MAMEWorld Forums - EmuChat - Re: Recording pixel-perfect videos via MAME.

> it's not a bug, MAME shows you the default resolution of the video chip, in some
> cases the chips can be reprogrammed to display different modes (think how many modes
> your PC can display)

"Default resolution" is essentially an arbitrary choice, and not used by all MAME drivers. I think "maximum resolution" or even "maximum bandwidth" might be a more appropriate standard for screen configuration, but those might be rather misleading for systems with ludicrous hi-res video modes which are only very rarely used, such as the ECS Amiga's 1280x256.

> hard truth is the concept of a 'resolution' is nowhere near as simple as it might
> seem, some games use multiple resolutions on different lines of the same screen, some
> different layers (think Galaxian and its starfield)

Galaxia is more problematic than Galaxian in this regard, since the hardware's video circuits have dot clocks that aren't even multiples of each other. The MAME driver fails to properly account for this, which is why the game runs too fast.

> the modes people
> talk about are a massive over-simplification that MAME has perpetuated over the
> years.

Here's one further wrinkle. MAME's current model for emulating CRTCs is to take the software-programmed parameters and try to make a screen mode out of that. This works most of the time for switching screen modes, but there are some programs that engage in serious CRTC abuse, rewriting the parameters many times per frame. Some BBC Micro games do this, and the (currently unemulated) QVT-201 video terminal appears to implement smooth scrolling this way.