Blackmagic Forum

i7 iMac 2.93gHz 24gb ram, High Sierra...latest free version 15 beta
3840x2160 .mov footage from a drone or iphone, will not play back smoothly. It's impossible to edit. 1920x1080 project works fine. Something is causing a proc overload. Nothing else running. Any ideas?

H.264 long GOP?

Footage is.mov from my iPhone and or DJI drone.

Constant frame rate or Variable frame rate? Resolve does not work happily with Variable frame rate.

No varicam...all constant fps

unless things have changed, iphones shoot in Variable frame rate. When you set a FPS to shoot in, it's only an approx target. the actual FPS is still variable.

You also don't mention the GPU in your computer. Compressed 4k takes a lot of compute power, and a really good GPU is needed.

It's a quad core CPU, ATI Radeon HD 5750 graphics with 1 GB of dedicated GDDR5 memory. I see people having smooth operation with 4K on iMacs.

Some of the UHD 4K footage came from a dji drone.

I guess the question is, does anyone else have a Mac, and are successful editing 4K with resolve?

1GB vram is way under spec for Resolve, let alone 4k. That and Variable frame rate will kill 4k playback.

You may get away with limited nodes and effects in HDTV, but 4K? No way!

I edited 4K in ProRes happily on an iMac with 16 GB RAM and 4 GB VRAM.

Now I'm on a 2017 iMac with the Radeon Pro 580 8192 MB and 32 GB RAM (mainly for Fusion). But even this machine stutters sometimes with temporal codecs like H.264 or, more so, H.265.

I second the trouble with smartphone 'video', it's often off-spec and most professional NLEs don't like that.
Even iMovie might be better at handling it.

Thanks All...so, if I can create ProRes out of my h264, do you think I may get things working to some acceptable level? Yeah, I’ve limited vram, but I’m hoping it might fly. I’ll see about down converting to 2k and try it.

I'd still think 1GB VRAM will not be enough.

But try transcoding to Prores, or DNxHD - it will help to some degree.

You can also set the timeline to 1080 for working on, then change to 4k for rendering.

Jeff Brass wrote:
You can also set the timeline to 1080 for working on, then change to 4k for rendering.

I’d be fine with setting the timeline to HD. Is that the setting for the project?

Yep

Interestingly enough, my iMac at work, 3.4ghz and 1MB of VRAM, works with an HD timeline (1080), and 4K clips. There's a little hesitation at the beginning of playback, but, once it gets going, it's fine. One of the variables, that I think might be causing issues on the home iMac, is that I've booted from an external firewire drive, running Sierra off it. I don't know if that has anything to do with the sluggish playback response in DR, but I'm gonna test that here at work, and boot off the same ext drive.
Update: I'm booted off the firewire drive now and the 4K project is working fine within a 1080 timeline. There's not a huge difference between this iMac and my other one. I'll have to make sure it was running off a 1080 timeline, but it appears this works acceptably. If my other iMac was using a 1080 timeline, then I'm gonna be at a loss. There's no more vram in this machine, and 2.93ghz, to 3.4 isn't a big enough difference to cause the choppy playback.