Trying to add an option to avoid live RetroArch geometry adjustments

[vanfanel]

Hi there @realnc

Live RetroArch geometry adjustments cause major audio drops on Raspberry Pi3-4 and other aarch64 light computers.

In order to avoid live RetroArch geometry adjustment AND have the right aspect ratio for non-4:3 games, I am working on trying to add an option to have games with 16:10 ratios displayed letterboxed inside the default 4:3 screen area.
For example, Jazz Jackrabbit should look like this, letterboxed inside the 4:3 area:

...it would be smaller, but live geometry adjustment could be avoided by always keeping the same 4:3 aspect ratio.

I have started by disabling live RetroArch geometry callback adjustment here:

dosbox-core/libretro/src/libretro.cpp

Line 305 in 3acbd34

static void update_gfx_mode(const bool change_fps)

...but doing that alone, Jazz in-game levels seem vertically stretched to 4:3, instead of letterboxed inside 4:3 with a 16:10-like aspect ratio as in the picture I put up there.

So, where in the DOSBOX code should I try to do ajustments to get it done? Do you happen to know?

[biffrapper]

Original DOS games were never letterboxed. They were always stretched. 4:3 320x200 is not supposed to, nor ever was pixel perfect square pixels. Ever. Games were designed and meant to be played 4:3 stretched.

[vanfanel]

Original DOS games were never letterboxed. They were always stretched. 4:3 320x200 is not supposed to, nor ever was pixel perfect square pixels. Ever. Games were designed and meant to be played 4:3 stretched.

Wrong. Some games had oddball aspect ratios:
https://www.vogons.org/viewtopic.php?p=384596#p384596

In fact, they set these aspect ratios on DosBOX-core, too, so they display in "wider" aspect ratios.
Try Rusty intro scenes, too. And there are many more.

[biffrapper]

I'm not wrong, as I grew up in the 70s and 80s playing games on various PCs and consoles, from the Atari, PCs in CGA/EGA/TGA/VGA/etc. on many different monitors and formats. Everything was 4:3. Exceptions being stuff like the Amiga which would output letterboxed stuff, mainly due to NTSC games being run on PAL monitors that supported both formats, as NTSC had less lines.

Anything that was NTSC, however, or in the USA was 4:3. PAL native games were also 4:3 on proper, native equipment.

320x200 and 320x240 were both shown at 4;3 on a CRT. Likewise 640x200, 640x400, 640x480 and even 800x600 were also shown... at 4:3.

The monitors would automatically adapt their scanning patterns to fit within a 4:3 field. This is not wrong, this is simply how things worked back then on original hardware.

[vanfanel]

@biffrapper I gave you actual pictures of Jazz Jackrabbit running on a CRT.
What else do you need?