This really hits if you try to merge audio which has been recorded separately from video (e.g. Raspberry Pi where at least a few years ago software did not supp

This really hits if you try to merge audio which has been recorded separately from video (e.g. Raspberry Pi where at least a few years ago software did not support recording audio synchronously with video). And the worst thing is- it could vary from one device to other because the crystal oscillators used for image sensor clock have slightly different resonant frequency (which is caused by manufacturing tolerances when cutting the crystals).