Okay, not sure what the problem is, but I cannot understand why I’m getting black bars on the right/left of the image? I followed the instructions here. And another problem I’m having is my shader settings don’t seem to load automatically even though I have saved them. I have double checked the file called Retroarch > config > MAME > MAME.slangp and it’s there an updated every time I save. But whenever I restart the game, the shader doesn’t load up and I have to manually load the shader each and everytime.
I also see a configuration override message on the bottom left corner everytime I load a game too. Not sure if that has anything to do with it.
When the shader does work, it has black bars like this which gets cut off.



Did I make that many? 
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