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No realtime playback to broadcast monitor: where's the bottleneck?

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Alan Okey
No realtime playback to broadcast monitor: where's the bottleneck?
on Feb 22, 2017 at 5:57:41 pm

I recently installed a Blackmagic DeckLink Mini Monitor into my system at work. It's a 2010 Mac Pro 5,1 with dual 2.4GHz 6-core Xeons, 12GB RAM and an ATI Radeon HD 5770 GPU. It's an older system, admittedly, but I'm perplexed by the inability of the system to play back anything in Resolve in realtime when broadcast monitoring is enabled.

I'm fully aware of all of the optimizations that can be enabled/used when working in Resolve to improve playback and editing performance. What surprises me is that when simply opening a clip in the source monitor (1920x1080 29.97 ProRs 422, for example), Resolve can't play back the clip in realtime when the broadcast monitor output is enabled. When it's turned off, no problem - I get full frame rate realtime playback in the GUI. However, as soon as I switch on broadcast output, playback slows to between 7-15fps. Keep in mind that this isn't even playing back video from within a sequence, with gases applied, etc. - it's simply opening a source clip in the source monitor and playing it back.

I have no playback issues in Premiere Pro, Autodesk Smoke or FCP 7 on the same system.

Is this typical behavior for Resolve, or should I be troubleshooting something specific? Where is the bottleneck here?


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David Roth Weiss
Re: No realtime playback to broadcast monitor: where's the bottleneck?
on Feb 22, 2017 at 6:25:38 pm

It's not typical on my 8-core MP 3.1, however I do have an nvidia card running under Cuda.

David Roth Weiss
Director/Editor/Colorist & Workflow Consultant
David Weiss Productions
Los Angeles


David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.


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David Roth Weiss
Re: No realtime playback to broadcast monitor: where's the bottleneck?
on Feb 22, 2017 at 6:29:54 pm

Are you certain the monitor is capable of displaying your chosen frame rate? If the material is 24p you may have to chose 60i playback through the BM card, if the monitor can't natively display 24p.

David Roth Weiss
Director/Editor/Colorist & Workflow Consultant
David Weiss Productions
Los Angeles


David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.


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Alan Okey
Re: No realtime playback to broadcast monitor: where's the bottleneck?
on Feb 22, 2017 at 6:34:11 pm

The footage and the broadcast output settings are the same - 1080i 59.94. The card is properly configured in the Blackmagic Desktop Video Setup utility.

Again, the Mini Monitor card performs perfectly in other applications. It's only within Resolve that I am unable to achieve realtime playback.


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Tero Ahlfors
Re: No realtime playback to broadcast monitor: where's the bottleneck?
on Feb 22, 2017 at 7:11:12 pm

Do you have another GPU you can test? That one is ancient and doesn't have enough VRAM for Resolve (if it is the 512 MB one).


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Alan Okey
Re: No realtime playback to broadcast monitor: where's the bottleneck?
on Feb 22, 2017 at 7:43:00 pm

[Tero Ahlfors] "Do you have another GPU you can test? That one is ancient and doesn't have enough VRAM for Resolve (if it is the 512 MB one)."

The 5770 has 1GB VRAM. I don't have a better GPU that I can swap for testing purposes, so I guess I'll just have to live with it. It's not a big deal for grading, but for anything that requires realtime playback, I'll just have to switch off the broadcast output or use a different app.


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