Support for fractional Pixel Aspect Ratios

[sdsnatcheralpha@…]

Many computers and video-games from the 80s/90s had fractional Pixel Aspect Ratios, but currently GrafX2 only supports integer ratios.

For example:

• CGA and VGA 320x200: 1:1.2
• CGA 640x200: 1:2.4
• EGA 640x350: 1:1.371
• MSX1/2/2+, ColecoVision, NES, SNES: 1.138:1
• Sharp X68000 512x512@31kHz: 1.44:1
• Sharp X68000 512x512@15kHz: 1.28:1
• Sharp X68000 768x512@31kHz: 0.96:1
• Commodore 64 NTSC: 3:4

Reference: ​Dot clock rates

[Thomas Bernard]

well that's an issue of your video card, not GrafX2.
In fact the DOS version of GrafX2 did support a wide range of modes, like 320x200, 320x240, 320x256, etc. but now we are limited by what's supported by SDL.

[sdsnatcheralpha@…]

Wouldn't it be possible to use SDL/openGL to do the fractional aspect ratio adjustment, like many emulators that use SDL do?

[PulkoMandy]

The recommended way to achieve this for GrafX2 is to setup appropriate video modes at the OS level. On Windows you can use PowerStrip, on Linux you need some tool to create appropriate X11 modelines (you can use xvidtune to experiment with those).

Once added to the system, these will be handled fine by SDL.

On CRT displays and with the "double" setting in GrafX2 video mode selector, you can get quite accurate rendering of these video modes, much better than what the openGL scaling could achieve. On LCDs, well, it depends on your hardware, but whatever you try it's not going to be very accurate anyway.