Reduce Generated GIF Size Using FFMPEG

I'm developing android application that converts mp4 files into gifs using ffmpeg. Problem is that generated gifs are huge in size. And another problem is that I can't use anything else than ffmpeg(e.g.imagemagick for convert, or even palletes for now) to reduce generated gif size.

this is the command I'm using: ffmpeg -y -i file.mp4 -pix_fmt rgb24 -r 10 -s 320x480 file.gif

So is there any other way to optimize conversion?

The standard way to use ffmpeg for GIFs is

Generate a palette from the video

ffmpeg -y -i file.mp4 -vf palettegen palette.png

Then,

ffmpeg -y -i file.mp4 -i palette.png -filter_complex paletteuse -r 10 -s 320x480 file.gif

More options documented here.

I tried all these techniques and I ended up using https://ezgif.com

I have no idea what magic they're using under the hood, but their compression level knob, palette optimization and resolution reduction resulted in the highest visual quality and smallest file size.

I tried -vf palettegen and -filter_complex paletteuse but that removed the ability to -vf "scale=iw*.2:ih*.2" in the same run so I had to do that separately. And ffmpeg created larger files for 0.3 scale than 0.5 which is odd. After an hour of fiddling, I tried ezgif and it worked nicely.

vid=       
start_time=00:00:01
duration=5       
height=ih/2      # input height halved , can replace with pixils . 
width=-2         # keeps aspect ratio . can replace with pixils . 
fps=25           # frames per a second .

filters="fps=$fps,scale=$width:$height:flags=lanczos"

ffmpeg -ss $start_time                             \
       -t  $duration                               \
       -i  "$vid"                                  \
       -vf "$filters,palettegen"                   \
       -y  palette.png                             &&
ffmpeg -ss $start_time                             \
       -t  $duration                               \
       -i  "$vid"                                  \
       -i  palette.png                                \
       -lavfi "$filters [x]; [x][1:v] paletteuse"  \
       -y  "$vid".gif                              &&
rm palette.png 

link to documentation

more info