Uzebox SCART Interface
To use the Uzebox with SCART, you should connect R,G,B, SYNC,GND, AUDIO to scart connector, also solder Rgnd, Ggnd,Bgnd, AudioGnd and CompositeInGND together and to GND. Take RGB signals directly *before* 100nf capacitors.
VERY VERY VERY important: Connect 160 Ohms resistor to 5v and route this signal to pin 16 of SCART - that will switch scart to RGB mode.
That's all! No AD725 needed. I'm planning a daughterboard with AD725, but buying it here is a problem (I already mentioned it).
Regarding Samsung. Those guys have not routed RGB signals on SCART - that's the problem and it's quite common for this vendor =). Only composite and (may be s-video - chroma + luma)
Regarding all those timings. Even russian brands of TVs now support pal/secam/ntsc. It adapts to the signal automagically, and you can always switch manually to desired system. The pins on scart are the same for all. I had only one issue on Dreamcast, when TV could not detect signal type, but manual switch solved problem.
But do note that if you wire the Uzebox directly to a SCART CABLE, you want to wire the SYNC to pin 20. If you wire it to a SCART SOCKET (like I did), you want to wire it to pin 19! I've just checked and various sources say that all SCART cables have pins 19 and 20 inverted. The same is apparently true for audio and composite video.