Picture in picture encoder

Basicly, we want something that does what we currently do using OBS studio:

• define position, size and origin for data sources: background image, camera, slides and logo image
• define streaming targets: rtmp servers, ...
• ingest from something running on the video boxes (mistserver, ffmpeg, a thin wrapper around ffmpeg, whatever...)
• create a fixed picture-in-picture from this, like https://www.youtube.com/watch?v=YQJUlUdQfZc
• push this PiP stream to a decent external

It would be really really useful to get visual feedback on the video box lcd screens:

• (wall clock timestamped) (snapshots from) the picture-in-picture stream
• ? (PiP stream) audio volume
• current date
• box ip adress