This is a 3rd party tap for Homebrew. It provides the same formula for libplacebo as in core, but with the option of installing the nxtedition-fork by providing the --HEAD option.
In order to use this tap, you need to install Homebrew.
Then, to run a default installation, run:
brew tap nxtedition/libplacebo
brew install nxtedition/libplacebo/libplacebo