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Black bars on side when rendering C4K footage

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Duke Sweden
Black bars on side when rendering C4K footage
on Sep 25, 2017 at 2:16:28 am

When I render C4K footage as 4096x2160 out of Premiere Pro/Media Encoder, I get thin black bars on top and bottom, as I should, since C4K is wider than a typical HDTV. But when I render it out of Resolve, I get wider black bars on top and bottom, and bars on the sides. What am I doing wrong? 1080p renders fine but I don't want to render at 1080p.

Dell XPS 8920
Intel i7 core 7700 build
GeForce GTX 1050ti
32 Gigs of RAM
3 7200 RPM SATA Drives
Windows 10 64-bit
Premiere Pro CC 2017 v.11.0


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Tero Ahlfors
Re: Black bars on side when rendering C4K footage
on Sep 25, 2017 at 4:21:21 am

What is your source footage? What are your project settings? What are your export settings? Are you using the free or the paid version of Resolve?


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Duke Sweden
Re: Black bars on side when rendering C4K footage
on Sep 25, 2017 at 10:25:39 am

I already said what the source footage is. Read my comment (Ah! The worm turns!)

I have export settings as 4096x2160, the same as my source footage. I have to keep the timeline resolution at 1920x1080 because for some reason 4096 fills my GPU RAM.

And it's the Studio version.

Dell XPS 8920
Intel i7 core 7700 build
GeForce GTX 1050ti
32 Gigs of RAM
3 7200 RPM SATA Drives
Windows 10 64-bit
Premiere Pro CC 2017 v.11.0


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Tero Ahlfors
Re: Black bars on side when rendering C4K footage
on Sep 25, 2017 at 11:25:18 am

Your timeline aspect ratio is 1,77 and you're exporting it to a wider 1,89 aspect ratio so you'll get padding on the sides. Also If you want a full quality 4K render you'll need to set the timeline to what you want. If you're working with 4K footage in an HD timeline and then exporting in 4K you're actually scaling the already downscaled 4K footage up and losing quality.


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Duke Sweden
Re: Black bars on side when rendering C4K footage
on Sep 25, 2017 at 8:41:10 pm

You see my specs. It's not an ILM workstation but it's pretty beefy. Why won't Resolve let me set a C4K timeline? I've cleared my RAM cache, and only have one project open, but I get that error message when I try to render with the timeline set to C4K (4096x2160)

Dell XPS 8920
Intel i7 core 7700 build
GeForce GTX 1050ti
32 Gigs of RAM
3 7200 RPM SATA Drives
Windows 10 64-bit
Premiere Pro CC 2017 v.11.0


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Tero Ahlfors
Re: Black bars on side when rendering C4K footage
on Sep 26, 2017 at 3:52:56 am

It's not about the RAM. It's about the VRAM on the GPU. I don't know what kind of corrections you've made and how much VRAM you have but according to the Geforce page it should have at least 4 gigs. Unlike Premiere, Resolve uses GPU for pretty much everything when you start adding nodes and effects and whether it can fit in the VRAM depends on what kind of stuff you're doing. For example if you have a lot of temporal effects that read frames backwards and forwards (like noise reduction) it will need to read more frames into memory thus requiring more VRAM to make that work.

Here's a quote from the Davinci config guide:

"For processing UHD or 4K-DCI images we recommend 8GB or more of GPU memory. For some operations 4GB will be sufficient. 2GM is not recommended."

You wrote about noise reduction before so as a workaround you might want to try exporting whatever you have with the noise reduction off. Then bring it back in and make another pass with only the noise reduction.


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Duke Sweden
Re: Black bars on side when rendering C4K footage
on Sep 26, 2017 at 11:38:50 am

Ah, ok. Yeah I've got 4GB of VRAM. I was able to render a 2:20 clip on a C4K timeline yesterday with quite a few tweaks but no noise reduction. Thanks, Tero.

Dell XPS 8920
Intel i7 core 7700 build
GeForce GTX 1050ti
32 Gigs of RAM
3 7200 RPM SATA Drives
Windows 10 64-bit
Premiere Pro CC 2017 v.11.0


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Tero Ahlfors
Re: Black bars on side when rendering C4K footage
on Sep 26, 2017 at 11:56:01 am

You could try if using only the spatial noise reduction would do. It should only check the current frame instead of keeping a bunch of frames in memory.


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Duke Sweden
Re: Black bars on side when rendering C4K footage
on Sep 27, 2017 at 10:14:04 am

Got it. I didn't really need to add noise reduction, I was just experimenting with it. Do you know if Neat Video is a lighter approach? It plays a LOT smoother than in Premiere Pro. I mean, it actually plays in a smooth slow motion, whereas PPro freezes up when I apply it.

Dell XPS 8920
Intel i7 core 7700 build
GeForce GTX 1050ti
32 Gigs of RAM
3 7200 RPM SATA Drives
Windows 10 64-bit
Premiere Pro CC 2017 v.11.0


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Tero Ahlfors
Re: Black bars on side when rendering C4K footage
on Sep 27, 2017 at 11:11:01 am

Noise removal/adding is always pretty heavy because you are affecting pretty much every pixel at every frame and in the case of temporal noise you're reading multiple frames.


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Duke Sweden
Re: Black bars on side when rendering C4K footage
on Oct 11, 2017 at 12:36:52 pm

ok, I think I was writing about one particular "project" when I first started this thread, so now I'm a lot clearer on what the problem is. On all 4 of my "projects", the c4k footage on a c4k timeline fills the source monitor correctly, except for one project (the one I originally wrote about here). On this one project, although the specs are the same (C4K footage in a C4K timeline) I get the black bars on the side in all of the pages (media, edit, color and delivery).

Is this just an odd happenstance with no solution?

Dell XPS 8920
Intel i7 core 7700 build
GeForce GTX 1050ti
32 Gigs of RAM
3 7200 RPM SATA Drives
Windows 10 64-bit
Premiere Pro CC 2017 v.11.0


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Duke Sweden
Re: Black bars on side when rendering C4K footage
on Oct 11, 2017 at 12:39:51 pm

AHA! Found the problem. Posting it here for the benefit of others who are as dumb as I am. I was using proxy files that I had generated in Media Encoder, which have a different aspect ratio. At the time I didn't know that Resolve also had the ability to generate proxies so I imported already created proxy files generated when I was using Premiere Pro.

Dell XPS 8920
Intel i7 core 7700 build
GeForce GTX 1050ti
32 Gigs of RAM
3 7200 RPM SATA Drives
Windows 10 64-bit
Premiere Pro CC 2017 v.11.0


Return to posts index

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