Does a RCA to SDI cable/adapter exist?

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http://serverfault.com – I'm currently outputting video from my Panasonic HDC-TM900k using the RCA out, and connecting it to my computer using a Easycap DC60+. I'm using this camera for live streaming over the web. The camera only has an RCA output, but I'd like a more elegant solution for connecting it to my computer, such as with a Blackmagic DeckLink SDI. Are there cables/adapters for RCA video to SDI, so that I can use this type of connection? Or is this just a silly thing to do? I realize that it won't "upconvert", that it will still be a RCA quality, but it will be connected to my computer in a better way. (HowTos)