when i run
ffmpeg -y -i test.mov -threads 8 -f webm -aspect 16:9 -vcodec libvpx -deinterlace -g 120 -level 216 -profile 0 -qmax 42 -qmin 10 -rc_buf_aggressivity 0.95 -vb 2M -acodec libvorbis -aq 90 -ac 2 OUTPUT_FILE.webm
it returns an error saying Unknown encoder 'libvpx'
I installed libvpx, libvorbis, libogg, and ffmpeg all via macports
Your configuration of macports was not built with libvpx. Try uninstalling ffmpeg and using Homebrew to install the package instead of macports:
brew install ffmpeg --with-libvpx
or
brew reinstall ffmpeg --with-libvpx
Then your command should work.