about ogm to Xvid, VirtualDubMob & settop DVD player

Discussion in 'Amateur Video Production' started by Chong, Jun 27, 2004.

  1. Chong

    Chong Guest

    I know ogm is a container for mpeg4 and ogg/mp3 etc audio + subtitle. Is it
    correct to say ogm = Xvid? More specifically, if a settop DVD player is
    advertised to be Xvid/DivX capable, can I assume that it will play ogm? If
    I had a Xvid capable DVD player I would have burnt one and find out for
    myself. Unfortunately mine is on back order :(

    Using GSpot, I know the ogm contains a DivX5.0 video and Ogg Vorbis audio.
    Wanting to be sure that my ogm will play, I decided to convert it into Xvid.
    This is what I did:

    1. Open ogm in VirtualDubMob.
    2. Setup Xvid encoder using setting shown at
    http://www.dvd-guides.com/guides.php?category=dvdrip&name=xvid (step 6 - 8).
    3. Hit Save As... to recompress.

    The result was a HUGE > 2Gig Xvid file WITHOUT AUDIO! The size of the ogm
    file is only 700mb!

    Undaunted, I attempted to fix the audio problem by

    1. Open ogm in VirtualDubMob.
    2. Demux the audio track using VirtualDubMob. Ended up with an ogg file.
    3. Save the ogm file to an avi using "Direct Stream Copy".
    4. So I now have a DivX video without sound and a ogg audio file. I
    coverted the ogg into a wave since VirtualDubMob is not able to read ogg.
    5. Open audioless DivX video in VirtualDubMob. Add the wave file in "Stream
    List". Setup up Xvid encoder as per website mentioned above and start
    recompression using "Full processing mode".

    I still ended up with a > 2Gig Xvid file but with sound. OK I fixed the
    audio problem but the file size is still not right. Should have been around
    700mb. Any help or advise on the correct way to covert ogm to Xvid would be
    much appreciated. Thanks.

    Chong
     
    Chong, Jun 27, 2004
    #1
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  2. Chong

    Will Dormann Guest

    It would be just as correct as saying AVI = XVID.
    i.e., completely wrong.
    XVID is a codec, OGM is a container. Apples and Oranges.

    No.


    -WD
     
    Will Dormann, Jun 27, 2004
    #2
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  3. Chong

    Bariloche Guest

    AVI is a file format for audio + video streams, whatever the codecs
    for them. OGM is another format, wich can also carry subtitle streams,
    and whose audio is ogg; the video can be any codec.

    When a settop is said to be Xvid/DivX cappable, that means it plays
    XVid/DivX AVIs. Unless specifically advertised, it shall not play
    OGMs. Actually, I wonder if there is any DVD player that supports
    OGMs.

    So you need to make your OGM into an AVI. As you have already
    discovered, that means extracting the video and audio separately, then
    rejoining.

    If the video is DivX, you need not change it into XVid. Just do a
    Direct Stream Copy.

    As for the audio, you extract it as a Wav PCM. As this takes a lot of
    bitrate, you better encode it to Mp3 or Ac3 for the resulting AVI.

    As for the big size you got for the Xvid video, that depends on the
    bitrate used (if encoded in a constant or variable bitrate mode), or
    the quantizer (if encoded in a constant quality mode). Antoher thing
    you must notice is XVid does not support B-frames, while DivX does.
    B-frames encoding can reduce the file size about a 25%.
     
    Bariloche, Jun 28, 2004
    #3
  4. The audio doesn't need to be ogg. AC3, DTS, MP3, etc. is also fine.
    I'm not sure whether this is true. If you have a divx (which
    obeys the relevant profile) with CBR MP3 / AC3, without subtitles, I
    guess it plays in a divx player. I could be wrong however.
    This is very wrong. XviD does support b-frames.

    Wilbert
     
    Wilbert Dijkhof, Jun 28, 2004
    #4
  5. Chong

    Chong Guest

    Thank you all for your response. I'm fascinated by this video encoding
    technology. I am really amazed at the quality of the video that you can get
    from a 700+mb file. Would love to learn about the encoding algorithm. Have
    been capturing video and experimenting with video encoding a lot and is
    enjoying doing it tremendously. The only negative thing is there's lot of
    waiting (for the encoding process). Perhaps it's time to move up to a more
    capable machine.

    As for the huge final file size, the mistake was mine. Although I have set
    up parameters for the two passes correctly (I hope), I did not explicitly
    perform the 2nd pass encoding thinking that VirtualDubMod would do it
    automatically after completing the 1st pass. I now know I need to set up a
    job to perform the two encoding passes. The resulting file is 1Gig with PCM
    audio the major component. I will convert it to mp3 as suggested by
    Bariloche. Thanks!

    Cheers
    Chong
     
    Chong, Jun 29, 2004
    #5
  6. Chong

    Chong Guest

    I know what I did wrong to cause the huge file size - second pass encoding
    was not done at all! I did not know that the 2nd pass does not get executed
    automatically. Once I set up a job to do the 2 passes, the size came down
    considerably. The size shrunk quite a bit more when I converted the wave to
    MP3 as suggested by Bariloche.

    I'm fascinated by this encoding technology. It is really amazing the
    quality of video you can get from such a small file size. Have been
    capturing and encoding video a lot and is enjoying doing it. The only
    negative is there's lots of waiting (for the encoding process).

    Thank you all for your help.
     
    Chong, Jul 1, 2004
    #6
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