Dreamcast

The Sega Dreamcast is a video game console released in November 1998 in Japan and in late 1999 in other territories. The machine was Sega's last home console, it enjoyed modest commercial success and has a large library of games. When integrating a Dreamcast into your gaming setup, the most notable feature of the console is its unusual range of video output capabilities. Various Dreamcast titles can be output in 240p/15khz, 480i/15khz and/or 640x480p VGA/31khz. Not all titles support all screen modes and to get the most out of your Dreamcast library you may need to either cable swap or build a modified VGA box.

Universal RGB VGA Box

To play games in VGA on the Dreamcast, it is necessary to buy a VGA box or VGA cable specially designed for the console. When using this accessory, normally 15khz RGB is locked out, probably to prevent consumer confusion as very few display devices support 15khz RGB via a D-Sub 15 (VGA) connector. In the case of the XRGB3 and the XRGB Mini too, it is possible to use both 15khz and 31khz through the same cable. By means of a simple hardware modification, most VGA boxes for the Dreamcast can be modified to output both 15khz and 31khz. For more information, see this link.

XRGB-3 Specific settings

With the universal VGA box modification, you can connect the Dreamcast directly to the D in 2 port on the back of the XRGB3. The XRGB3 will then process all incoming signals, allowing you to play all games in RGB with no cable swapping.

XRGB-Mini Specific settings

The Mini's RGB in socket will accept a 31khz signal, but it must be a RGBC signal and not the more common RGBHV that VGA usually uses. It is possible to connect the Dreamcast's VGA output to the XRGB Mini via a sync combiner. If you have the universal VGA box modification too, that means you can play both 15khz and 31khz RGB games, just as with the XRGB3. You could use the ArcadeForge UMSA for instance, or modify a VGA box of your own with a sync combiner.

Below is a screenshot of Guilty Gear X on Dreamcast, running with the following settings:-

Smart x2 mode H_SCALER = 7 V_SCALER = 6 SHARPNESS = 1

Sharpness 1 and H_SCALER 7 may be too much. Using H_SCALER 6 or turning off the Sharpness function may produce better results.

The above settings only work properly in Smart x2 mode. Once you chose another image mode, V_SCALER = 6 is messy, as it does just nearest neighbor scaling and this results in jagged edges and pixel rows of different hight. V_SCALER = 5 is a proper scaling mode. It's a tiny bit softer than the scaling done by the Gefen VGA to DVI scaler, but still nice. Pay attention to the diagonal edges of the ice block in the picture below. V_SCALER = 5 on the left and 6 on the right.

Thanks to Fudoh for these recommendations/observations.