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MPEG-2 Conversion & RGB Color Source Issue

Discussion in 'Convert video to another format' started by Droogie1971, Mar 16, 2012.

  1. Droogie1971

    Droogie1971 Member

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    Hi there,

    I have a really annoying problem that the post house I'm working with can't seem to figure out. Hopefully someone here can help me...

    My online editor delivered my project as an uncompressed Quicktime file in an RGB colour space 0-255. When the post house compresses the file using the MPEG-2 codec in Cinema Craft for DVD duplication the image comes out extremely crushed on HDTVs and on computer screens. Dark blacks just completely lose all their detail and become just a mushy wash of black. They tried this twice, at first with the option 16-235 (as they didn't know it was an RGB colour source) and then a second time using 0-255. Both times had the same result.

    When I import the file into Final Cut and change the colour space settings from YUV to RGB it appears fine. And when I export a Quicktime file of this test it looks great in Quicktime player on my computer. However, as soon as I go to convert the file using the MPEG-2 codec the same thing happens and it gets crushed.

    Anybody have any experience with this? Please help! Thanks!
     
  2. hello_hello

    hello_hello Member

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    Not having ever used Cinema Craft I'm not sure I've got my head around this correctly, but....

    I'd assume for whatever reason the levels aren't being converted to 16-235 when encoding, and the encode is being played under the assumption it's levels are 16-235, and of course everything's too dark.

    "They tried this twice, at first with the option 16-235 (as they didn't know it was an RGB colour source) and then a second time using 0-255. Both times had the same result."

    I'm not really sure what the point of the option is if it doesn't actually convert the levels. Maybe it only applies to encoding YUV sources rather than RGB.

    If I was converting the video myself, I'd find a way to manually convert the levels during the encoding process, but I'm not sure how I'd go about it with your file as I'm not sure what an uncompressed QuickTime file actually looks like (RGB in an MP4?) and I've not used either Cinema Craft or Final Cut.
    A lot of the free software available for encoding video uses AVIsynth as the frame server, and it shouldn't be too hard to use AVIsynth to convert the levels. Or VirtualDub has an internal filter for adjusting the levels. In fact if you're encoding via DirectShow I think even ffdshow could do it.

    Are you able to upload a sample of the video in question to somewhere such as MediaFire? If nobody else has any clever ideas I could at least have a play around to work out how I'd convert the levels if I was doing it myself.
     
  3. Droogie1971

    Droogie1971 Member

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    Thanks a lot for your detailed response. Its much appreciated. I dont know how to manually convert it from an RGB source to a YUV. Ive checked for formulas online but it all looks pretty complicated and I dont have the software to do it. Ill check out AVIsynth and VirtualDub to see if it gets me anywhere.

    In the meantime, Ive uploaded two examples to MediaFire to show you the issue Im having. One file shows you what the clip looks like before it goes through the Mpeg-2 compressor and the other shows the after effect. Here's the link -

    mediafire.com/?mmf7o6qy81598e3

    Thanks again for your help!
     
  4. hello_hello

    hello_hello Member

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    Unfortunately I didn't have any luck with your original sample. Being a PC user when it comes to mov files....

    I tried remuxing it as an MKV with MKVMergeGUI so I could work with it, but got the error message:
    "Warning: Quicktime/MP4 reader: Unknown/unsupported FourCC 'AVdn' for track 0".
    I tried a different converter but still had no luck and I have a plugin installed to let VirtualDub open mov files, but it didn't like the sample either.

    According to MediaInfo however, the uncompressed sample is actually YUV, not RGB. If MediaInfo is correct (it might not be) and the original is YUV (0-255), that might explain why the levels need to be changed manually when encoding, but as I couldn't find a way to view your sample on the PC I couldn't compare it to the encoded version (which I could view without a problem).

    I'll admit I'm far from an expert. I generally just encode stuff and if the levels are wrong or the colors off then I usually know what fix needs to be applied and how to do it but it doesn't mean I always understand "why" I need to do it, if that makes sense.

    The sample you uploaded, can you decode it okay on a PC? Sorry I couldn't be of any more help as yet.
     
  5. Droogie1971

    Droogie1971 Member

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    Thanks a lot for all your help. It's much appreciated.

    I'll keep trying!
     

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