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2-Pass Encoding in VirtualDub

Discussion in 'DivX / XviD' started by tommcd, Apr 17, 2002.

  1. tommcd

    tommcd Guest

    I am not so much having a problem with this, I think I am just misunderstanding something.

    When I follow the instructions on "Copy your DVD into DivX5 format" at the end I end up with 2 files, a little one (usually about 100Mb) for the first pass, and a big one (usually about 900Mb) for the second pass.

    The biggest file plays in the DivX player, is this the combined file?, I had assumed VirtualDub would combine first and second passes, save the result as something different and delete first two files. Am I wrong about that?.

    Also, does anyone else find the DVtool bitrate calculator pretty inaccurate?, I told it my movie details and that I wanted the final filesize to be 1400Mb and it told me to use a bitrate of 2115, this resulted in a file of 929Mb, even upping the bitrate to 3000 only resulted in 959Mb, DVtool's guess was way out. Is there a better (one that gives me numbers that actually work) bitrate calculator I can use?

    Thanks in advance,

    Tom
     
  2. dRD

    dRD I hate titles Staff Member

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    DVTool doesn't have the problem, DivX5 has -- somehow DivX5 doesn't obey the bitrate you set for it in certain cases, specially when creating big DivXs.

    And as far as the 1st pass/2nd pass thing goes:

    First pass: the encoder (DivX5 codec) goes through the movie and determines frame-by-frame how "complex" the content is (i.e. fast action scenes are complex, slow romantic sunset scenes are "easy") and stores information for each frame to the first pass file. This is just a guidance file and doesn't actually hold any video itself.

    Second pass: Now encoder goes through the movie again, this time using the logfile (1st pass AVI) to determine the frames that need higher and frames that need lower bitrates and encodes the final video.
     
  3. Wiener

    Wiener Guest

    Does the 2 pass offer much improved quality?
    I've been using the 1 pass quality with the value set to 5 or 6 and quality of the AVI looks great. How long does each pass take. I know it takes about 7 to 10 hours on my P3-600 using the 1pass quality setting.
     
  4. dRD

    dRD I hate titles Staff Member

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    2-pass definately offers much better quality and is recommended always.
     
  5. OvClockd

    OvClockd Guest

    2nd pass takes about half as long as 1st pass. and with Divx 5 DVtool is off, i just encode 4 mins segments of the movie and add the Data Rate to the mins of the movie,, i also find it easier to not encode audio. do that after the 2nd pass is finnished, use Nandub. only takes me about 2mins to add audio.

    i always use AC3 audio. with the high quallity of Divx5 theres no need to use Mpeg-Layer-3 audio.
     
  6. kmart

    kmart Member

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    I'm having the exact same problem...I posted a very similar thread just before.

    dRD, "DivX5 doesn't obey the bitrate you set, especially when creating big DivXs"...Is there any way around that? Should I just settle for the 767 MB file? That sounds like a really big problem, is there any fix for it or something?
     
    Last edited: Jul 9, 2002
  7. dRD

    dRD I hate titles Staff Member

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    kmart: Two options at the moment, none of them is ideal, unfortunately: try encoding with XviD instead (no, we don't have a guide nor the codec yet) or settle with one CD DivX.

    The problem is really with DivX that "saturates" at some point, in around 1GB for 100min movie, depending of course on the movie material.
     
  8. kmart

    kmart Member

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    Well not having the Xvid guide would make things difficult for me, but wouldn't not having the Xvid codec make it impossible to encode a movie in Xvid. I mean, from what I understand about the words "codec" and "encode" wouldn't one need an Xvid codec to encode Xvid? :)
     
  9. dRD

    dRD I hate titles Staff Member

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    Sorry, I meant _we_ == AfterDawn.com, don't have the codec for download. Of course it is available on the Net, just use the google.

    And doom9.net should have some sort of XviD guide -- basically only thing what you need to do, is to change DivX part with XviD and learn its settings, otherwise our old guide should be just fine.
     
  10. kmart

    kmart Member

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    Well, how do you feel about Xvid? Doom9 kind of goes through all the positives and negatives of the other codecs, but they don't really mean anything to me, as I do not understand them and the weight that each positive/negative should carry. Do you need to install a separate decoder to play Xvid movies? I mean, part of the reason I'm ripping/encoding is so I can share these movies...I don't want to start messing around with another format.

    Also, if I install the Xvid codec, will it automatically appear in virtual dub like divx 5 does? Does Xvid encoding have comparable quality to Divx 5? I'm not going to use Xvid just for the sake of taking up more space...I want to also get the increased quality that is supposed to go along with more space. Also, when I went to xvid.org they were talking about their codec "binaries". I didn't really look into it too hard, but I don't want to mess around with compiling it and stuff. I'd rather keep it simple.

    I guess I'll go look into some of this stuff on my own.
     
    Last edited: Jul 9, 2002
  11. dRD

    dRD I hate titles Staff Member

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    XviD, what I've understood, compares very well with DivX's quality and in some cases even beats it.

    And both codecs are based on MPEG-4 standard and they should be able to decode (==play) each others just fine. This means that machine that has DivX5 installed on it, should be able to play XviD videos without any trouble whatsoever and vice versa.

    Best option anyway is to install FFDShow for playback as it is much faster than DivX5's playback. (yes, it can be downloaded from our site :)

    ...and the binaries are the ones you need.
     
  12. kmart

    kmart Member

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    According to some chart I read, XviD does not have Quarter Pixel, GMC, or Bidirectional Encoding, all three of which is recommended to be used in encoding with divx 5. If XviD does not have these options, whatever they are exactly, am I missing anything? Is it worth giving up if it means I'll be able to encode at nearly double the bit rate? What are these options exactly; what am I sacrificing by not having them when I encode in XviD?

    I have virtual dub running right now, with the XviD options up, waiting for the word.

    Also, according to Vdub, XviD has no restrictions as opposed to DivX which says height must be a multiple of 16. Does this mean the height in XviD can be anything? Do I need to make the height a multiple of 16 to ensure playback compatibility in DivX?
     
    Last edited: Jul 9, 2002
  13. dRD

    dRD I hate titles Staff Member

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    I would say that you should go with base-16 height and width just to be sure (also some graphics cards play the material faster / better if the video is in multiplies of 16).

    And what can I say other than "try it and see if the quality satisfies you" and of course, tell us whther you liked the results or not :)
     

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