More adequate framerate for modern displays

[vanfanel]

Hi!
Since OpenTyrian's main advantage over original DOS executable is being able to play Tyrian on modern systems, which are ~60Hz over HDMI for the most part, and since OpenTyrian currently targets origina Tyrian farmerate (35FPS, based on a 70Hz display), I believe it would be a good idea to add a 30FPS mode, or even a 60FPS mode, that would fit well on modern displays.

I have been investigating the OpenTyrian sources myself: the SDL_Delay() calls used for framerate control are in src/nortsong.c.
However, this is pretty much obscure to me:
float jasondelay = 1000.0f / (1193180.0f / 0x4300);

and also setdelay(), setjasondelay(), setjasondelay2()... seem to use different target, target2, etc.. variables.
So, for experimentation, what could I mangle with to force the game into 30FPS instead of 60FPS?

Additional note:
To get smooth scroll, the SDL_CreateRenderer() call must be like this:
main_window_renderer = SDL_CreateRenderer(main_window, -1, SDL_RENDERER_ACCELERATED|SDL_RENDERER_PRESENTVSYNC);

So only framerate adjustment remains! Ideally, the game should sync to video (uncapped framerate) while keeping it's original speed (movement interpolation of some kind... but ~30 FPS should be an improvement over how ugly current scroll looks on modern screens).

[carlreinke]

Like many games of its era, the frame rate in Tyrian is tied directly to the gameplay. (Changing the game speed in the in-game menu also changes the frame rate.) Decoupling them would require rearchitecting the whole game, which is unlikely to ever happen.

[vanfanel]

@carlreinke Ok, but here must be some variable or value I can tweak on src/nortsong.c so I can get a 30FPS framerate instead of 35.

[vanfanel]

Anyway, do you know what these values mean, please?

float jasondelay = 1000.0f / (1193180.0f / 0x4300);

[carlreinke]

1000 is 1 second in milliseconds. 1,193,180 Hz is the frequency of the timer available on DOS PCs. 0x4300 is the number of timer cycles per tick in Tyrian.