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  1. Member
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    Youtube changed the color on my video. The left is the original Mpeg4, while the right is the uploaded version played on youtube. Not only is the yellow off, but the youtube version plays much darker and oversaturated compared to the original. What happened?


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  2. Member budwzr's Avatar
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    Your video is "Out of Gamut" with YT's compression algorithm.
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  3. Member hech54's Avatar
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    Do people talk just to hear themselves talk?
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  4. Member budwzr's Avatar
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    Oops!
    Last edited by budwzr; 8th Jan 2011 at 22:02.
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  5. I had time to run a little test. I took yellow image on the left and applied the following AviSynth script:

    ConvertToYV12(matrix="pc.709")
    ConvertToRGB(matrix="rec709")
    I then overlaid that image onto the original below the right yellow image:

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    As you can see the colors match very closely (although the levels are a little off). So the evidence is very good that the difference is which color matrix is being used by the player and youtube (or the flash player).
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    Thank you Jagabo, for taking time to reply with so much information.
    What can I do to make the color show up accurately on youtube? Or is this a limitation of youtube? It is interesting that you are able to replicate the problem by running a script.
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  7. Are you sure youtube is the problem, not your player/editor? What is your source? Is the colorspace flagged within it? If not, is it high definition or standard definition? The general rule when colorspace is not flagged is: SD uses rec601, HD uses rec709.
    Last edited by jagabo; 9th Jan 2011 at 05:48.
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    I am not sure what is going on. My video guy that I hired said the video is mpeg4, the videos are 720 and 1080 (I have both). He said the colorspace is RGB. My video files are .MOV.
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  9. Member budwzr's Avatar
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    Just out of curiosity, when you download the .mp4 from YT and play it locally on your player, what do you get?
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    I didn't think it was possible to upload to youtube which compresses it, and then save the compressed version back on my PC. I only got to watch it on youtube. Am I missing the feature?
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  11. There are many ways to download Youtube videos. FireFox with the Download Helper plugin, for example:

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    There are also web sites that will do it for you. Go to this web site and enter the URL for your video:

    http://keepvid.com/

    Originally Posted by thurnau View Post
    He said the colorspace is RGB.
    He may be working in RGB but when he compresses the video (h.264?) for the MOV file the codec uses YUV with 4:2:0 chroma subsampling internally. Ie, it converts RGB to YUV with one of the aforementioned matrices. When Youtube receives your upload they recompress it. I'm not sure what they do about color -- whether they pay attention to the colorspace flag or if they just use a particular matrix.
    Last edited by jagabo; 9th Jan 2011 at 22:53.
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  12. Member budwzr's Avatar
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    Originally Posted by thurnau View Post
    I am not sure what is going on. My video guy that I hired said the video is mpeg4, the videos are 720 and 1080 (I have both). He said the colorspace is RGB. My video files are .MOV.
    They are not Mpeg4, they are H.264 or Sorenson. Mac H.264 is a different animal from the PC H.264 world.
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    Using the Keepvid link the FLV high quality version and the MP4 high Definition was still yellow instead of orange shade of yellow in the intro and slightly over saturated and too dark in the video.

    I will recheck the format on my email from the video guy.

    This is a link to the youtube videos. I kept them as private because I didn't want them to get popular until I solve the color problem.
    http://www.youtube.com/watch?v=smVyFU6YzZQ
    http://www.youtube.com/watch?v=avPDTlK2Rmo
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  14. Member budwzr's Avatar
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    So that means it's not YT's fault.

    FLV = On2 VP6 codec.
    MP4 = H.264

    Both give the same results. To me that means the original has colors that don't translate. I'm going to lay the blame on Apple.
    Last edited by budwzr; 10th Jan 2011 at 00:33.
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  15. Both the 640x360 FLV and the 1280x720 MP4 I downloaded (both AVC) had the brighter yellows when viewed locally. Using AviSynth's Histogram() shows the two files contain (YV12) luma values outside the normal 16-235 region:

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    This is a graph of the brightness of the video, scanline by scanline, summed into one graph. The yellow peaks and valleys in the brown bars shouldn't be there. They should be completely within the black area.

    I'd have to see the original MOV file to say exactly what happened. But this appears to be just a RGB/YUV matrix problem. Maybe the original upload was PC RGB (0-255) and was converted to YUV assuming it was studio RGB (16-235).
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  16. I agree with budwzr - Looks like the quicktime gamma shift bug . You're on a Mac using QT, which means what you perceive as your original is actually "wrong" or displayed incorrectly . 99% of the industry uses 2.2 gamma, QT doesn't. If you upload a sample of the original this can be confirmed.

    Youtube maybe partly at fault, it displays using Rec.709 for both SD and HD - This may or may not match what your video guy had in mind in his workflow
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    What should I tell my video guy Fire on the Bayou to do to get the color right?
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  18. In quicktime X and FCP , I think there is an adjustment for display gamma to match the correct display settings. I would use those for color correcting, grading and previewing. I would ask in the Mac forum for specific advice. Older versions of quicktime do not have this correction

    The color is "right" on youtube in a sense. Ie. it's displaying Y'CbCr HD material doing the RGB conversion using ITU Rec.709 - which is the industry standard for broadcast. It's just that what you see locally in QT Player - and what "think" is right.... is wrong.

    You can look up "quicktime gamma shift bug" or similar terms, there should be 1000s of posts on this. It's very well documented
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  19. The YouTube videos have luma values way outside the 16-235 range. I doubt the OP's source has that problem. But with seeing it there is no way to say for sure.
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  20. You could be right jagabo, IIRC, youtube decodes some formats using full range. e.g. MJPEG in MOV from some point and shoot cameras. But I doubt this his source uses MJPEG


    Can you upload a sample of the source video thurnau?
    Last edited by poisondeathray; 10th Jan 2011 at 09:16.
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  21. Another problem here is that the images have different colors here at VideoHelp. Ie, the thumbnail in the OP's first post has different colors than when you click on it to see the full size image. There are so many variables it's impossible to say what's right and what's wrong and where it's going wrong.
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  22. That's true, many variables, but the original sample will tell for sure.

    I downloaded the YT flv video, and rewrapped into .mov with ffmpeg, played with QT

    Left is YT, Right is the same YT video played in QT 7 . (Picture is not hosted by this forum)




    And here is with the gamma shift workaround (now QT player displays video as it should)
    Left is original, Right is with gamma shift fix

    Here is one of the many workarounds
    http://www.videocopilot.net/blog/2008/06/fix-quicktime-gamma-shift/

    Last edited by poisondeathray; 10th Jan 2011 at 10:15.
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  23. QT was banished from all my computers long ago.
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  24. Originally Posted by jagabo View Post
    QT was banished from all my computers long ago.
    Probably for good reason .

    But the "bug" exists on MAC platform as well! And they've known about it for years. Only now have they started to do something about it. In the newest version of QT OS X you can adjust gamma and FCP compatiblity. Apple is primarily a hardware company, they don't care as much about improving software. They want to sell you the latest ipod/pad/thingy
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  25. But the Mac just works!
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  26. Originally Posted by jagabo View Post
    But the Mac just works!

    but can't we just be friends





    @thurnau - BTW - This doesn't proove anything, it's just a demonstration of the gamma bug. We still need to look at the original video, or at least use mediainfo mac to post information about the video
    Last edited by poisondeathray; 10th Jan 2011 at 11:03.
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  27. There's one other issue that hasn't been discussed. I don't know if it applies to the Mac. Under Windows, media players (like WMP, MPCHC, VLC, KMPlayer, etc.) usually send YUV sources as YUV to the graphics card and the graphics card converts to RGB using its proc amp settings (separate from the Desktop color settings). But flash players in a browser convert to RGB in software then send RGB to the graphics card. So the exact same video can look different playing in a flash player vs. playing in a media player.
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  28. Member budwzr's Avatar
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    My approach is more pragmatic. Experience shows that anything "Apple" has been factory tweaked to give the illusion of "better", whilst maintaining the crucial divide necessary to differentiate the product.

    In layman's terms: You can count on Apple to convolve everything. It's in their genes to NOT play well with others.
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