iMac Pro iMac Pro, HVEC h265, GoPro 4k60 stuttering - macOS Catalina

[DomP1234]

Hi,

I have an 3.2 Mhz, 8 Core iMac Pro 2017, 64mb, Vega 56 system, with internal and external SSD.

When attempting to playback GoPro footage, 4k60 it starts smooth, then stutters like mad.

This happens in Photos, QuickTime, and VLC (with h/w decoding turned on).

Curiously, in VLC, if I turn h/w decoding off, there is no stuttering and playback is totally smooth.

The hardware is surely capable of playing this seamlessly, but, apart from the VLC option, I cannot get satisfactory results. Ultimately, I want to edit it FCPX.

Regards,

DomP

 

[DomP1234]

Is it worth adding that the 4k60 files work perfectly on my 2019 MacBook Pro?

 

[HarshStuff]

Hi Dom,

Were you ever able to resolve the issue? I just updated my iMac Pro to Big Sur and noticed the same thing (I never tried in Catalina). Can also confirm that if I disable HW decoding, it runs just fine.

Unfortunately instead of starting from individual video playback and then moving to FCP, I started from FCP and was ripping my hair out trying to figure out why playback was a problem.

I can also confirm I am not seeing this issue on my 2019 MacBook Pro which is running Catalina (neither on VLC nor on FCP).

I will likely end up using my MacBook for the current project, however it would be nice to move my workflow to my iMac (which I'm sure was your ultimate goal too).

Cheers!
Harsh

 

[Chrisjmv]

I have the same issues with GoPro 60FPS content or some other HEVC stuff. Also iMac Pro.
What can this be?
Also Big Sur 11.1

 

[abekislevitz]

Just to add - also on iMac Pro 3Ghz 10-Core 64GB of ram and cannot smoothly playback 4K-60 HEVC GoPro Files in Quicktime or Premiere. Can also perfectly playback on my 2017 Macbook Pro.
I thought I was going crazy so I cleared my entire harddrive, downgraded from Big Sur to Mojave, and then upgraded to catalina. Weirdly- I tried one file while I was on Mojave and the problem was fixed. Installed catalina and I'm back again.

 

[Chrisjmv]

So it seems something OS related?

 

[abekislevitz]

So it seems something OS related?

Seems that way. I've been digging into this for the last 6 hours and I've come to the conclusion that Apple turned off HEVC hardware support on the iMac Pro between Mojave 10.14 and Catalina 10.15. I went as far as dual booting my computer with both operating systems and editing the same project in premiere. The catalina one can't even scrub through one 4K-60 clip while the mojave one plays through smoothly.

I don't know why more people aren't talking about this - I guess it's just super niche and not very obvious. I would love to raise this to the folks at Apple because I bought this machine for editing video specifically (I'm creative director at GoPro), and they've basically turned off the support for it. Why?

 

[Chrisjmv]

Yeah. You are absolutely right.
I can’t get it why they have done it.
I thought my iMac Pro was defect. Editing a lot of GoPro and other 4K HEVC stuff.
On BigSur I found out when screensaver starts it stutters like hell after.
The Radeon Vega 56 Pro seems in a low Power State when playing HEVC coded content.
After reboot it works. But sometimes it doesn’t.
On M1 MBP no problems with that