I have the Atlona AT-HD500 vga to hdmi scaler that I use exclusively for DC. It costs as much if not more than a Framemeister and has far less functionality. However, it is studio quality and if their is any lag it is undetectable by our eyes.
Alot of people that capture Dreamcast video use a cheaper vga to component converter. That way your converting analog to analog with no upscaling, thus skipping the extra analog to digital conversion process (vga to hdmi) with no lag. You'll need to get a cheaper capture card that has component inputs if yours doesn't already. Luckily they dont cost that much but it is the best way to capture DC footage with no lag