I would like to know which is the best or the most efficient library to concatenate video files. I'm working in a Rails project and I need to merge different video files to get one video in mp4. I've been searching in Internet but I don't see a clear and easy solution. So if you could give a good advice I would really appreciate it.
Your best choice might be FFMPEG
You will be able to manipulate video input and audio as well as many other things, and for the concatenation you could use the following
system "ffmpeg -i concat: \"#{video source(path)} | #{other video source (path)}\" -c copy #{name_of_output_file}"