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F )   S o l v i n g   o v e r s c a n   a n d   g e o m e t r y   i s s u e s

As a previous note, be aware that we always recommend the usage of monitors with adjustable geometry settings. Most will have them, but for many TV sets it'll not be easy to get access to the service menu or the devices which control them. Arcade games (and many old PC games) were conceived for monitors with easy-to-control screen geometry, so it wasn't really important which model or video mode they used and the consequent variations in screen geometry parameters against other samples (position, borders, etc.). Therefore, you can't expect a universal solution by software which sets a perfectly adjusted visible area on screen for every game in MAME so that you won't ever need to make monitor tweaks. Super resolutions (and only super resolutions) will essentially get the same horizontal amplitude for all the games, but you'll need to manually adjust the vertical size if you want to properly display games with different-enough video modes, though we'll show a way here (two ways, actually) to control the vertical position by software in case you want to leave at least that monitor setting intact.

F.1) Setting the best monitor specs

Different monitors require different definitions for the monitor's specifications in our system, and it's the monitor specs what determines overall screen geometry. Through Video Mode Maker, a definition of monitor specs was set in the process of installation; it's located in the Monitor settings tab, and it can be changed by another preset and even edited at will. It's likely that with the default preset you don't get a perfectly centered area under your current/default monitor parameters, so you may start by editing the monitor specs.

If you'll be using the monitor also with devices other than the PC for emulation (say, a game console), a smart approach may be firstly adjusting the monitor parameters to get the best geometry for these devices, given that they'll normally won't give you the option to do it internally.

In order to edit a preset (the one named Arcade 15.7 kHz - standard resolution is generally a good one to use as the basis for 15-kHz monitors, including TV sets), you need to know well what a monitor specs line consists of, which is widely explained here. Usually, you'll just need to correct the horizontal position, so take a look at this example:

15625-16200, 49.50-65.00, 2.000, 4.700, 8.000, 0.064, 0.192, 1.024, 0, 0, 192, 288, 448, 576 (original Arcade 15.7 kHz preset)

15625-16200, 49.50-65.00, 2.000, 4.700, 6.000, 0.064, 0.192, 1.024, 0, 0, 192, 288, 448, 576 (edited Arcade 15.7 kHz preset)

By picking the aforementioned preset in the corresponding field and changing this value with Notepad when clicking the edit button in VMM, you'll center the picture horizontally according to the demands of most NTSC consoles on many Trinitron TV sets, so you won't need to enter the TV's service menu and adjust this setting every time you change from your PC to your consoles and viceversa.

If, for instance, you also get the image positioned too low, you'll need to reduce the vertical back porch value:

15625-16200, 49.50-65.00, 2.000, 4.700, 6.000, 0.064, 0.192, 1.020, 0, 0, 192, 288, 448, 576

And so on.

Given that you can export the defined monitor specs directly to Groovy MAME as explained before, you don't need to also define this in Groovy MAME's INI file, though you can do it if you want to for some reason by finding and editing this line:

monitor                   generic_15

Yet more presets here.

Much like with VMM, it's possible to set custom values by the monitor's particular specs. To do that, type custom in place of generic_15 and add the values in the crt_range lines accordingly, taking always as a reference one of the given samples and their effect. Check VMM's tutorial for further elaboration.

F.2) Tuning up the screen geometry in a per-game basis

Groovy MAME lets us define the modeline(s) in the machinename.ini files, overriding the definitions in MAME's INI file. This is extremely useful to solve particularly geometry problems, such as the vertical centering derived from the disparity of the vertical scan rates or the overscan-into-underscan issues in quite a few arcade games.

The easiest way to tweak modelines per-game is:

1. Run the game with verbose enabled: Start menu, Run, C:\GROOVYMAME\mame64.exe machinename -v

2. Exit Groovy MAME and launch Arcade OSD. You'll notice the Get mode from clipboard option is enabled, go there. It will launch the last mode used by Groovy MAME, including custom timings.

3. Make the geometry changes as desired. Remember that you can't modify the vertical amplitude by software. 

4. When done, select Back and Copy modeline to clipboard. Exit the program.

5. Open Notepad, press CTRL + V. Now copy to the clipboard the modeline line, not the CRT range line, and paste it in your machinename.ini:

modeline "2560x240_60 kHz Hz" PixelClock, HRes, HSyncStart, HSyncEnd, HTotal, VRes, VSyncStart, VSyncEnd, VTotal, hsync, vsync

6. Save changes and test the game/machine.

Notes:

- Regarding the modeline option, the only requirement to use it is to have a modeline already available in the system with the same active width and height.

- Groovy MAME keeps the video mode specifications if modeline is used, but if the mode is defined with resolution instead, Groovy MAME will not use the vertical refresh attending Arcade OSD, but attending the emulator's request for that game, if v-sync is not disabled. The picture won't be scaled if it doesn't match the defined resolution (black borders and some shift will appear).

- If resolution is used, the video mode displayed in-game through MAME's menu and splash screen shows the vertical refresh from A-OSD according to that label, which usually won't be the one in actual use for the reason above.

- For minor tweaks, MAME's Slider Controls (reach them also through the TAB menu when running a machine), allows to modify the screen's horizontal and vertical position.

G )   E x t r a   t i p s

Calamity also provides us with the following advices for some particular situations:

G.1) Improving performance on games with switching resolutions

Windows 7's video stack adds an absurd overhead to video mode switching -- it's something you're not supposed to do so often in normal applications. With regards to games that dynamically witch resolutions, there are some things that can be done to avoid issues:

- Disable the changeres option in mame.ini. This will leave the game all the time at its default resolution, the one that's reported by MAME's XML. There'll be a single mode change on load, then no in-game mode switching. The problem with this is yhat, very often, the resolution reported is the first one assigned by the hardware initialization, which doesn't match the main video mode used by the game.

- Force a given resolution by means of the resolution option. This by itself will disable mode switching (same as nochangeres) but you can specify the main video mode that's actually used during the game.

- Use super resolutions. By using super resolutions, most mode changes will be unneeded. Only vertical resolution changes will trigger an actual video mode change. This is ideal for some systems (such as Sega Mega Drive) which change horizontal frequency quite often while leaving vertical unchanged. For systems that also change vertical resolution, the previous method is preferred.

Besides this, follow these recommendations when possible:

- Try to keep the mode list as short as possible; this will make mode changes work faster. Super resolutions will be of help here.

- Only enable the outputs you actually use. Each extra output that's enabled exponentially increases the time required by certain graphic API calls (e. g. EnumDisplaySettings).

- Use your frontend as your system shell (instead of explorer.exe). Having the default shell at the background means that upon a mode change, Windows will send messages to all the little things that live on your desktop, asking them to redraw themselves etc., which takes a lot of time.

G.2) Forcing single scan on games with double-scanned graphics

This comes in handy, for instance, with the systems where MAME mistakenly reports a vertical resolution which doubles the native one. Let's illustrate this with MSX 2 computer series emulation -- MAME always reports a vertical display resolution of 466 pixels for most MSX2/MSXP games, but, in actuality, MSX 2's Screen 5~7 modes displayed either, single-scan (233 lines) or interlaced (466 lines), and very few games used the interlaced modality (and those which did, only used it at some very particular moments). So, when emulating these games on a 15-kHz monitor, the correct approach consists in getting progressive modes of 233 lines instead of the interlaced mode at 466 lines, which, if anything, should only be called at those moments to make the change dynamically.

Until MAME fixes it in the driver's code, other than hardware de-interlacing, this can only be achieved by installing a super wide resolution of 233 lines in this case, setting it through machinename.ini and the resolution command, and also setting cleanstretch 2.

(Note: From Groovy MAME 0.177 onwards, cleanstretch options are no longer used, so set -ues (unevenstretch 1) in machinename.ini. This is required so fractional stretching is forced. We need to apply a fractional scale factor of 0.5 to the vertical axis. Integer subscaling is not possible since the minimum possible integer factor is 1. The trick to avoid scaling artifacts is to choose a resolution whose height is the exact half of MAME's reported resolution (466). The width is not a problem because we have a super wide resolution.)

Using nochangeres 1 is recommended too if the emulated system makes constant resolution changes, as these make the emulation too slow.

End of the guide