I would recommend going with a mid-grade capture card. While there are some homebrew solutions – such as using a video out from your graphics card or converting from DVI>VGA>S-Video, the most reliable solution would be a capture card. You could get along with something like the Blackmagic design Decklink ($295) a basic card with SDI Monitoring out, SDI In and Out and RS-232 deck control. From there you can go up through the numerous Blackmagic SD cards – ranging from $295 to $895, gaining XLR audio,composite, etc. S/PDIF as you go up. Don’t know anything about AJA cards.
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Ross Neugeboren
GetTheShot