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Thread: ffmpeg from Jaunty to Karmic, Can't get the same quality!

  1. #11
    Join Date
    Apr 2007
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    13

    Re: ffmpeg from Jaunty to Karmic, Can't get the same quality!

    That's interesting, although it says adobe was fixed it in 10.1 and I
    have 10.1 installed now so that wasn't particularly the problem.

    Here's the link to the original:
    http://nickdeubert.com/media/picture...f/MVI_0010.MOV

    Also interestingly I was browsing the x264 source and saw this commit
    so I was going to retry it tonight and see if that made a difference
    for me: Fix
    two bugs in 2-pass ratecontrol


    Thanks for your help!

  2. #12
    Join Date
    Dec 2005
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    St. Petersburg, FL
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    Ubuntu 14.04 Trusty Tahr

    Re: ffmpeg from Jaunty to Karmic, Can't get the same quality!

    I think I've found the cause. It was tricky, since mediainfo wouldn't give the full option readout for the original, non-problematic file, but it has to do with the feature set used.

    The new default preset uses higher accuracy options, while the old default didn't. Most notably, the difference is CABAC (see: Wikipedia for more info) - the new -vpre default is High Profile and uses CABAC, the old version output Baseline Profile, which cannot use CABAC (it uses CAVLC instead). This is important, because CABAC is one of the biggest resource using features of H.264, although it does produce significant gains from the efficiency.

    As a test, run the new version of ffmpeg with the -vpre default option set, but add -cabac 0 -trellis 0 (or it might be -coder 0 instead of -cabac 0) after it and see if you still have problems with it being choppy.


    If it's anything other than that it'll be hard to diagnose because the 'good' file doesn't have its option readings stored in it like it's supposed to.
    Last edited by qyot27; December 16th, 2009 at 10:35 PM.

  3. #13
    Join Date
    Sep 2006
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    3,444

    Re: ffmpeg from Jaunty to Karmic, Can't get the same quality!

    Quote Originally Posted by qyot27 View Post
    I think I've found the cause. It was tricky, since mediainfo wouldn't give the full option readout for the original, non-problematic file, but it has to do with the feature set used.

    The new default preset uses higher accuracy options, while the old default didn't. Most notably, the difference is CABAC (see: Wikipedia for more info) - the new -vpre default is High Profile and uses CABAC, the old version output Baseline Profile, which cannot use CABAC (it uses CAVLC instead). This is important, because CABAC is one of the biggest resource using features of H.264, although it does produce significant gains from the efficiency.

    As a test, run the new version of ffmpeg with the -vpre default option set, but add -cabac 0 -trellis 0 (or it might be -coder 0 instead of -cabac 0) after it and see if you still have problems with it being choppy.


    If it's anything other than that it'll be hard to diagnose because the 'good' file doesn't have its option readings stored in it like it's supposed to.
    Excellent investigative work. I did a test with -vpre hq -coder 0 and it was still choppy, but the addition of -flags -loop seemed to do allow it to decode smoothly. Either of these commands should work:
    Code:
    ffmpeg -i MVI_0010.MOV -acodec libfaac -vcodec libx264 -vpre hq -coder 0 -flags -loop -crf 28 -s 1024x576 output-hq.mp4
    or:
    Code:
    ffmpeg -i MVI_0010.MOV -acodec libfaac -vcodec libx264 -vpre hq -vpre baseline -crf 28 -s 1024x576 output-baseline.mp4
    The first option should create a smaller file size, but I'm unsure if it requires more processing power to decode.

  4. #14
    Join Date
    Apr 2007
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    13

    Re: ffmpeg from Jaunty to Karmic, Can't get the same quality!

    Wow that seems to have fixed it! Thanks so much for your help guys!

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