Poor Playback Quality on iMac 27" Late 2015

Dear Forum Members,

I'm an amateur video and music maker and I've been using Avid Media Composer to produce short projects for a number of years. I was recently encouraged to try DaVinci Resolve so I downloaded the latest non-beta version from the BMD website - 16.2.8.005.

I have to say that I was absolutely amazed by the GUI of Resolve - modern and intuitive, and in many ways what I have been wanting for years! Unfortunately, although I am very encouraged to swap over to DR for upcoming projects, I seem to have hit a road block in terms of playback performance on my rather dated iMac (system specs in signature).

My simple requirement is to compile footage from a Mavic Air 2 drone, shot in HD 1080p 1920 x 1080 50fps H.264 format. I want to make some straight cuts, a dissolve or two and cuts to music. Then deliver at the same resolution.

However, I find that my short clips will not play smoothly, either in Media Pool or on the timeline - instead they suffer from a jarring stutter every few seconds, making it very unpleasant to work on them.

Since I only have an AMD Radeon R9 390 2GB GPU, I thought that it must be struggling to produce smooth playback with the processor-intensive H.264 files.

As a result, I have spent many hours running through FAQs and posts on this forum, plus the various DR PDF manuals in order to find a solution.

I have tried:
1. Generating Optimised Media (in formats as low as DNxHR LB and ProRes 422 Proxy)
2. Changing system preferences for GPU usage (metal, openCL, CUDA)
3. Using Proxy Mode
4. Changing Video Monitoring in Project Settings to a lower bit depth

Unfortunately, none of these changes has solved my problem, whereas Media Composer running on the same computer, with the same "transcoded" format as the "optimised media", runs this footage completely smoothly. So before I slope off back to Avid, I thought I would at least ask the question whether I have any other configuration options that I might try on this hardware setup?

To reduce this problem to its bare bones...if I copy a raw drone file of 1.26 GB and length 2m23s to Media Pool, then Generate Optimised Media using either DNxHR HQ or DNxHR SQ, then try to play the clip in Media Pool - the footage stutters, as shown in the QuickTime screen recording linked below.

As you will see from the Mac Activity Monitor GPU and CPU graphs that I have included, neither the GPU nor any of the Quad Cores on my i5 seem to be maxed out. Indeed, quite a lot of the load on the GPU was generated by running the QuickTime screen recording itself! Resolve was in fact only using a fraction of the GPU bandwidth shown.

So, in summary, I would really appreciate any advice that anyone can offer, if only to confirm for me that my iMac simply isn't up to the job.

Many thanks in advance,

Jon



https://www. dropbox.com/s/laiqex743gglh3p/Screen%20Recording%202021-02-21%20at%2020.34.22.mov?dl=0

Instead of optimised media, transcode your footage to ProRes 422 (HQ if you like) and try again.
A fast disk should help, your internal one might be quite fragmented.

Many thanks, Uli

I have a major "thinks bubble" over my head right now concerning the difference between "transcoding" and "generating optimised media" in DR. I thought that was what I was doing by generating optimised media! But that's clearly not the case, if I read your post correctly.

I'll give it a try in the Media Management function and see if that makes a difference.

Appreciate your time and advice.

J

An update...and sadly no progress!

Following the advice above, I transcoded the clip in question to ProRes 422 HQ in Media Manager.

This resulted in a ProRes encoded file of just over 6GB.

I then added the newly transcoded file back in to Media Pool.

Disappointingly, this file exhibits similar if slightly less pronounced jarring stutters when playing the clip from the Media Pool viewer or from the timeline in the Edit Tab.

I'm coming to the conclusion that my iMac isn't up to the task, but the mystery remains that I can play the same file in Media Composer on this same computer without any problems. Very disappointing, as I am very impressed with everything else about Resolve, and excited by the prospect of moving towards BMD control surfaces and cameras.

Any other ideas much appreciated, perhaps from anyone using the same hardware setup.

Thanks very much, J

Well, your Mac is at the lower edge of hardware for DR. The software can do much, but is heavy on resources. Even my iMac 2017 with a good GPU is struggling sometimes.
What you could try is going back to version 15 and using a timeline in 1280 by 720 during editing and grading. Then increase the timeline to HD before final render.

Sooo....uninstalled DR 16.2.8.005 using the BMD uninstaller in Applications.

Installed DR 15.3.1.003.

Created new project and loaded the clip in question in to Media Pool.

Transcoded the clip to DNxHR HQ 1280 x 720 HD 720P, loaded the transcode back in to Media Pool.

No dice, I'm afraid...still stuttering on playback.

Ditto using ProRes 422 HQ 1280 x 720.

Tried the same thing with some H264 media from a different source, this time a Canon M50...same results.

Appreciate the ideas, but I seem to be up against some kind of system limitation here! Anything else I might try? Otherwise I think this project may have to go on the back burner until I upgrade my hardware.

Just a thought: you could try playing back using proxy on the timeline to get the timing of your edits right then go to normal quality to get the colouring right, depending on your workflow, etc. That way you don't need to transcode, although rendering might still take a time. If it does, slow the rendering speed down. Good luck.

Thanks, Stewart

I had tried using Proxy settings for playback, but gave it another go today just to be sure.

I can certainly lower the resolution using this method, but I find that the stuttering playback still occurs using proxy at half or even quarter resolution.

Appreciate the idea and your time. So disappointing as I love the look and feel of Resolve compared to "clunky" old Media Composer . I have a feeling that I'll have to revisit this whole project when I upgrade my Apple hardware.

But definitely don’t upgrade to an Intel Mac any more.
Even the current MB Air M1 is faster than yours

Before you go changing hardware I would suggest you try faster drives, and try and borrow an external gpu with more muscle. Resolve works much harder than media composer because of the way it decodes the colour space into 32 bit, so it needs a bigger engine. You might be able to augment what you have to add the muscle.
I have a 2017 iMac, it’s fast with HD and just gets by with 4K
Is your 2015 Mac thunder bolt two or 3 (thunder 2 is a bit slow for an external gpu)
The new iMac will be out soon, you might be able to pickup an older model that suits at a reasonable cost

These are reasonable options, but if your Mac has only TB2, an eGPU would be pretty much wasted.

Thanks all for the ideas.

I was indeed considering an eGPU, but this iMac has TB2 ports and the findings elsewhere on the forum seem to suggest that only TB3 ports with a transfer rate of 40Gbps would give a significant improvement in performance with an eGPU.

Regarding faster drives, I am currently using the iMac's internal 1.0TB SSD. This is actually a brand new drive, fitted by a professional Apple repair house only two weeks ago, so I don't think that fragmentation should be an issue.

That said, I suppose the SATA internal drive might be some kind of bottleneck, and I was wondering whether a TB2 (20Gbps) external drive from the likes of LaCie or G-Technology might improve matters. Anyone have any experience of using such drives for video read/write for NLE on Apple hardware of this vintage (Late 2015)?

Thanks