Before you can build mpv.app on an M1 Mac, there's a couple of required dependencies you'll need to install if you haven't already:

1. If you don't have the Xcode Command Line Tools installed, run xcode-select --install and select Install on the prompt that appears.

2. If you don't have Homebrew installed, follow the instructions here.

3. If you've never run brew install --only-dependencies mpv, do so now.

You'll also need a local copy of the mpv repo, which you can get by running git clone https://github.com/mpv-player/mpv.

You can now run the attached script to build mpv.app on an M1 Mac yourself. Just make sure you're in the root directory of the cloned repo before doing so so.

Going forward, you can update your local copy of the repo by running the following commands from its root directory:

git reset --hard
git clean --force -d -x
git pull origin master