FFMPEG is used from cmdline, switch to the ffmpeg module instead

[rizerphe]

FFMPEG should not be used with the 'subprocess' module because it introduces some problems if, for example, video name contains spaces. It can also cause some issues if the vid name is, for example, vid.mp4; sudo rm -r /home.

Switch to ffmpeg-python or something instead.

[rizerphe]

I'm already working on implementing that in a fork...

[rizerphe]

Pull request added

[Lamaun]

Nice quality improvements. As you can see there are quite many pull requests. The reason is that @carykh doesn't seem to have the time to maintain it and did not react to issue #148 yet.