AV Guides, Howto & Guides
Gefen VGA to DVI Scaler Plus and XRGB3
Update 4th April 2014 – Added input lag times.
Update 21 June 2012 – Changed the update about V-sync due to new research/evidence.
Update 23 Feb 2012 – Added a paragraph about the lack of a V-sync option under “Known problems”.
Using an XRGB3 on modern displays can be something of a hassle. Compatibility with the XRB3 is very hit and miss with modern sets, you may simply see the dreaded “unsupported signal” message, assuming your TV manufacturer even bothered to include a VGA socket at all. Even if you can get a picture, then depending on your set, it may be noticeably poorer than what you can expect by using a HDMI input. Sure, you can use the XRGB3’s digital output, but that limits you to B0 mode (no scanlines) and actually has terrible compatibility with modern TV’s too.
To get around this problem, using a second scaler/adaptor behind the XRGB3 is a common practice. The DVDO Edge is one such solution, but it can be expensive and may provide a lot of functionality you don’t need. If you need something smaller and more specialized, perhaps for a retro-gaming cabinet project, the Gefen VGA to DVI scaler plus (hereafter referred to simply as the Gefen) is an ideal fit.
What is the Gefen VGA to DVI Scaler Plus?
The VGA to DVI Scaler Plus is a small (5.8” W x 1” H x 4.1” D) device that takes in a VGA signal at one end and outputs a DVI signal at the other. The VGA signal can be up-scaled to a range of resolutions between 640×480 to 1080p. 15Khz (e.g SCART) video is not supported, but the device works just fine with the XRGB family of line-doublers.
How much does it cost?
Buying the device directly from Gefen will currently set you back a cool $329. However, if you are willing to wait, second hand ones come up on E-bay quite frequently. If you’re very lucky, you can obtain one for around £60/$100.
Does it add input lag?
Yes, 30 milliseconds of input lag/display lag is added, this is in addition to the input lag on your television already.
Using the Gefen and XRGB3 in tandem
The Gefen makes a great XRGB3 compatibility fixer. To get the best results:-
- Flash the XRGB3 to the latest firmware.
- Connect your consoles to the XRGB3.
- Connect the XRGB3 output to the Gefen via a VGA to VGA cable and connect the Gefen to your display with a DVI to DVI or HDMI cable.
- Enable gamer-mode on your display, if applicable.
- Turn on the XRGB3, make sure one input (console) is powered on and selected then enable B1 mode.
- Change the XRGB3 output resolution to 640×480.
- Change the Gefen’s output resolution to 1080p, or closest to your panels native resolution.
- Set the Gefen’s scaling to Panscan Full, H-position: 0, Clock: 99, Phase: 0.
Known problems
The Gefen has pretty much the same compatibility as the DVDO Edge, meaning that the following systems still cause problems when using the XRGB3 and the Gefen together:-
- Neo Geo MVS
- PC Engine/Supergrafx all models (
though it depends on your RGB modno known mod is compatible) - Sega Megadrive/Genesis (see the note below)
- Sega Megadrive/Genesis when using the Sega Master System converter (unable to stop picture flashing on or off, currently no known fix)
- Sega Saturn (see the note below)
If you use a Sega Saturn or a Sega Megadrive with the XRGB3 in tandem with the Gefen, you will experience a loss of picture when the screen goes bright. This can make some games (e.g Sexy Parodius, during the thunderstorm in level 3) completely unplayable. To fix this problem, you need to use the consoles composite sync output instead of composite video for sync. This is pin 1 on the NTSC Saturn’s AV output but unfortunately does not exist on a PAL Saturn without performing a hardware modification. See this page for more information about composite sync.
The screen blanking issue is well documented on the XRGB3 wiki and affects other displays/processors and games consoles too.
No V-sync lock / Output frame lock control
A significant oversight I made when I originally wrote this article was not mentioning that the Gefen doesn’t have a V-sync lock option. This means that there is almost always a frame-rate conversion going on when you feed in the signal from the XRGB3. The result of this is that scrolling is not 100% smooth. Some people are more susceptible to noticing this than others. It would appear after further research that the Gefen /does/ v-sync lock. However, you cannot override this, so for instance if you need to do a frame-rate conversion (for instance on a console with a vertical sync too far out of spec) you do not have that option.
Screen tearing/stuttering with certain displays (possibly related to the above)
When using the Gefen and XRGB3 in tandem, the image will exhibit tearing or stuttering on some displays. There is currently no known workaround for this other than to power cycle the unit. See this thread on the Gefen forum for more information. Looks like Gefen have deleted the thread on their forums discussing this, make of that what you will.
Finally, here are some bad digital camera pictures of the Gefen up-scaling the XRGB3’s picture, of course the moire patterns are not present when looking at the actual screen:-
If I already have an xrgb 3/gefen combo, is it even worth it to seek out a dvdo edge?
The DVDO Edge has significantly less input lag and better zoom/pan controls.
This is different from a simple vga to dvi/hdmi converter I assume. If you trusted your TV to upscale 480p, then you would simply use a converter correct?
Where the XRGB3 is concerned there are no guarantees it will work.
Actually, not the Optoma, I just tested one and couldn’t get the Genesis/MD and XRGB3 combo to work with it at all.
Ah right yes I know exactly what you are talking about now. No, it doesn’t correct for that since it doesn’t have picture zoom. Your TV is unlikely to correct for it either unless that has a picture zoom feature. You’d need something like a DVDO Edge or an Optoma Themescene to do this.
Well specifically on the Megadrive/Genesis you tend to get colored borders around the game area (such as in Sonic 2), and you also get a lot of just graphical gibberish at the bottom left corner (only in certain games). Things like colored dots.
This is all part of the genesis video signal, and you can even see it on an emulator if you disable the overscan correction. When feeding my XRGB directly into my TVs VGA port it doesn’t do any sort of overscan correction at all, I guess I was hoping that the Gefen could compensate. There is still the chance that if I feed it via HDMI that the TV can do enough overscan correction by itself.
When using a genesis/megadrive via composite sync through the XRGB->Gefen chain, can the gefen ‘fix’ the overscan issues? I noticed in the documentation on the site it has multiple settings for dealing with overscan and I was curious if you had any first hand experience with this.
The Gefen doesn’t have picture zooming controls like the Edge does, what overscan issues do you mean exactly?