Qmetro might drop frames (or audio) because it is a lower priority than metro runs to the CPU. When do you use one over the other? Use Metro when you need sample accurate timing and cannot drop frames. Most people would say you can’t detect slight frame drops in video because you’re usually running faster than the eye can detect anyway so use Qmetro with video. But use metro for example when banging audio at some rate synced to a clock.
Is this the correct way of thinking regarding metrotempo?
"If I have a PAL movie with 25 fps shall I then think that I shall put the metro to [metro 40] to output a bang every 40 ms. That would equal 25 bangs each second. (0.04s x 25 = 1 s), and if I have a video with 29,97 fps that would equal: 1/29,97= 0,033.