I have an 2011 Macbook Pro with a 2.0 GHz quad core i7. A reasonable machine even though it's "old" now. For quite some time I've been watching lots of video with MC21 and MC22 for Mac.
Most of the time it's normal. But some fraction of the time, I see "juddering" that's very similar to the video that was posted. Stop, start, stop, start, all in rapid succession. In some cases, I think the source video might be the problem. In others I'm not so sure.
A month or so ago, I tried to do some concrete experiments with 24 fps video as this frame rate is known to have weird issues with 30 fps (and 60 fps) devices. Pretty much all modern LCD monitors are 60 fps so... I used a well known movie, The Fifth Element, and saw some of this juddering behavior. But I couldn't totally nail it down. So I just moved on with my life and kept watching videos with MC. It wasn't perfect but...
A few weeks ago, my MBP was repaired and when it returned it was running a fresh installation of the latest OSX, 11.12 Sierra.
I've just done some more testing with this machine and the same movie. I can't seem to induce the juddering at all. Well.. maybe just a teeny tiny bit here and there. But nothing like it was before. It's nearly perfect now.
A few things are different on this machine. I'm not sure which is the most important, but I have guesses. Here they are:
1. Previously my internal hard drive was about 85% full. This time I've kept it rather empty by moving large files to an external hard drive. It's less than 30% full now. Previously I've noticed MC seemingly behaving worse and worse the more full the internal (OS) hard drive became.
2. OSX 11.12 appears to have much better memory management than the previous OSX I was using, which was 10.9.5 (Mavericks). It seems to use less RAM overall and does on the fly memory compression.
3. My hardware was repaired, including a new motherboard.
I think 1 or 2 is probably the big factor. If I had to guess I'd probably say 1 is the biggest factor, but I'm really not sure. All I know is that my video juddering is substantially reduced now. Though I need to do more testing.
Brian.