Got some pretty interesting results doing a quick Google search for firewire video mixer, including a review/info on a Videomaker article http://www.videomaker.com/article/9510/ but that baby’s expensive. There is also one by Videonics MXProDV Digital Video Mixer.
Maybe some others there also, see what luck that brings you. I still use an old workhorse Panasonic MX12 that accepts S-Video inputs/outputs, and I have taken the signal from my Canon XL one pair, via S-Video, into a hard drive recorder, cleaned up, then piped out via Firewire to my Mac system for finish.
