4K XAVC Playback Performance issue on latest top spec MacBook Pro (2017)

Hi all,

Wondering if anyone else has experienced this issue or has any advice.

Have just migrated from a mid 2014 15" MacBook Pro (top build to order spec) to a latest gen 2017 MacBook Pro Touch Bar (top build to order spec).

I have noticed that on the new laptop playback of 4K XAVC files from FS7s etc in Better Quality mode appears to be jittery or looks like its dropping frames (despite fcpx not warning that this is whats happening). The same files play perfectly smoothly on the mid 2014 machine. I have also noticed that the files play perfectly smoothly in Davinci on the new machine so it appears to just be an FCPX problem. There is also some jerkiness (though not as bad as FCPX) in Quicktime player I have tried all the usual problem solving steps including a complete clean system reinstall but the issue is still there.

Does anyone know what the problem here is or have you experienced something similar?

Thanks in advance!
Matt

Compatible camera page says 2K and 4K media from this camera should be optimized.

Yeah I know that's the official line but the fact is I don't have to in FCPX on a 2014 MBP. Or for that matter in Davinci on a 2017 MBP. The files even seem to play fine in QuickTime but FCPX on the 2017 MBP can't handle it for some reason.

Matthew Dove wrote: ...new laptop playback of 4K XAVC files from FS7s etc in Better Quality mode appears to be jittery or looks like its dropping frames (despite fcpx not warning that this is whats happening). The same files play perfectly smoothly on the mid 2014 machine. I have also noticed that the files play perfectly smoothly in Davinci on the new machine so it appears to just be an FCPX problem. There is also some jerkiness (though not as bad as FCPX) in Quicktime player...

By "playing" I assume you mean scrubbing the timeline or skimming clips in the Event Browser at various speeds?

XAVC from an FS7 can be XAVC-I (intraframe) or XAVC-L (long GOP interframe). In general smoothly scrubbing any type of 4k H264 long GOP codec is extremely difficult. Almost any editing software on almost any machine will require proxies or optimized media for this. Even a 12-core Mac Pro D700 is not fast enough. The only exception I've seen is my top-spec 2017 iMac 27 is just barely fast enough to edit a single stream of 4K long GOP H264 without transcoding to proxy. This is may be due to the improve Quick Sync logic in the Kaby Lake CPU.

The brief XAVC-L test clip I have plays smoothly in QT on a 2016 top-spec MBP and 2017 top-spec iMac 27. It also does OK within FCPX, but maybe it's too short to be representative. As stated above, *any* long GOP 4k format is potentially sluggish on almost any hardware.

All long GOP formats are not the same -- there are encoding difference in each one regarding GOP size, whether each GOP is truly independent or has cross-GOP references, distance between I or P anchor frames, etc.

Based on some testing I did six months ago on a 2015 top-spec iMac 27 it appears XAVC-L is not as smooth on FCPX as (say) 4k H264 material from a Panasonic DVX200. But in general you should plan on transcoding to proxy any 4k long GOP H264 format.

I mean play back as in selecting a clip in the library and hitting space bar playing. All XAVC-I no long GOP in sight.

All XAVC-I no long GOP clips involved in this instance. Jittery just playing through at normal speed with space bar. Working with apple engineer on it at the moment. Will update if we figure it out!

After much testing it appears the issue is with the discreet Radeon Graphics card or how core video / QuickTime talks to it.

If I try to play through a 4K XAVC or Proress 422 file in FCPX it appears somewhat jerky like it's missing occasional frames. If I export a 4K prores, close FCPX (so the mac switches to integrated Intel graphics) and play in QuickTime, it plays as smooth as butter. If I turn off 'auto graphics switching' thus forcing QT to use the Radeon graphics card instead then the same file plays back slightly jerkily just like in FCPX.

It's been escalated to Apples Engineers but in the meantime if anyone else has the same set up as me (latest top spec MBP 15", latest FCPX, latest Mac OS) then it would be great to know if you've experienced these problems? Just so I can start to narrow it down to being just my mac or a bigger problem / bug with this set up in general.