mpv, Plex for Windows, and Vulkan

Plex for Windows supports configuring its underlying mpv video player via a separate mpv.conf file located at %LOCALAPPDATA%\Plex\mpv.conf (create it if it does not exist). Something one might wanna do is configure it to use Vulkan:

gpu-api=vulkan

However, this alone will actually crash the application once any media is played. Instead, we need to revert gpu-context to its mpv default as well:

gpu-api=vulkan
gpu-context=auto

That is the solution out of the way for those that came here for it; the rest of this page will go into how this was figured out.

Investigation

So let's go back to that first attempt at enabling Vulkan:We are cheating a little here by introducing vo=gpu-next; it is not necessary for Vulkan but it produces a much clearer error message later on which helps to debug the application crash. Without it, the application crashes with no obvious error message in the logs. I just so happened to have this configuration set when I was originally debugging this.

gpu-api=vulkan
vo=gpu-next

Launch Plex for Windows and attempt to play any media. The application will crash, but luckily there are logs, right? Let's check %LOCALAPPDATA%\Plex\Logs\, there are 1–5 log files here and the newest one is Plex.log which should have more information about the crash. Searching for something like "ERROR" might yield multiple results, but we are interested in the last error which should be the one that precedes the crash. That one looks like:

ERROR - [MPVEngine/mpv] vo/gpu-next: Failed initializing any suitable GPU context!

So now let's search the mpv manual; there are a few results for "GPU context", but the most promising one is the gpu-context setting. What is Plex for Windows setting this value to? Is it different from mpv's default of auto? Well, back to the logs:

DEBUG - [MPVEngine/mpv] cplayer: Set property: gpu-context="d3d11" -> 1

Ah, the application is trying to use gpu-context=d3d11 but that does not make sense when we are trying to use Vulkan. So, we revert that to its mpv default and that fixes everything:

gpu-api=vulkan
gpu-context=auto