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FairUse 1600MB instead of 1400MB - how come?

Discussion in 'DivX / XviD' started by jlrm365, Jan 15, 2007.

  1. jlrm365

    jlrm365 Regular member

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    Hello.

    I am aware of the lengths of movie which should be, according to the conventions of those who establish these sort of conventions, converted to single CD size and those which should be converted to double CD size.


    I use FairUse 2 and these are my default settings: HERE


    As you can see, I convert double CD sized movies in one piece, because I store them for myself and not for vcds / upload / anyone else. I also drop 1MB, to make sure of fitting (though this is often not needed).

    Some movies convert to 14??MB (the ? representing an arbitrary number), as they are meant to. What is odd is that, despite the default settings that you can see, I have converted some which end up at about 16??MB in size.

    How come? I do not convert overly large movies. Indeed one I just converted to 1600MB was only 1:37 in length. I am not converting anything that appears too big and my settings should be correct. Some with subtitles convert to the expected size and some without them do not. I cannot see an obvious answer.

    I do not want to have to drop down the file sizes and convert, trial and error fashion, for certain conversions - that would end up in poorer quality and constant tinkering.

    What has caused my issue and what can I do about those particular conversions which end up oversized, so that another conversion of the same movie ends up the "correct" size?

    Thanks.
     
  2. Indochine

    Indochine Regular member

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    When you convert a movie from DVD format to AVI, the target size is just that - a target. Sometimes the source material just won't compress well. I see you are using 2 pass mode which is good.

     
  3. jlrm365

    jlrm365 Regular member

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    So it sometimes just doesn't go, eh? Ok.

    In that case, is there any tool to recode avi files, to reduce their size? I am aware of recoding sound, but not to a degree that would make as much of an impact as 200MB. I prefer not to recode either audio or visual on its own.

    Shampoo takes a whole DVD and shrinks it, but is there something that can take a whole avi file and proportionately shrink everything (rather than just sound or just visuals)?

    I store several avi files on one DVD and take those with me when I travel, so it's not a huge issue, but it would be nice to keep everything uniform if possible.

    Thanks.
     
  4. Indochine

    Indochine Regular member

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    The problem is to do with the way that the divx encoder manages to shrink data. For that matter, the same type of problem arises with compressing wav files to make mp3 files.

    What happens when you are building a compressed file is (this is very simplified) that you examine the first frame, then you examine the second frame. You record the first frame data in full in your compressed file. Then you compare the second frame with the first frame, and record the differences. You go on like this, recording the differences. Every so often you record a full, "key" frame and start all over again.

    Obviously, a video where every frame is the same is going to compress very well. Real world movie files are not like that. They have color, movement, brightness changes. Some more than others. In the early days of Divx there were separate "low motion" and "fast motion" codecs. So it is not possible beforehand to say, "Please Mr compressor, make me a file of exactly 700 MB".

    If you have access to the divx codec options you can choose a more lossy profile and lower the bitrate. I don't know if FairUse allows access to the codec settings. Also, you can encode the sound at a lower bitrate.

    Come back and let me know how you get on.






     
  5. celtic_d

    celtic_d Regular member

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    Pfffft.

    Doesn't matter how poorly something compresses. Set the bitrate to 900k to hit 1400MB's and you get 1400MB's. If something doesn't compress well, then you just get poor quality. Has no bearing on hitting the filesize or not.

    Your problem probably relates to compressing too well. Your filesize for the first pass would be under 1400MB's (taking audio into account). Now looking at my installer which is based on the official one (not sure if you are using my build or not) FU uses the default quant capping of min=1, so when you have a 2nd pass larger than the first, it (Xvid) tries to increase the filesize by inserting quant 1's. Problem is that with the default overflow settings it often ends up inserting too many q1's and oversizing. Wouldn't recommend using quant 1's anyway. Better to increase the resolution instead. Think in such a case AutoGK just disables bframes and re-runs the 1st pass.

    Assuming FU leaves the stats file (can't remember), then you could varify my theory.

    The values are @
    HKCU\Software\FairUse Wizard 2\Default Profiles\XviD 1st pass
    min_iquant, min_pquant, min_bquant
    Set to 2 and you should just get an undersized file, since without quant 1's, you can't have a larger 2nd pass than the first.

    People complaining about undersized encodes was actually the reason why the defaults were changed from 2 to 1 though.
     

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