[High Speed Dubb]

It’s working well here — no crashes, and no artifacts.

I like the aspect that you give up averaging beyond a certain time if that timepoint shows evidence for motion. It would be interesting to see the same trick used for spatial smoothing, in which an intervening pixel of a different color would prevent averaging with a pixel further away.

The threshold of 2 is probably a little too low to make this effective. At that value, even very light noise is going to cut the averaging range short. At least for over the air stuff, you can expect a mean difference of about 4 to 7 (for luma and chroma combined) even in stationary areas. (Thanks go to folks over in the video capture forum for that number.)

If you decide to put more effort into this sequential approach, you might eventually want to look up hidden Markov models (HMMs). You could use an HMM to infer the probability that motion began at any particular time in the sequence.