Something that might be obvious to some people here, but wasn't obvious to me --
If you're trying to sample an LFO signal and use this to control video, make sure that the sample rate is an exact multiple of the control block size. This is not the case for 44.1 kHz vs a 64-sample control block (but it is the case for 48 kHz vs 64 samples).
In this patch, it looked like the logic was correct, but the LFO "jumps" about once per second.
But if I start JACK with a 48 kHz sample rate, then the same patch is perfectly smooth.
Curiously, though, setting the block size to the largest power-of-two factor of 44.1 kHz ([block~ 4 1 1]) doesn't affect the behavior at all. (Fun fact: 44100 = 2*2 * 3*3 * 5*5 * 7*7.)
Probably this affects any similar use of [tabwrite~] but the impact is more dramatic when it's controlling graphics.
Something to be aware of...