ffmpeg support

[sides]

Hey, for personal reasons I wanted to be able to use ffmpeg with this script, so I changed the way encoding is done a bit. This ended up being more massive than I thought, so I figured I'd open this pull request if you're interested, but I understand if it's out of scope.

Outline of changes:

• encode.moon now doesn't build a command to be executed, but instead builds an instance of EncodingParameters which are passed to a backend (mpv or ffmpeg).
• webm.moon, rawvideo.moon, formats/base.moon:
  • Now receive a backend instance in their getX methods.
  • No longer return raw command line options in their getXFilters methods, but instead return an array of MpvFilter (which is up to backend discretion to resolve).
• backends/ dir was added with ffmpeg and mpv. These create their respective commands with varying support. mpv should be producing the same commands as it was before these changes.
• options.moon now has backend and backend_location options.

Some potential benefits from this:

• Add a format for ffmpeg's stream copy (-c copy). This would need a few more changes, particularly in how much control formats have.
• Add an "auto" backend that selects the best one for the current options and playback (so, if you'd select the stream copy format it would select ffmpeg since mpv doesn't have that - if you've enabled ffmpeg in your options).
• Other than that, this was just done for personal tastes.

[ekisu]

Well, that's quite big. It might take some time to look at it, but it seems pretty well structured, at a first glance (a lot better than what I would do, that's for sure).

[sides]

I'm gonna be pushing the changes later today. But just to reiterate, the more I looked at it the more I realized this actually brings pretty little utility (other than to satisfy my autism). It might make adding new options unnecessarily annoying, idk. Anyway, do what you want with it, but you've been warned.

[ekisu]

Well, mpv support for encoding seems to be abandoned (it's there just because it still works), and enabling ffmpeg would allow some extra options (stream copying, two pass, softsubs, etc). And, aside from Windows, usually systems that have mpv installed also have ffmpeg.

[sides]

mpv support for encoding seems to be abandoned (it's there just because it still works)

Didn't know that. Then there might've been a point to this after all. Could also at some point add libav then for those who have that.

Anyway, everything should be almost 1:1 between mpv and ffmpeg now with filters working, except for the "format" filter in raw video that I don't know what to do about. I don't know what the ffmpeg equivalent is and it sort of goes out of my range of expertise.

[ekisu]

Thanks, I'll just do a quick test before merging.

[sides]

@ElegantMonkey uhh, better do a pull again. Those comments in the compiled file are really messing me up.

[ekisu]

Yeah, noticed that. I wish moonc had an option to keep comments.

[ekisu]

Also, hardsubbing and twopass doesn't work (with ffmpeg). I can fix those things myself, so if it's okay for you I'll just merge it.

[ekisu]

I merged it to a branch, to sort those things out before merging into master.