To get an animated gif from a movie, I do this:

ffmpeg -i themovie.mov themovie-%02d.png
convert -verbose +dither -layers Optimize themovie*.gif GIF:- > themovie.gif

convert comes from ImageMagick. I could/should pass some more stuff to ffmpeg and convert, such as -s to resize and -r to change FPS of the PNGs, or -resize to resize the output gif.

More info in this gist.

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via blog.vucica.net