Animated gif writer via ffmpeg

[almarklein]

As mentioned in #219, ffmpeg can also export animated gif (ffmpeg 2.6+). Would be a nice addition. http://blog.pkh.me/p/21-high-quality-gif-with-ffmpeg.html

Advantages are speed and maybe quality, we'd have to do some testing to see how the paletting related to PIL's paletting. Disadvantage is that it needs the ffmpeg exe, which is not available by default (though easy enough to install using one function call).

[almarklein]

Also see #115

[FirefoxMetzger]

The pyAV plugin I am writing supports filters, so this should - in theory - be possible.

In practice, it depends on me figuring out how to send an EOF signal to palettegen, which is the FFmpeg filter that does all the magic here. See PyAV-Org/PyAV#886 for details.

Edit: Note that this only affects the global palette. Generating single palettes (using palettegen with stats_mode=single) works fine.

[FirefoxMetzger]

I submitted a PR to pyAV a few days back that allows sending EOF to a filter, so we will be able to use palettegen with the next pyAV release. From this point on it should be possible to generate GIF via ffmpeg, too.

[FirefoxMetzger]

pyAV released v9 recently which includes my changes to send EOF to filters (among other goodies). I've updated our pyAV plugin, and now we can indeed create GIF using ffmpeg (that use an optimized global palette):

(at the moment it's grayscale only until I work out how to handle frames with palette in pyav)

[FirefoxMetzger]

And now we can do colored GIFs, too: