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[quote=97150]How to get perfect video scaling

On a fixed-pixel display, you have to stretch the native resolution of a game by a whole integer amount, otherwise you will get ugly scaling artifacts; some pixels will be larger or of a different shape than others. Scaling artifacts are particularly noticeable when a game is scrolling, and they ruin the look of scanlines. To eliminate scaling artifacts, do the following:

1. Hold “x” or “m” when launching a game to bring up the launch menu. By default, “video mode” should be blank. If it is not blank, select “remove video mode choice.” This will tell Retroarch to automatically detect the native resolution of your display.
2. Now scroll to “retroarch render resolution.” Set this to “use video output” if using a raspberry pi model 2. Otherwise leave as is (640×480).
3. Launch game.
4. go to RGUI -> settings -> video settings -> integer scale ON
5. RGUI -> options -> video options -> set custom ratio
6. Set to whatever looks best. You can’t get to a perfect 4:3 aspect ratio but you can get close if you use the right scaling ratio. For NES for example, 6×5 scaling gets you close to a 4:3 aspect ratio with the top and bottom cropped off (see below)

A note on 5x scale: If you use 5x scale and wish to use a scanline overlay, you need to use one designed for 5x, which I’ve provided here. It is desirable to set the Y axis to 5x scale for many systems, cropping off the top and bottom of the picture. On a CRT, the “safe area” was 90% of the picture. The safe area was the zone in which important graphics were displayed. The rest was occupied by overscan, which wasn’t meant to be displayed and which was cropped off by CRTs. With 5x scale on the Y axis, or 1200 pixels, you are cropping off 120 pixels on a 1080 display. This is 24 pixels on a 240p console, or 10%, equivalent to the entire overscan area.

Important Note: depending on the core, crop overscan may need to be turned either ON or OFF. Crop overscan can cause problems with scaling if not set right.

Note: these resolutions are for a 1080p display.





More systems will be added as they are tested.


patrickm, could you please provide your recommendations for, PSX, Mastersystem, PC-Engine as well? Sega CD seem to differ from genesis and 32x as well.