stimmer:
The more I think about this the more I wonder if it might actually be possible - an R-2R ladder on the external memory pins (34-41) together with DMA should work reliably at 10.5MSPS and may even go as high as 21 or 28MSPS (I learned that doing the VGA library). The dealbreaker would be how close to the exact colour subcarrier frequency you have to get. In my experience, with old CRT TVs you have to be very accurate, but more recent LCD panels have more tolerance for the frequency and amplitude of the colour subcarrier being wrong.
That would be awesome, but first I need to add an op-amp to my ladder, otherwise the signal drops when connecting to my camera. Can you give me some lm#### ic numbers?
Edit: I ordered some samples of the AD811 (AD811 Datasheet and Product Info | Analog Devices). It seems to be a good one. I hope I will get them in a week or 2.