I prefer tools like https://asciinema.org/ when I want to show terminal tricks and cli tools I build, but sometimes you need to show something that breaks out of the terminal. In this case I record a .mov screen cast using quicktime then do several transformations using ffmpeg to get a small uploaded web friendly .webm file.

1. cut down the video if need be

$ ffmpeg -i movie.mp4 -ss 00:00:03 -t 00:00:08 -async 1 cut.mp4

2. scale down the .mov file to something more web friendly

$ ffmpeg -i vim_dic.mov -filter:v scale=512:-1 -c:a copy vim_dic_small.mov

3. convert the .mov to .webm

$ ffmpeg -i vim_dic_small.mov -c:v libvpx -crf 10 -b:v 1M -c:a libvorbis vim_dic.webm

If you don’t have ffmpeg is available via brew

source:

• brew ffmpeg
• convert mov to webm
• resize mov
• html video element
• cutting video