I like how if I plug both an HDMI cable and VGA cable into my laptop it'll just use both of them as additional screens.
Similarly the NES will output on both composite and RF at the same time and that's actually super helpful when recording a Zapper game because the RF connection can go right to your TV and not be affected by the lag of passing through and being processed by your recording device.
@rainwarrior I can choose between duplicating across them or using them as additional separate screens, and the VGA and HDMI screens can have separate stuff. If the main laptop screen worked I imagine I could have three separate screens?
We were recording NES footage with a rewritable DVD recorder so I think there was some sort of processing to be able to put a menu on top or other things. I don't remember the specifics.
@NovaSquirrel Hm, I've owned more than one laptop that could do 2 screens max (despite having 2 ports). I've also seen some that can only do 1 (and any connected monitors will be a duplicate screen).
I actually haven't ever seen 3 running directly from a laptop... (though I've seen USB3 video devices that can add screens beyond the built in ports), just was curious if yours can! That'd be kinda neat.
@NovaSquirrel Do you mean that your laptop supports 3 separate screens, or duplicates output to all of them?
BTW every passthrough device I've seen doesn't have lag, AFAIK, composite or HDMI doesn't matter. (I think lag would imply buffering, which would make the part unnecessarily complicated and expensive, all it needs to do is repeat the signal. Upscalers have lag for this reason.)