I don't know a lot about LT spice,but I do know a considerable amount about video signals,& I think you may be in for a disappointment in trying to capture a video signal with a DSO to do anything other than those things a 'scope is intended to do.
I think you would be better trying to either create the video signal internally to your PC,or use simple waveforms to check individual characteristics of your device,
For instance,you can check the steady state response of the circuit with a swept frequency signal,& the rise time with a simple square wave pulse,or you can probably simulate a 2T pulse for the same purpose.
A 50Hz (or 60Hz) square wave signal will check your LF response.
It is only when you get into timing critical tests,or those which require a "real" video waveform that you will be in trouble.
Clamp circuits,& anything to do with manipulating the video information fall into both of these categories.