Answer by pje for How do I convert a video to GIF using ffmpeg, with reasonable quality?

As of ffmpeg 2.6, we can do even better. Based on High quality GIF with FFmpeg:

palette="/tmp/palette.png"filters="fps=15,scale=320:-1:flags=lanczos"ffmpeg -i input.flv -vf "$filters,palettegen" -y $paletteffmpeg -i input.flv -i $palette -lavfi "$filters [x]; [x][1:v] paletteuse" -y output.gif