For anyone interested and with 30 minutes to spare, I would recommend the youtube video [1] by Reducible for an intuition on how FFT works.
If anyone is interested, I made a video about my favorite application of the 2D discrete Fourier transform, where it's used to erase rainbows on manga screen tones on color eink Kaleido 3 on Kobo Colour: https://youtu.be/Dw2HTJCGMhw?si=hlhwHv0qB6SoMha9
Who uses square brackets for big-O?
A bit of a stretch, but does anyone have a good way of running an FFT on a pcap?
You mean like converting packet timestamps into a (uniformly) sampled time series (e.g., bytes or packets per ms) and run a NumPy/SciPy FFT on that series?
Something like Lomb–Scargle would possibly be a better fit I suppose. But yes that sort of flow, I could do it as a one off with a Python script as you state, but my interest is more if anyone has sunk their teeth into network packet analysis in the frequency domain from the ground up and wrapped up all the learnings into a thoughtfully designed interface.
I was searching for a Wireshark type plugin to do this but I couldn’t find anything.
Alternatively, equally useful would be learning about anyone who has started to do something like this and then realized that it didn’t actually help them analyze anything.