Latest post Sun, Dec 14 2014 5:54 AM by Marianna. 10 replies.
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  • Sat, Dec 13 2014 8:39 AM

    • lalittle
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    Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    I'm trying to fully wrap my head around the "flow" of what happens with the color space when I AMA link to mov files that were created using the DNxHD codec in TMPGEnc.  What I'm seeing is confusing me a bit.

    I'm creating DNxHD mov files (1080p 23.976 175x) from image sequences, some of which are full range 0-255, and some that are already in the 709 range of 16-235.  The movs created from the full range 0-255 stills end up in Avid spanning the correct 709 range of 16-235 -- i.e. at some point, the range was remapped.  The movs created from the 16-235 images, however, appear to have been "double remapped" to 709 space -- the blacks are way to high and the whites too low.

    This implies that somewhere along the line, the material is automatically remapped to 709 whether or not it needs it.  I'm trying to understand where this is happening since there is nowhere to "set" this parameter in either Avid or TMPGEnc.  In other words, there is no place to tell TMPGEnc whether or not to remap to 709 when making the DNxHD movs, and when AMA linking to DNxHD files, there are no "input" setting to tell Avid to expect RGB vs 709 range.

    My theory at this point is that TMPGEnc is doing some auto-remapping under the hood in order to show me what files are "supposed" to look like, even when displaying a 709 image on a computer monitor.  It appears to me that during the encoding process (TMPGEnc using the QT encoder and DNxHD codec) it is being assumed that the image files are always full range 0-255, and that the DNxHD encodes ALWAYS require remapping to 709.  Can anyone verify that this is the case?  Are DNxHD files always assumed to use 709 space by Avid/Quicktime/TMPGEnc?

    I can get everything to work as long as I always check the material I feed TMPGEnc to make sure it uses the full 0-255 range.  If it does not, I need to apply a YUV "CCIR601 expansion" filter on the image sequence before encoding.  This remaps the values to full range, so that when the DNxHD files are created, they end up back at the correct 709 range.  This seems like some unnecessary remapping steps, but it seems like the easiest solution at this point.  Am I understanding the process correctly?

    I'm unclear if the situation I'm seeing is an artifact of the way TMPGEnc works, or the way the QT encoding engine works.  Any insight on this would be appreciated.

    I'd also like to make sure that I'm applying the CCIR601 expansion filter correctly by moving both Luminance AND Color sliders to 255.  From what I've read so far it appears that this is the correct way to remap 16-235 values to 0-255, but I can't find all that much information on this.

    Thanks for any and all feedback on this.  I seem to be able to get it to work correctly, but I'd like to fully understand the process, and WHY I need to do what I'm doing.

    Larry

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  • Sat, Dec 13 2014 9:36 AM In reply to

    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    Larry, I have to say that after fully exploring this issue about a year ago, I gave up. TMPGEnc is an awesome program, but I could find no way to get it to not remap color levels when encoding to DNxHD. Maybe it's changed, but it doesn't sound like it. :(

    I wish I had better news for you.

    "When I spent 60k on a discreet edit digisuite system 10 years ago someone came up to me to offer fcp 2, I said it was a scam too." -Ric

  • Sat, Dec 13 2014 11:07 AM In reply to

    • lalittle
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    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    Thanks for the reply.

    Just out of curiosity, how did you deal with this?  It only comes up in certain circumstances, but I'm just looking for the best workflow.  Did you do something other than what I posted above, which was to use the "CCIR601 expansion" filter in TMPGEnc to remap the values so they ended up correct in Avid?  This adds an extra remap to the process, but the actual degredation of the image should be relatively minimal.  I can't change encoders at this point, so this seems like the most reasonable solution.

    I'm also still interested in confirming that the correct way to use the "CCIR601 expansion" filter in TMPGEnc is to set BOTH Luminance and Color sliders to 255.

    Thanks again,

    Larry

  • Sat, Dec 13 2014 5:10 PM In reply to

    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    I just gave up on the workflow I was trying to accomplish. :( Sorry I can't be of more help. :(

    "When I spent 60k on a discreet edit digisuite system 10 years ago someone came up to me to offer fcp 2, I said it was a scam too." -Ric

  • Sat, Dec 13 2014 7:23 PM In reply to

    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    tainI've made a feature request before to have the ability to override Avids assumption that certain codecs (like DNx) must be correct so can't be adjusted.

    We often see incorrectly created codecs and Avid should allow you to override and adjust as needed.

     

    TMPGeng is a great programme but it's flawed as you've experienced.

     

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  • Sat, Dec 13 2014 11:59 PM In reply to

    • lalittle
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    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    Pat Horridge:

    tainI've made a feature request before to have the ability to override Avids assumption that certain codecs (like DNx) must be correct so can't be adjusted.

    Given this statment, it sounds like I was correct that Avid always assumes that DNxHD files are 709.  I can work around this as long as I understand that it's happening, but I agree that it would be nice to be able to override the AMA link settings like you can with non Avid codecs.

    It appears that TMPGEnc is attempting to be "smart" and automatically make color space assumptions about certain files.  It does this with simply displaying files as well, like files from Blu-ray discs, which it always "displays" as full range even though they are 709 (i.e. the blacks always appear correct even though they use 709 speace and are displayed on a computer monitor.)  I think it does this for the sake of less knowledgeable people that don't understand 709 vs rgb color space issues.  These people might be confused by the milky blacks they see from a blu-ray rips, for example, so TMPGEnc "displays" these files so that they appear correct.  This isn't a bad thing to do -- Avid does this as well -- but unlike Avid, TMPGEnc does not give people control over it or indicate WHEN this is happening.  Doing this sort of thing "behind the scenes" in some cases but not others just makes things MORE confusing for people that DO understand color spaces.

    The obvious solution for color space encoding issues would be to have 601/709 vs RGB settings for both target AND source files in TMPGEnc.  This would allow people to deal with these issues without having to apply filters.  The program could still requre that people create DNxHD files as 709, but by allowing people to indicate what space the source file uses, it would remove the confusion in getting correct end results.

    We often see incorrectly created codecs and Avid should allow you to override and adjust as needed.

    TMPGeng is a great programme but it's flawed as you've experienced.

    Even with this issue, I still like TMPGEnc a LOT better than any of the other ones I've tried.  I've used a number of them, and TMPGEnc is the LEAST flawed in my experience.  I actually ended up using TMPGEnc due to more serious bugs in other encoders.

    Thanks again for feedback here, or for any further feedback on the earlier TMPGEnc "601 expansion" questions.

    Larry

  • Sun, Dec 14 2014 12:03 AM In reply to

    • Marianna
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    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    lalittle:
    I still like TMPGEnc a LOT better than any of the other ones I've triedl.  I've used a number of them, and TMPGEnc is the LEAST flawed in my experience.  I actually ended up using TMPGEnc due to more serious bugs in other encoders.

    Yes Yes Yes

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  • Sun, Dec 14 2014 12:17 AM In reply to

    • cuervo
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    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    Sorenson Squeeze is the only encoder I've encountered that allows one to select video range.

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  • Sun, Dec 14 2014 5:45 AM In reply to

    • lalittle
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    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    cuervo:

    Sorenson Squeeze is the only encoder I've encountered that allows one to select video range.

    Unfortunately, I encountered even more serious bugs and limitations in Squeeze.  In fact, Squeeze was the last one I was using before trying TMPGEnc.  I had been using Squeeze long enough that I had upgraded a few times, but after noticing that certain issues were not going away, I finally gave TMPGEnc a try.  I can't remember the exact specifics that made me switch, but it had to do with color/black level errors in Squeeze that I could not find acceptable workarounds for.  I was actually surprised to find that TMPGEnc solved the issues I was having.  Even though TMPGEnc has the issue discussed in this thread, it is more of a "limitation" than a "bug," and it's generally acceptable to me to work around it by using the "CCIR601 expansion" filter.

  • Sun, Dec 14 2014 5:46 AM In reply to

    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    Douglas,

    GREAT to see your name! :D I hope all is going well with you!!

    "When I spent 60k on a discreet edit digisuite system 10 years ago someone came up to me to offer fcp 2, I said it was a scam too." -Ric

  • Sun, Dec 14 2014 5:54 AM In reply to

    • Marianna
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    Re: Color space workflow questions when AMA linking to TMPGEnc DNxHD files.

    BobbyMurcerFan:

    Douglas,

    GREAT to see your name! :D I hope all is going well with you!!

    Geeked

    Thank you, Doing fine . . .  never looking back . . . . .  but dropping in here for the occassional comment.

    I started my own Forums for Gaijin-Eyes Tutorials a few months ago.

    If you are interested, email me and I will send you a link.

    Regards

    Douglas

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    marianna.montague@avid.com

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