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Stuttering videos on iMac i5 2.5GHz mid 2011 El Capitan

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akira54:
Thanks Hendrik. I am at work now but I will check the details for you tonight and let you know. Thanks for taking this up.

akira54:
Video 1.72Gb
1280x720
Constant framerate
MPEG4
Progressive scan
Framerate 25 FPS

MacMini
OSX 10.11.6 (El Capitan)
i5 2.5 Ghz 2 core
AMD Radeon HD 6630M 256 Mb
8Gb memory
CPU running at some 24% peaking at 30-33%. Makes no difference what video I run, TV recording or full resolution Bluray rip with all the audio bells and whistles.

It looks as if all videos have this problem. I checked some TV shows, bluray rips, dvd rips and they all did it. In all cases the rips are NAS based (LAN). I'll try it later tonight with a SSD attached to the Mini to rule out a LAN bandwidth problem because in my experience on other machines W7 has a faster LAN connection with the server than my Macs have.

akira54:
Finally got around to testing the LAN throughput and can state categorically that it has nothing to do with that either (I quadrupled the throughput by switching to AFP). So is it the video processor? The mac has 8Gb memory, surely that should be enough? Since it was suggested it wasn't very powerful I checked the processor and it turns out to score slightly higher than the i5s in the 2014 Mac Mini, so that cannot be it either, can it? Could it be a MC problem?

blgentry:
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.

akira54:
Brian thanks for the response. I have been wrecking my brain over this issue now for several months and have reached a few tentative conclusions and I would love some feedback from those who are in the know about such things. First the good news. It wasn't MC at least not directly, but this is also where things become complicated. here are the facts:

(1) MC never used to have this problem until recently.

(2) Our home theater has both a projector (Sony VPL-HW50ES) and a monitor installed. I only ever use the monitor if I want to listen to some music without being bothered by projector noise. However, when I did test it with videos that showed a lot of judder I discovered that on the monitor the judder was gone.

(3) I then realised that a few months ago I sold my relatively new Denon AV receiver (AVRX3000) and replaced it with my much older one (Denon AVR-4308) which has far superior sound quality. To rule out the receiver (which otherwise does not give me any grief with the BR player, Sat receiver and PS3) I bypassed it for video and plugged the HDMI cable from my Mac Mini (W7 Bootcamp) straight into the projector. The resulting picture was smooth as a baby's bottom.

Since the setup in 3 causes some problems with switching sources I would still like to resolve it, but have a hard time reaching any conclusions based on the facts. Since my other sources (BR player etc) do not cause the problems I am having with the Mac Mini could it be that the output HDMI video signal is not correctly processed by the receiver? If so, is there anything I can do? If that plays a part, why does everything look fine on the TV monitor?

Any ideas on how I might proceed with this (what to test) would be appreciated.

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