Convert an animated GIF to an MP4 with ffmpeg

• Posted 10 July 2024
• Tagged with ffmpeg

I sometimes need to convert animated GIFs into MP4 movie files – this can often result in much smaller files, which is useful for serving the images on the web.

This is the ffmpeg command I use:

ffmpeg \
  -i INPUT_GIF_PATH \
  -movflags faststart \
  -pix_fmt yuv420p \
  [-vf scale=WIDTH:HEIGHT] \
  [-y] \
  OUTPUT_MP4_PATH

Here’s what it’s doing:

• -i INPUT_GIF_PATH is the path to the animated GIF I want to convert

• -movflags faststart does something to move the metadata around in the file. I’m not sure what the benefit of this is; it’s been in my copy/pasted version of this code for years.

• -pix_fmt yuv420p is choosing a pixel format. I’m not entirely sure what this is doing of why yuv420p is the value I should be using, but if I omit it, the videos don’t work in QuickTime Player or Safari.

• -vf scale=WIDTH:HEIGHT set the dimensions of the final video. If I omit this, the MP4 is generated at the same dimensions as the original GIF.

  There’s some subtlety to this I don’t understand yet. I was converting a 600×660 GIF to a 363×400 MP4, and I got an error in the conversion process:

  width not divisible by 2 (363x400)
  

  According to Stack Overflow, this is because H.264 requires even dimensions. Tweaking the desired width so it was even seems to fix this.

• -y tells ffmpeg to overwrite the existing file, if it already exists. If you don’t provide this flag and the file already exists, it presents an interactive prompt:

  File 'out.mp4' already exists. Overwrite? [y/N]