Hi Pudding !
Well, it makes sense, thanks for the clarifications. I think there's an option in sdlmame to display at a multiple of the original size but it obviously reduces the screen size accordingly.
Some people wrote some pixel shader filters to emulate scanlines but I guess they would slow down the emulation on the Pi as they are probably too complex.
Well, thanks, and sorry if my questions sounded stupid
I hope it'll prevent other people from asking them in the future !
Just to stop bothering you and to make sure I got everything perfectly clear : there is no way to implement a PNG mask using pixel shader without signiicant slowdown ; and it's not possible either to apply scanlines + bilinear filtering without the strange current effect ?
Thanks again !