mame/docs/newvideo.txt

This article originally appeared in a slightly different form at
http://aarongiles.com. You should read this if you are used to how
MAME's video system worked prior to 0.107 and you want to understand
how you should configure MAME with the new rendering system in place.


The New Video Landscape

Since its inception 9 years ago, MAME’s video system has defaulted to 
a mode where it tries to change resolutions on you. And since the 
first port of the core to Windows 5 years ago, it has defaulted to 
using your graphics card to stretch the video to that resolution.

I’m sure a lot of you out there have taken a lot of time to tweak the 
current set of video options to make them work the way you like. But 
every once in a while, you need to take a step back and re-evaluate 
the situation. The current video system has been in place for 5 years 
now without much substantial change. And with the recent rewrite, 
you’re almost certainly going to want to rethink the way you have 
things configured.

At the highest level, there are really three different ways you can 
configure the new system. Placing yourself into one of these three 
categories will help you get the initial settings right. From there, 
you can tweak with the settings to figure out what works best.


Category 1: Bells and whistles. People who fall into this category 
would include anyone with a modern system and a decent video card 
(decent in this context means at least 16MB of VRAM and built in the 
last 5 years or so — we’re not talking cutting edge here). Any decent 
video card will be able to render the simple MAME graphics at pretty 
much any resolution without breaking a sweat. Configure your desktop 
to the video mode you want (preferably something high like 1024×768 
or greater with a high refresh rate, unless you are running on a 
fixed-mode LCD, in which case just match what your LCD panel is), 
and tell MAME to leave the resolution alone. In this day and age, 
there is little reason to switch resolutions at all, unless you 
fall into Category 3, below. In this mode, you will have full access 
to artwork options, and you’ll get your artwork scaled to full 
resolution and with full alpha blending effects. Vector games will 
look crisp, you can use decent fonts, and you can see a whole lot 
more of the world when using the graphics/tilemap viewer. This mode 
uses Direct3D, so you should configure yourself like this:

   -video d3d -noswitchres [-triplebuffer] [-nofilter]

The -noswitchres option tells MAME to just run at the current 
resolution. Although you can let MAME pick a resolution for you, it 
doesn’t really make much sense in D3D mode, and in fact I may even 
remove that feature altogether. To avoid tearing artifacts, I 
recommend using the -triplebuffer option as well. Just make sure your 
monitor’s refresh rate is higher than the game you are running. If 
you dislike the blurry look of the graphics, you can specify the 
-nofilter option to disable bilinear filtering, though that will 
produce blocky artifacts. Alternatively, you can use the -prescale 
option which is described at the end of this article.


Category 2: Like the old days. I really didn’t even want to support 
this mode at all, but certain vocal MAMEdevs would have skinned me 
alive otherwise. People who fall into this category include those who 
have weak systems that worked fine with previous versions of MAME, 
but who don’t run well with Direct3D rendering. (Note that just 
because Space Invaders runs unthrottled at 2000fps with DirectDraw 
and 1000fps with Direct3D doesn’t mean that Direct3D is going to be 
a serious issue when playing at a regular 60fps, so if you’re unsure, 
give the Direct3D route a try for a while.) In this mode, MAME will 
draw the game screen and artwork at the game’s resolution, just like 
it did in MAME 0.106 and earlier; however, some artwork options, 
such as -artcrop, won’t work as you might expect, and some alpha 
blending artwork modes (specifically overlays) will operate with a 
performance penality. MAME will then use your video card to stretch 
the video to the proper aspect ratio.

   -video ddraw -hwstretch [-switchres] [-triplebuffer]

The -switchres is optional here. If your video card is really ancient 
and struggles expanding the screen to fit your desktop resolution, 
you might want to turn it on. Again, to avoid tearing artifacts, I 
recommend using the -triplebuffer option as well, but make sure your 
monitor’s refresh rate is higher than the game you are running 
(-switchres will do that for you if you use it). If your video card 
produces blurry pixels which you don’t like, try the -prescale option 
described at the end of this article.


Category 3: Anal video mode types. These are the guys who have 
generally built their own cabinets and set them up with a CRT display 
where they have several dozen carefully hand-tweaked video modes that 
approximate the original video modes the games ran at. They want MAME 
to pick that hand-tweaked mode and use it, drawing one pixel on the 
screen for each pixel in the original game. They don’t give a whit 
about artwork or anything other than the raw pixels going to the 
right place. Fortunately, you can still configure MAME for this case 
as well:

   -video ddraw -nohwstretch -switchres [-triplebuffer]

Obviously in this case, the -switchres is required. You also want to 
disable hardware stretching, otherwise you won’t get that “perfect” 
1:1 pixel mapping. Triple buffering may or may not help.


So, I recommend starting with these initial options and then tweaking 
from there. One additional option you might want to try in 
combination with the above is the -prescale option. -prescale takes 
an integer parameter from 1 to 8, and specifies a magnification 
amount by which the screen pixels are expanded before they are drawn 
to the screen. Why is this useful? And how much of a performance 
impact does it have? Well, that depends on the mode you are running 
in.

If you are running in Category 1 (-video d3d), then -prescale will 
use your video card to scale the game graphics up before rendering 
them to the screen. Depending on the video card, this is usually a 
small performance hit, but not too significant. The benefit is that 
each prescale factor reduces the blurriness of the pixels. 
-prescale 1 is the default, which does no scaling. -prescale 2 will 
double each pixel, -prescale 3 will triple each pixel, etc. For my 
money, -prescale 2 is sufficient, but people with super high 
resolution displays claim that larger -prescale factors work even 
better.

If you are running in Category 2 (-video ddraw -hwstretch), then 
-prescale will cause MAME to compose the screen graphics at the 
specified scale factor. This is unfortunately done in software, but 
carries the benefit that artwork, fonts, and the graphics viewer can 
take advantage of the additional resolution to produce nicer results. 
The end effect is that you will get less blurry pixels, just like the 
Category 1 case, plus higher quality artwork, fonts, and more visible 
area in the graphics viewer.

If you are running in Category 3 (-video ddraw -nohwstretch), then 
-prescale will cause MAME to pick a video mode that is the prescale 
factor times the raw screen resolution, and then MAME will, in 
software, compose the screen graphics at the specified scale factor. 
This has all the advantages of the Category 2 case, except that since 
there wasn’t any pixel blurring to begin with, there is no additional 
crispness that comes about as a result.

Finally, you may be wondering about effects (and yes, scanlines are 
an “effect”). Effects are no longer hard-coded into the system. 
Rather, you can provide a PNG file in the artwork directory that will
be loaded and overlaid on top of screen bitmaps. See the description
of -effect in windows.txt for more details.