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Reducing filesize from DVD

Discussion in 'DivX / XviD' started by jackrf, Dec 9, 2002.

  1. jackrf

    jackrf Member

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    I was ripping/converting 4 episodes of a show. First one worked fine and had a small filesize, but the second 3 all had massive filesizes (750 megs.) I watched them in Windows Media, and it said the 2nd 3 had a bitrate of 1411, and the 1st one 160. I entered in the same bitrate in Virtualdub, though. Does anyone know why this is happening? Thanks for any help.
     
  2. bang

    bang Member

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    You didn't give many details (codec, clip length, what the clip is, clip resolutions etc). Possible answers, the clips are simply longer, are higher quality (therefore higher bitrate), have move fast action sequences (again bitrate goes up), use a different codec, may have uncompresse audio, have higher resolution etc.
    Anyway you say 750mb is a lot. For MPEG-4 at DVD res, and 30 min of movie, 750mb you mean high quality. But in MPEG-2 or MPEG-1, that would count as highly compressed.
    One note: Windows Media gives you few details about a clip, and most of the time they are wrong as well. You're better of using file info through VirtualDub
     
    Last edited: Dec 9, 2002
  3. jackrf

    jackrf Member

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    ok, I was using DivX 5.0.2 Pro codec, about 43 minutes in length. I was using 640x360 resolution for all. My main concern was that the bitrate i calculated didnt work. I used 1427 for all (DVtool said this would keep it to 500 Mb), but the last 3 were way too high for some reason. I have a feeling I missed a step, but i double-checked. Thanks again for the help.
     
  4. bang

    bang Member

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    Listen, all those bitrate calculators are bullshit. The only program that always gives very accurate bitrates is TMPGEnc, but TMPGEnc doesn't do MPEG-4 (but eventually, once MPEG-4 does become an ISO standard, it probably will).
    Now, the problem with MPEG-4 is that it is variable bitrate, it doesn't give CBR (and if it did, it would defeat the purpose of there being MPEG-4). Constant quality is generally a higher priority in MPEG-4 codecs, so that's why the fluctuations in bitrate. Now 1440kb/s is roughly what you are after and the only way to get that as the average is by two pass encoding using divx 5.0.2, but the other way is to use Divx 3.11a fast motion codec in all its highest settins. That codec has been edited so it will find the best quality/size ratio. Most movies (encoded with it) will fit onto one CD, even if in full dvd resolution.
    Note for the fast motion codec: It must have the scene detect patch, and all the settings should be set to there highest (9999 keyframe, 100 quality, 6000k bitrate) so that the codec has the most options to work in.
     
    Last edited: Dec 10, 2002
  5. herbsman

    herbsman Moderator Staff Member

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