S-Video/Firewire ADC/DAC Virtual Reality

I’m getting a VR-4 with sync-on-green/external sync HD-15 inputs and s-video inputs. For stereoscopic video, I’ll need two sources in ntsc. Is there any device out there that is a hub with at least 4 s-video jacks programmable through a firewire 400 interface? I dont mind writing c/++, but I’d like to use the isochronous channels to acquire and route the video (especially for adding digital effects, I’ve already started looking at uncompressed lossless codecs). Or any other configuration that comes to mind.