Multiple side-to-side video streams in one file without transcoding

Question

I am investigating a possibility to store video streams which are coming from few sources already coded in h264 without video transcoding as the device I would like to use f

Answer 1

Just specify multiple inputs.

ffmpeg -i [input 1] -i [input 2] ... -map 0 -map 1 ... -codec copy -f matroska [output]

As for the "side-to-side" part, it's up to the player to determine the presentation. If you don't control the player and you need a specific layout or presentation, then you must "burn" all these video streams into a new one and encode it as a new single stream.