Improve mpv playback configuration

README.md

@@ -36,6 +36,22 @@ Once running, you should be able to access the UI via http://localhost:8080.
 
 QueueCube supports video as well. Just set the environment variable `ENABLE_VIDEO=1`. 
 
+When video is enabled, QueueCube starts a managed `mpv` process. The process
+fullscreens by default; set `MPV_FULLSCREEN=0` to leave sizing and placement to
+your window manager. These optional environment variables are also passed to
+`mpv`:
+
+| Environment variable | mpv option |
+| --- | --- |
+| `MPV_WAYLAND_APP_ID` | `--wayland-app-id=...` |
+| `MPV_TITLE` | `--title=...` |
+| `MPV_BORDER` | `--border=...` |
+| `MPV_ONTOP=1` | `--ontop` |
+| `MPV_YTDL_FORMAT` | `--ytdl-format=...` |
+
+For less common options, `MPV_EXTRA_ARGS` can contain additional shell-style
+arguments that will be appended to the generated `mpv` command line.
+
 #### Video + Docker
 
 When running in a Docker container, there are a few extra steps needed to make this work. 
@@ -68,4 +84,3 @@ privileged: true
 (or `--privileged`). 
 
 On Podman rootless, it seems to be enough to just run it with the "unconfined" security profile (`seccomp=unconfined`). 
-