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Resolve rendering out black frames inside mxf

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steve voyk
Resolve rendering out black frames inside mxf
on Mar 15, 2013 at 3:38:13 pm

Hi guys,
Resolve 9.1.1 on MacPro 2012 Hex core/Quadro4000, Cubix with 2 x GTX690.

We're processing dailies from Alexa RAW (.ARI) files to MXF DnXHD36 files.

We're finding that intermittently, single black frames are going through the system and being recorded onto the MXF file. We see the black flash frame on the GUI monitor followed half a sec later on the broadcast monitor.

This has happened a number of times in recent days and each time when we go back and check, the .ARI file is fine and we simply have to re-do the MXF again.

The only thing I can think of, is that we did discover that house sync was accidently feeding 50i into the project (which was 24p)... but I can't work out how/why this would affect the transcode.

Has anyone else seen these black frame issues?


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Juan Salvo
Re: Resolve rendering out black frames inside mxf
on Mar 16, 2013 at 6:27:35 pm

Hmmm seems like you're banging into the GPU Ram issue, but you're not dealing with particularly high resolution stuff.

I wonder if perhaps the OS GPU address limitation is causing this. To explain:

  • Mac OS X is limited to being able to address 4 GPUs. The GUI card eats one of these, so effectively you max out at 3 processing cards.

  • The 690s are each effectively 2 addressable cards on the same device. So if you have 2 690s you actually have 4 GPUS!

  • This means you've got 1 more GPU than what you can address through the OS.


  • Perhaps this is what is causing your issue.

    My recommendation: Pull out one of the 690s and see if that doesn't clear up the issue.

    BTW, do you have any other cards in the Cubix box?

    Colorist | Online Editor | Post Super | VFX Artist | BD Author

    http://JuanSalvo.com


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    steve voyk
    Re: Resolve rendering out black frames inside mxf
    on Mar 17, 2013 at 10:54:51 am

    Thanks Juan...
    Actually I made a mistake in my post.. I have two 4GB GTX680 (not 690).

    The other cards inside the CUBIX are a 10GB card and a USB3/SATA card.
    The problem is very intermittent so quite hard to pin point.

    Cheers


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    Juan Salvo
    Re: Resolve rendering out black frames inside mxf
    on Mar 17, 2013 at 4:33:41 pm

    Are you pulling media through the 10GigE card? What ram do your 680s have? 2Gb or 4Gb? What resolution is your timeline set to?

    If 10gE is pulling media, I would put it in the computer and move the decklink card to the cubix. One other thing you can do to have more consistent renders is to slow down a the processing by setting a slower max frame rate in the render config.

    Like it said, it sounds like you're hitting the gpu ram issue, but would seem odd as given you're making DNxHD files, you should be working at HD resolution.

    Colorist | Online Editor | Post Super | VFX Artist | BD Author

    http://JuanSalvo.com


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    steve voyk
    Re: Resolve rendering out black frames inside mxf
    on Mar 18, 2013 at 1:19:21 am

    No, not pulling the media through 10GigE card. It's coming from an external RAID connected to MacPro, being processed to MXF then recorded back out on same array. There is no other activity going on when we do this in order to safeguard the process. The project is 1920x1080 24p (not 23.98). We are actually slowing the render speed down to 25fps (no 24 setting) so that we can QC the shots as well, hence we've covered most of the bases.

    When we do get a frame of black, it's easy to see as it flashes on the GUI monitor, followed 12 frames later on the broadcast output.


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    Paul Provost
    Re: Resolve rendering out black frames inside mxf
    on Mar 18, 2013 at 5:59:51 am

    What cuda driver & gpu driver do you show when ou look at cuda control panel in sys pref?
    What OS?
    I have 3 x 680 4gb in cubix

    http://www.4Kfinish.com | owner-colorist | Hollywood, CA
    http://www.facebook.com/4kFinish


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    steve voyk
    Re: Resolve rendering out black frames inside mxf
    on Mar 18, 2013 at 9:58:45 am

    CUDA diver 5.0.36
    GPU Driver 8.0.61


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    Paul Provost
    Re: Resolve rendering out black frames inside mxf
    on Mar 18, 2013 at 4:53:59 pm

    I'm on 10.8.2
    Davinci told me to update to 5.0.37 and 1.3.4.0 (304.00.05f02) which I have
    You need lates drivers for non Mac cards directly from nvidia site (there's yet another for 10.8.3 now)
    I was having a similar problem, but not sure if the new drivers have resolved it.
    Please contact resolve support directly and report so we have more input. May be 680 related...

    http://www.4Kfinish.com | owner-colorist | Hollywood, CA
    http://www.facebook.com/4kFinish


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    steve voyk
    Re: Resolve rendering out black frames inside mxf
    on Mar 25, 2013 at 2:27:06 pm

    Paul,
    I've found that our black frame issue was the result of using Arri Rec709 LUt as a track LUT.
    Switching to Output LUT has solved the issue.

    Cheers


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    Paul Provost
    Re: Resolve rendering out black frames inside mxf
    on Mar 25, 2013 at 3:02:31 pm

    Well that's more of a workaround than solving it. I had the same problem. With the Alexa lut in a node I would get the black frame flashes. When setting as an output lut instead, the black flashes went away. I have 3 gtx 680. Davinci support seemed to think this was a 680 bug and asked me for support files which I provided, but have not heard from them since. Please send them your experience as it seems they were right and it may be gtx 680 related.

    http://www.4Kfinish.com | owner-colorist | Hollywood, CA
    http://www.facebook.com/4kFinish


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    steve voyk
    Re: Resolve rendering out black frames inside mxf
    on Mar 26, 2013 at 1:15:30 am

    Yes, it's a workaround.. but right now it means I don't have editorial screaming at me with black frames in their images.

    I have been liasing with BM guys directly in Singapore so they're well aware of the issue and looking into it.


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