Multi-Source streaming Setup
Streaming more than one input source can probably be done in several ways. I will try to two different ways to stream the input of several PCs using one central “Streaming PC”. The first option can only be used if all input creating sources are located near the streaming PC and can be connected using a video cable, as in my example HDMI cables with a splitter combination. Option two can be done local but also over the internet. The streaming PC will grab the sources off a server, enough bandwidth assured, which can also run on the streaming PC. In this case all sources have to be able to create a rtmp stream themselves. I use PCs in both examples but you can exchange them with other devices for option 1. For option 2 this is limited by the rtmp streaming capabilities of your sources. (Consoles would each need their own streaming PC for example)
Local setup (using Video connection and splitters)
One problem you might encounter when using a switches: (thanks to mrasmus for pointing it out) If you switch away from Device1 to Device2 on your switch, the PC connected as Device1 will think there is no more Monitor connected to it and will likely temporarily blacken the screens (also the gaming Monitor for example) while Windows turns off this Monitor. And when you switch back it has to reactivate the Monitor and the Windows on Device2 will deactivate its.
The Streaming PC needs to be able to receive those streams, for example watch them through vlc or a browser window. It needs a download speed that is able to receive the number of streams you want to include while the download only has to suffice for one “final” stream.
Nginx for example is a good Server software which can be compiled with the rtmp module to work as a streaming server. In a Virtual Machine or as an extra PC it would receive all streams and you could grab them and include them to one stream.
These are not Studio grade setups, but they will work if you set everything up correctly. So if you ever wondered how to stream 2 or more sources, this could be a cheap way for you to do it.
I will probably not be able to answer all server related questions, but if you have setup related stuff, just post your question below. And if you found a mistake or know of a different way, also post it below or message me.