Latest post Wed, Mar 6 2013 8:15 AM by MBrock321. 11 replies.
Page 1 of 1 (12 items)
Sort Posts: Previous Next
  • Sun, Sep 23 2012 7:13 AM

    • MBrock321
    • Not Ranked
    • Joined on Tue, Mar 1 2011
    • Posts 49
    • Points 605

    Same-as-source quicktime exports - ProRes and DnxHD differ

    <!-- /* Font Definitions */ @font-face {font-family:Cambria; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin-top:0cm; margin-right:0cm; margin-bottom:10.0pt; margin-left:0cm; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-fareast-font-family:Cambria; mso-hansi-font-family:Cambria; mso-bidi-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:72.0pt 90.0pt 72.0pt 90.0pt; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} -->

    I’ve been doing some tests of Same-As-source quicktime exports, comparing DNxHD vs ProRes footage.

    It appears that ProRes files exported Same-as-source from Avid behave differently than DNxHD exports in a couple of cases. 

    In a nutshell, ProRes exports always behave as though they were exported as RGB, regardless of whether RGB or 601 was chosen in the export dialogue. 

    My test procedure was to import the Belle-Nuit test chart as ProRes HQ and as DNxHD220x, with CCIR levels chosen on import.  These 2 clips became my basic test footage, and appeared identical in the Avid.  I exported the clips Same-As-source with both RGB and 601 levels, then re-imported the same clips, using both RGB and 601 levels.  So for each of the 2 basic test clips there are 4 variations.  These were compared to the original test clips visually and with the colour corrector in Avid, using the eyedropper to sample pixel values.

    --------------------------------

    Here’s a table of the results that lead me to my conclusion.  I limited my testing to DNxHD220x and ProRes HQ, but imagine the results would hold for other codecs in the same family.

    The DNxHD results are as expected.  I have highlighted the 2 cases in this table where the ProRes results differ from the DNxHD.  In both cases, it appears the ProRes results ignore the export checkbox being set to 601, and are identical to RGB exports.

     

    Codec

     

    Export from Avid

     

    Quicktime display

     

    Re-import to Avid

     

    Compare Levels in Avid – re-import vs original

     

     

     

     

     

     

     

     

     

    DnxHD 220x

     

    RGB

     

    Clipped and stretched *

     

    601

     

    Unchanged

     

     

    601

     

    Full range (unchanged)

     

    601

     

    Unchanged

     

     

     

     

     

     

     

     

     

     

     

    RGB

     

    Clipped and stretched

     

    RGB

     

    Gamma correct, clipped **

     

     

    601

     

    Full range (unchanged)

     

    RGB

     

    Nothing clipped, range squeezed ***

     

     

     

     

     

     

     

     

     

    ProRes HQ

     

    RGB

     

    Clipped and stretched

     

    601

     

    Unchanged

     

     

    601

     

    Clipped and stretched

     

    601

     

    Unchanged

     

     

     

     

     

     

     

     

     

     

     

    RGB

     

    Clipped and stretched

     

    RGB

     

    Gamma correct, clipped

     

     

    601

     

    Clipped and stretched

     

    RGB

     

    Gamma correct, clipped

     

     

     *Clipped and stretched – indicates values have been truncated below 16 and above 235, then stretched to the range 0-255.

    ** Gamma correct, clipped – no values exist above 235 or below 16, but everything in between is unchanged.

    *** Nothing clipped, range squeezed – the full range of values 0-255 have been scaled into the range 16-235.  So no values exist above 235 or below 16, but nothing has been truncated.

     

    Other conclusions / speculations:

    It seems likely the RGB/601 setting for Avid quicktime exports just sets a flag in the quicktime file -- no pixel values are actually changed in the file during output.  If this were not the case, then it would take longer to output an RGB file as 601, or vice-versa, when in practice, quicktime output seems to take the same length of time regardless of the RGB/601 output setting.

    When 601 is set on import, it overrides any RGB flag setting in the quicktime file, allowing access to the full range of original pixel values.

    When RGB is set on import Avid actually changes the pixel values of the imported file, mapping 16 to 0 and 235 to 255, crushing all values below 16 and all values above 235.   The variations above 235 and below 16 are permanently lost.

    When importing, the Avid may not even read the RGB/601 flag it sets in the quicktime file, since the user always specifies how to interpret the levels on import.

    In these tests, After Effects shows the same results as desktop preview in the finder.  Presumably both access the quicktime files through the quicktime library.  So both pay attention to the 601/RGB flag correctly when displaying DNxHD quicktimes, and both treat ProRes quicktimes as always having the RGB flag set.  There is no mechanism in After Effects (so far as I am aware) that allows overriding the 601/RGB flag as Avid does when importing.

     

    Work: Media Composer 7.0.4, Mac Pro, 2 x 2.66 GHz 6-core Intel Xeon, 24 GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.9.2 <P> Home: MC 5.5.3 software... [view my complete system specs]
  • Sun, Sep 23 2012 7:19 AM In reply to

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    MBrock321:
    ProRes exports always behave as though they were exported as RGB
    ...when viewed in QT player....

    Media Composer /w Symphony option | PT-HD | Win7Pro64 HP | OSX MBP | ISIS5000 | Nitris DX | Artist Mix & Transport & Color | AJA T-Tap | Decklink... [view my complete system specs]
  • Sun, Sep 23 2012 7:34 AM In reply to

    • MBrock321
    • Not Ranked
    • Joined on Tue, Mar 1 2011
    • Posts 49
    • Points 605

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Not just in Quicktime player.

    If you export ProRes 601 and re-import it RGB you'll get different results than if you did the same thing with DNxHD footage.

    Work: Media Composer 7.0.4, Mac Pro, 2 x 2.66 GHz 6-core Intel Xeon, 24 GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.9.2 <P> Home: MC 5.5.3 software... [view my complete system specs]
  • Sun, Sep 23 2012 8:12 AM In reply to

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Ah, now I see. Thanks for the clarification.

    Media Composer /w Symphony option | PT-HD | Win7Pro64 HP | OSX MBP | ISIS5000 | Nitris DX | Artist Mix & Transport & Color | AJA T-Tap | Decklink... [view my complete system specs]
  • Sun, Sep 23 2012 5:17 PM In reply to

    • MBrock321
    • Not Ranked
    • Joined on Tue, Mar 1 2011
    • Posts 49
    • Points 605

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Here's a real-world example of how this could get you in the soup.

    Let's say you're trying to export footage to After Effects, manipulate it there, and re-import the results to Avid.  You want to retain your superwhites (over 235) and superblacks (under 16). 

    I would expect to be able to do this by choosing the 601 option when exporting my footage same-as-source. 

    If that footage is DNxHD, this will work properly -- I will get exactly the same pixel values in After Effects that I had in Avid.  If the footage is ProRes, it will be truncated and stretched inside After Effects, despite the 601 flag, and the superwhite and superblack variations will be lost.  If you don't realize that the levels in After Effects have been switched from 601 to RGB then you will also be very confused because the range will be wrong when you re-import your footage into the Avid.

    Work: Media Composer 7.0.4, Mac Pro, 2 x 2.66 GHz 6-core Intel Xeon, 24 GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.9.2 <P> Home: MC 5.5.3 software... [view my complete system specs]
  • Mon, Sep 24 2012 2:49 PM In reply to

    • Chuck Swan
    • Not Ranked
    • Joined on Sun, Jul 31 2011
    • Chicago / Milwaukee
    • Posts 48
    • Points 665

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Does this not also mean that this effect would be cumulative?  If you have to later round-trip again via ProRes, you would lose even more highlight and shadow data. Yes?

     

    MC 8.4.4, MacOSX 10.10.5, MacPro 6core 16GB RAM, GTX Titan X GPU, Apple 23", Apple 27", Avid Artist Control, Avid Artist Transport, Blackmagic... [view my complete system specs]
  • Mon, Sep 24 2012 3:07 PM In reply to

    • the_dark
    • Not Ranked
    • Joined on Fri, Aug 17 2007
    • Posts 165
    • Points 2,240

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Dell Precision T3600 Intel Quad Core Xeon E5-1607 3.06Ghz 8GB Memory (4x2GB) 250GB System Drive 500GB to 1TB Media Drive nVidia Quadro 2000 Dell... [view my complete system specs]
  • Mon, Sep 24 2012 4:23 PM In reply to

    • MBrock321
    • Not Ranked
    • Joined on Tue, Mar 1 2011
    • Posts 49
    • Points 605

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Chuck Swan:

    Does this not also mean that this effect would be cumulative?  If you have to later round-trip again via ProRes, you would lose even more highlight and shadow data. Yes?

     

    You could avoid any cumulative effect by importing your After Effects render back into Avid with the RGB flag set.  This would map values back to the 16-235 range.

    Work: Media Composer 7.0.4, Mac Pro, 2 x 2.66 GHz 6-core Intel Xeon, 24 GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.9.2 <P> Home: MC 5.5.3 software... [view my complete system specs]
  • Mon, Sep 24 2012 4:24 PM In reply to

    • MBrock321
    • Not Ranked
    • Joined on Tue, Mar 1 2011
    • Posts 49
    • Points 605

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    the_dark:

     

    Thanks for the pointer to After Effects colour management -- good to know.

    Work: Media Composer 7.0.4, Mac Pro, 2 x 2.66 GHz 6-core Intel Xeon, 24 GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.9.2 <P> Home: MC 5.5.3 software... [view my complete system specs]
  • Thu, Sep 27 2012 6:36 PM In reply to

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    I also found this "bug" 2 weeks ago and reported it to Avid.  It is my guess that Avid is exporting ProRes footage as "RGB" regardless of what you select.  

    Home: 2012 rMBP 2.6ghz, 16GB RAM, OSX 10.10.5, MC 8.4.1 || Work: HP Z400, Win7 Professional, MC 6.5, ISIS/Interplay @danielfrome on twitter [view my complete system specs]

    Avid GoPro

  • Tue, Mar 5 2013 12:43 AM In reply to

    • Andrew_G
    • Not Ranked
    • Joined on Tue, Jul 5 2011
    • Posts 13
    • Points 145

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Has anything been done about this issue?

    I'm trying to export some ProRes 422 HQ Quicktimes for a distribution company and I always end up with what seems like this same RGB behaviour upon export (my blacks are getting crushed).

    Does anyone know of a solid way to convert DNxHD quicktime to ProRes without getting the crushed blacks?

    So far, I've tried Mpeg Streamclip, QT pro, Media Composer, Squeeze, etc. All of these conversions have given nearly the same result (crushed blacks).

    Is this a flagging issue or are DNxHD and ProRes just such drastically different codecs?

     

    -Andrew

  • Wed, Mar 6 2013 8:15 AM In reply to

    • MBrock321
    • Not Ranked
    • Joined on Tue, Mar 1 2011
    • Posts 49
    • Points 605

    Re: Same-as-source quicktime exports - ProRes and DnxHD differ

    Maybe this has been fixed in version 6.5, since ProRes has been turned into a 'native' codec?  I'm still on 6.0.3, so I can't say.

    Try the following, if you have ProRes material inside Avid.  (If you're starting from DNxHD, transcode to ProRes first).

    1. Export ProRes as a Same-as-source quicktime with 601/709 levels.

    2. Create an After Effects project that is 32 bpp, with Colour Management Working Space (in project settings) set to "HDTV (Rec 709) 16-235."

    3. drag your exported ProRes quicktime into the After Effects project, dump it into a new comp, and render it out as a new ProRes quicktime.  In the output settings Color Management pane, use the following settings:

      - convert to linear light - on for 32 bpc

      - Output profile - Working Space - HDTV (Rec 709) 16-235

    The resulting output should look correct (in Quicktime Player 7, at least) but I would recommend confirming it looks the way you think it should in your application of choice.

    Worth noting that if you AMA the After Effects output file back into Avid, it doesn't look correct unless you go into source settings and choose 'stretch video to graphics levels'.

    Work: Media Composer 7.0.4, Mac Pro, 2 x 2.66 GHz 6-core Intel Xeon, 24 GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.9.2 <P> Home: MC 5.5.3 software... [view my complete system specs]
Page 1 of 1 (12 items)

© Copyright 2011 Avid Technology, Inc.  Terms of Use |  Privacy Policy |  Site Map |  Find a Reseller