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 1024x768
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 3, 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, and -prescale 3 will triple each pixel. 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.