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Describe the bug
A clear and concise description of what the bug is.
Tuna cant grab album art if its not in the audio file metadata, I've only tested MPRIS.
Suggesting to make Tuna try and grab cover art from an image that is in the directory where the music is played, like how most media players do if it can't find the image in the file metadata.
And if possible grab the image from MPRIS data (not sure if thats possible?)

To Reproduce
Steps to reproduce the behavior:
Play a song without art in the metadata and is instead in the directory of where the music is being played. Use a MPRIS compatible media player.
Connect it to Tuna.
Make an image source in OBS and point it to the cover art file tuna makes.
Placeholder image appears.

Expected behavior
A clear and concise description of what you expected to happen.
The album art to show.

Screenshots
If applicable, add screenshots to help explain your problem.

How it looks on the music player and where the cover art is:

You can see it has no trouble grabbing it even if its not in the metadata.

Example of what Tuna currently does (grabs the image from the file metadata as seen in the file thumbnails):

Log
Add the link to your entire obs studio log

https://obsproject.com/logs/SrzHq71YO5QzODaM

Also add the entire crash report, if this issues is about a crash.

Additional context
Add any other context about the problem here.