Drop mplayer

[mgoral]

For getting FPS we can use e.g. ffmpeg (of ffprobe). For a simple movie playback Qt should do just fine.

[mgoral]

1. After a third try I still don't know how to fetch video metadata with Qt. It seems that it's only
   available if video has been in fact played (e.g. with QMediaPlayer). Otherwise its
   isMetaDataAvailable() method simply returns False. It also seems that installing
   libqt5multimedia-plugins is required to provide a gstreamer-based backend on Linux.
2. Using ffmpeg for fetching FPS is also disputable. First, executing it is actually slower
   than starting MPlayer (on my machine it's 100 ms). It wouldn't be that bad because ffmpeg is
   probably more widespreaded than any movie player, but there is also another issue: it reports
   incorrect, rounded-up FPS, i.e. it rounds 23.976 frames per second to 23.98. It's uncacceptable
   because it would lead to desynchronizing subtitles.

Thinking about this issue is ongoing...

[mgoral]

Regarding reading metadata: use libmediainfo maybe? There doesn't seem to be any Python wrapper for it, so I guess I'll have to show some love for ctypes.

(it also reads subtitle informations so it might be worth checking ;))

[mgoral]

pymediainfo wrapper: https://pymediainfo.readthedocs.io/en/latest/

Although I found on Debian python-mediainfodll and python3-mediainfodll packages too. Haven't tried them yet though.

EDIT:

pymediainfo 2.1.5 is great, we should use it. :D
And for GUI, QMediaPlayer is probably a good replacement.

[mgoral]

Because pymediainfo is easily available on pip and is not present on many systems, this is blocked until Subconvert switches to tox: #71, which should ease up dependency management a little (well, yeah, maybe not for pyqt ;)). It's also required that libmediainfo (C++ library) is present on the system, so that's somethink to think about too.

On the other hand, pymediainfo is just one file, 133 LOC (and MIT license), so for the time being we could just copy it to Subconvert's repository. I hate that, but I'm sick enough of crazy mplayer requirement to do it.