mpv should be configured with hwdec=yes or hwdec=auto-safe rather than hwdec=vaapi

[Philip Langdale]

(mpv dev here)

mpv has long recommended that users who want hardware decoding start by using `hwdec=auto-safe`. This goes through a set of hwdecs that we consider to be safe, and it will keep trying if the first one doesn't work. So we recommend that Ubuntu uses `hwdec=auto-safe` or `hwdec=yes` (both do the same thing now) in the config file vs `hwdec=vaapi`. This will produce better results on nvidia hardware and also enable the fallback logic which will generally increase the chances of successfully enabling hardware decoding.

[Philip Langdale (langdalepl)]

In fact just putting `hwdec` by itself into the config file implies `hwdec=yes` so that's even more concise.