Toolbox

ffmpeg recipes

You can find the ffmpeg documentation here. I have it installed on macOS with brew install ffmpeg.

Compress a screencast

Full-screen screencasts recorded with QuickTime tend to be on the large side. We can use ffmpeg to obtain a smaller file size by simply converting it to MP4:

ffmpeg -i my-recording.mov my-recording.mp4

(For example, it brought a 40-second screencast from 38MB down to 4.5MB)

Screencast to GIF

There are many ways to turn a video into a GIF with ffmpeg and other free tools.

The straightforward way is to:

ffmpeg -i my-recording.mov -pix_fmt rgb24 output.gif

Note that recent versions of ffmpeg, such as the v4.2.2 I'm on at the time of writing, can convert a video to a GIF without having to specify -pix_fmt rgb24.

A few useful parameters to include:

The example below outputs a 320 × 240 GIF with 10 frames per second:

ffmpeg -i my-recording.mov -r 10 -s 320x240 output.gif

The -s parameter distorts the input video to fit the specified size. If instead you want to maintain the original aspect ratio, use the scale filter, to which -s is actually a shortcut, directly:

ffmpeg -i my-recording.mov -vf scale=320:-1 output.gif

Use -1 as auto when specifying the scale.

To speed up the video, use the setpts filter:

ffmpeg -i my-recording.mov -filter:v "setpts=0.5*PTS" my-recording-sped-up.mp4

The command above makes an MP4 video at twice the speed of the original MOV. For some reason I couldn't apply the setpts filter in a direct MOV to GIF pipeline, so I'm first making a sped-up MP4, then converting that to a GIF.


This method tends to output poorer-quality GIFs. A more complicated solution is explained in this answer on the Super User StackExchange, along with an article detailing how to obtain better-looking GIFs from ffmpeg.

This gist walks you through creating a GIF with ffmpeg and gifsicle.

See also this article from GIPHY Engineering.

Looping a video N times

The -stream_loop N option lets you loop (concatenate) the input video N times. In the example below, we generate output.mp4 which is twenty times the length of input.mp4.

ffmpeg -stream_loop 20 -i input.mp4 -c copy output.mp4

Note: This didn't work with the ffmpeg version I had on my machine, so it's best to always keep the program up to date.