I work with video projection and wondered if there was a software with which I could stream videos to different network “clients” from my main working space (FOH) while - best case - keeping the audio signal where I am.
Recently, I found casparcg-server in my debian repository and it sounds like this software could at least partly satisfy my needs. If I understand the architecture of carparcg right, I can use a (/several?) server(s) in a network and feed it (/them) with a video-stream from f.e. a laptop on the FOH. Unfortunately, there is no casparcg client in the debian repository, yet. But - as I understand it - the server accepts any ffmpeg-compatible stream, so I could probably even use vlc for that.

Are my assumptions right, so far?
And would a Raspberry 3 or 4 as a server be a possible hardware for recieving a 1080p stream passing it via HDMI to a beamer? (No overlays or realtime effects like fading, etc… Just plain video playback.)
If not, do you know a software which fits my needs?

To understand better, what your goal is: Why would you want to “stream from the FOH”? What do you stream? Do you mean playing some (pre-recorded or pre-rendered) clips in sync to the stage performance on different screens?

Caspar is not too good at accepting video-streams as input, but excels when you play out stuff from it. You could have one or multiple CasparCG servers all around your site, loaded with clips and graphics and control the play-out from your computer via a network connection. Over this connection you only send commands (AMCP is the Caspar command protocol). So no heavy network trafic generated to just play stuff.

So in a “standard” theater setting it is seldom about sending live video to screens, but playing clips on backdrops or the like (or do I understand that completely wrong?). For that Caspar would be a good solution.

That would for sure be a superb alternative to my concept, as the server could be prepared with the needed files before the venue… My concept would offer more flexibility, but I would certainly prefere reliability over convenience.
Streaming from FOH would maybe make it easier to handle audio - as it would certainly be mixed there. But it’s also possible to build a netjack-connection back to the FOH-laptop… (not so heavy traffic as video…)

Is it possible to send AMCP-commands via commandline? This way I could integrate the control over casparcg into other applications, like QLC+, Linux Show Player, etc…

Do these clips contain audio, that is sent to the FOH? In this case I would place the Caspar server (at least the one that has clips with audio, maybe there is stuff on other screens, that is silent) close to the FOH place. Feed the audio into the mixer and send the video via SDI to the projector. SDI signals can travel up to 70m (sometimes also 100m works) on a BNC 75 ohm coax cable. If the distance is bigger, there are fiber adapters, that do not cost a fortune.

Streaming (mostly video, but also audio) has latency, as the signal needs to be encoded and compressed on one end and decoded at the other end. That is not always tolerable in a live setup, so I would go the ‘traditional’ broadcast way with SDI (or AES-EBU or analog for audio) instead of experimenting with streaming.

You can send AMCP commands via Telnet (maybe from the command line, I am a Windows guy). I would use either a dedicated client or Companion, what can control nearly everything, beside Caspar.