Just a couple of things to report on for potential or existing XSELECT-D4 owners.
Firstly, it is now available from National Console Support
. The price is $199.
Secondly, in response to a query from NCSX, I spent some time playing with my PS2 and input #5 on the XSELECT-D4. That's a 21-pin RGB port, aka Japanese RGB. NCSX reported problems getting interlaced video to work with this port.
The configuration I used when investigating was as follows:
Console (DC or PS2) connected to XSELECT-D4 via Japanese RGB cable connected to input #5 configured for RGBCS. D-Terminal output connected to D-Terminal input of an XRGB-2+. VGA cables connected to a switch box.
Now, I didn't have any problems with interlaced video from both a Dreamcast and a PlayStation 2, but I did with progressive scan from the PS2. My sole progressive capable game, SOCOM: US Navy Seals, totally lost video (but not audio) when progressive scan mode was enabled. It hadn't had a problem when connected using a Sony D-Terminal cable.
At this point, the PS2 was configured to output RGB, and input #5 on the XSELECT-D4 was configured for RGBCS. A little fiddling revealed that by changing the PS2 so that it output Y-Pr-Pb, and the 21-pin RGB so that it accepted YUV and the switch from interlaced to progressive scan occurred without problems.
NCSX are doing some experimentation of their own and if they get back to me, I shall report further.