@mwichary The "analogtv" module in XScreenSaver almost does that; it's a circuit-level simulation of NTSC and its various faults, so it's at the "analog logic" layer rather than the "physics" layer.
https://github.com/Zygo/xscreensaver/blob/master/hacks/analogtv.c
You can see the effect in action on most of the images posted on the @dnalounge account.
@jwz @mwichary Thanks for pointing this out!
For others who happen across this thread, it's also listed as #XAnalogTV on #XScreenSaver's #screenshots page:
https://www.jwz.org/xscreensaver/screenshots
Which, in turn, links to a sample video on #YouTube:
XAnalogTV: From the XScreenSaver Collection, 2003.
YouTube
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