This is a relatively low level helper plugin for video transcoding with ffmpeg. You generally shouldn't need to use this.
You're most likely looking for gatsby-remark-videos if you want to automatically convert videos in your markdown, or gatsby-transformer-ffmpeg if you're looking to use these videos elsewhere in your website
npm install --save gatsby-plugin-ffmpeg
ffmpeg with the correct codecs is also required.
With Homebrew 2.0.3/ffmpeg 4.1.1 ffmpeg options are no longer available on the default tap.
The following will install ffmpeg.
brew tap varenc/ffmpeg brew tap-pin varenc/ffmpeg brew install ffmpeg $(brew options ffmpeg --compact)