Hello Q_Ball,
You cannot convert composit/s-video (an analog signal) to digital format on the fly through any cable that I know of.
The same thing applies to VHS tape conversion: analog signal that needs to be converted to a digital format before it can be used in the digital world, such as DVD recording.
So, check out this site for information:
http://www.datavideo.us/products/dac100_mainpage.htm
I use the DAC-100 for converting old VHS (and other sources) into digital format so they can be used in DVD productions.
If this is not what you want to do, let me know. And by all means, post back what you end up doing so all of us can share the wisdom.
Respectfully,
Bill Gallagher