Latest post Thu, Apr 30 2020 11:33 PM by Jan Klier. 3 replies.
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  • Tue, Apr 28 2020 7:09 PM

    • Jan Klier
    • Not Ranked
    • Joined on Sat, Oct 12 2019
    • New York City
    • Posts 4
    • Points 60

    EXR Roundtrip - Color Space

    Now that MC can both write and read EXR files, which is quite welcome, one issue I've run into is color space handling.

    I just had to send one clip for object removal. Standard HD sequence in Rec709 - a mixdown of the main timeline, so no color or effects. Selected the clip, exported EXR sequence. Opening the sequence in the VFX software, the blacks are crushed. Doing a straight render in VFX (without changes) and re-linking into MC brings the same crushed blacks into MC. The round-trip should be seamless if no changes are made anywhere. But it doesn appear to be.

    I checked and couldn't see any settings in EXR output. 

    If I do the same from other software (e.g. Resolve) I don't run into this issue.

    For now I wored around this by rendering DNxHR 444 out of MC for that clip, taking that into resolve for transcoding into EXR. Then after VFX EXR render, bring the results into Resolve to transcode EXR back to DNxHR444 and then back to MC. That ended up seamless, but is two extra steps. 

    There must be something I'm overlooking in how MC handles EXR exports??? Is there a need for specific clip source settings? Maybe full vs. video levels?

    Also I noticed that occassional EXR linking has hiccups. Occassionsly in the source browser after media processing one or more frames have 'cannot process' in the status and then they're missing.

    PS: Ran into the same problem a few weeks ago on 2019.12. Now on 2020.4 with same issue.

    MC 2019.9, Win10, Intel i9-9960, 128GB, RTX 2080TI, AJA IO4K+ [view my complete system specs]
  • Thu, Apr 30 2020 10:57 AM In reply to

    • Joachim Claus
    • Top 150 Contributor
    • Joined on Fri, Nov 4 2005
    • Seeheim-Jugenheim, Germany
    • Posts 948
    • Points 12,125

    Re: EXR Roundtrip - Color Space

    Jan Klier:
    There must be something I'm overlooking in how MC handles EXR exports??? Is there a need for specific clip source settings? Maybe full vs. video levels?

    Hi Jan,

    thre is an export setting for EXR, where you can select between EGB and YCbCr color space. I do not know whether this implies a different color value association. Give it  a trial with both settings and see what th result is.

    Joachim

     

    P.S.

    I tested export a 5s color bars chart video with RGB color model and YCbCr color model. Resolve cannot read the YCbCr exported file, while RGB exported file is ok. However colors are converted to full range, i.e. video levels of the color bars are transformed to full RGB-range. 

    Joachim

    SuperMicro Workstation 7048A-T Dual Xeon (10 cores) E5-2640v4 2.4GHz 128 GB RAM, PNY P4000, 1 PCIe SSD 400 GB (Intel SSDPEDMW400G4) 1 SSD 2 TB for UHD... [view my complete system specs]

    Joachim Claus

  • Thu, Apr 30 2020 11:33 PM In reply to

    • Jan Klier
    • Not Ranked
    • Joined on Sat, Oct 12 2019
    • New York City
    • Posts 4
    • Points 60

    Re: EXR Roundtrip - Color Space

    Joachim Claus:
    I tested export a 5s color bars chart video with RGB color model and YCbCr color model. Resolve cannot read the YCbCr exported file, while RGB exported file is ok. However colors are converted to full range, i.e. video levels of the color bars are transformed to full RGB-range. 

    Thanks for checking it out.

    I've had similar findings. When exporting with YCbCr the file cannot be opened anywhere outside of Avid. Resolve, Photoshop, and SilhouetteFX all show errors or black frames. RGB works fine.

    Upon re-importing the sequence (even without rendering or touching in any other software), by default it comes in too dark. Looking at the source settings, the source color space defaults to Linear/Rec 709.

    To get the clip to look identical to the source, you have to first add a 'Levels Scaling (full to legal)' and then a 'Linear to Rec709/2020' transformation. With both of those in place the roundtrip is seamless.

    However, in loading those EXR files into SilhouetteFX which has view transforms, if I add the linear to Rec709 transoform I have the same issue that they're too dark.

    So I think the legal to full data level change Avid appears to be applying during the export maybe should not happen from a VFX pipeline view. It distorts the data.

    But at least in the meantime we can work around it.

    MC 2019.9, Win10, Intel i9-9960, 128GB, RTX 2080TI, AJA IO4K+ [view my complete system specs]
  • Fri, May 1 2020 12:46 AM In reply to

    • Ben F
    • Not Ranked
    • Joined on Thu, Oct 13 2005
    • Los Angeles, CA USA
    • Posts 8
    • Points 90

    Re: EXR Roundtrip - Color Space

    I am running MC 2019.12 and successfully swapping EXR 16bit Uncompressed in Aces with no shift between Resolve 16 and Avid.

     

     

    HP Z840, Media Composer 2019.12 [view my complete system specs]
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