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random bars appear across top or bottom of frame in Resolve 12 project

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Mathew Farrell
random bars appear across top or bottom of frame in Resolve 12 project
on Dec 20, 2016 at 6:20:33 am

Hey folks.

I've just been cutting a stop-motion project in resolve 12 (lite). Every so often, there is a narrow bar superimposed across the image, top or bottom of frame. Sometimes it is pure noise, sometimes is seems like a crop from elsewhere on the screen.

The bars appear at random places along the timeline, popping up successively during an edit session. ie there are none at the start of a session, and like a cancer, a few have appeared by the end. They appear in the rendered output.
If I restart Resolve, the bars are gone, possibly to return in new places.

The footage I'm using is a series of JPGs generated by a stills camera, roughly 4k dimensions, sRGB. I started this project using DNG stills, but replaced them with the JPGs because I liked Adobe's conversion better than resolves. To be clear, the JPG version is actually a fresh project file, but the issue appeared in both project files (DNG and JPG versions).

My system is a 2014 27" imac with decent spec (though the base level GPU).

Anyone know what on earth I'm talking about, or even better, how it might be avoided?

The attached image a screen grab of one of the bars.


Mathew Farrell
flowstate.com.au


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Joseph Owens
Re: random bars appear across top or bottom of frame in Resolve 12 project
on Dec 20, 2016 at 4:53:28 pm

Seems like a GPU failure, or it is a CPU decoding deficiency. The iMac is not particularly well suited to above-HD resolutions, and you have loaded it down with a fairly heavy media extraction task. While most grade software has evolved from .cin and .dpx sequential image formats, the original hardware platforms were Linux/Unix servers. Commodity-level PCs seem to deal more readily with .mov formats, with the best compromise centering around intra- flow codecs like ProRes and DnX -- and this seems to be a defining difference between producing motion media as an animation/photographic methodology vs. a cinematographic one.

jPo, CSI

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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Mathew Farrell
Re: random bars appear across top or bottom of frame in Resolve 12 project
on Jan 19, 2017 at 11:01:19 pm

Cheers Joe, I only just saw your reply.

Mercifully I got the project out the door cleanly. I'll do a bit more experimenting to see if I can break it again and try and predict the behaviour.

Such a shame the imac is a locked box w.r.t. video card. It would be great if we could loop out to a better card.

Mathew Farrell
flowstate.com.au


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Bill Ravens
Re: random bars appear across top or bottom of frame in Resolve 12 project
on Jan 20, 2017 at 3:11:06 am

I'm seeing the same thing. It seems to happen with only certain types of transcodes. As I recall, conversions to MXF/ OP1A DNxHR. The problems seem to have started with Resolve v12.5, as I never saw this before that version, with the same kinds of outputs. BTW, I'm on a PC not a MAC.



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