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Activity Forums DVD Authoring Can someone explain to me audio delays when demuxing DVDs??

  • Can someone explain to me audio delays when demuxing DVDs??

    Posted by Juan manuel De anda jr on January 12, 2010 at 3:44 pm

    Seems to me every program I use to demux DVDs results in two files that are not in equal length.

    Is there a reason for this? Is it a video issue? an audio issue?
    Has this always been a problem?

    I can’t seem to find anything online that explains this thoroughly. Most places just assume I should already know what the problem is and goes right into talking about fixing it.

    Well what are these delays? What causes them?

    Any help would be greatly appreciated.

    You see, At work I often have to edit audio off of pre-recorded DVDs. (redactions you could say, and no, I have no choice of the material given to me, I just have to work with it)

    It would be much faster if I could rip the audio file, make my edits, and then mux it back into a new DVD. But I don’t find this to be reliable AT ALL.

    Ripping the the a/v together is often not that reliable either, and I end up doing a live uncompressed capture. Compressed files are junk for video editing anyway.

    Well, I was just hoping someone around here would have some knowledge on the situation. So far I just don’t see short cuts working and will stick to the true and true if not shortest method.

    This is my first POST!

    Juan manuel De anda jr replied 16 years, 3 months ago 2 Members · 4 Replies
  • 4 Replies
  • Roman Melekh

    January 12, 2010 at 9:31 pm

    there is multiplexing system of DVD – audio blocks and video blocks muxed depending of bitrates, number streams etc…
    and you can get video start to 0:00:00:00, but audio1 – +200ms, audio2 – +170ms etc..
    this is normally

  • Juan manuel De anda jr

    January 12, 2010 at 10:40 pm

    So it is normal to have those audio delays? And once you separate the a/v you get rid of that delay? Is that why the tracks no longer match in length?

    What is the intent of having the delay in the first place if I may ask?

  • Roman Melekh

    January 13, 2010 at 8:07 am

    I use DVDDecryptor for demux DVDs. After demux i have files
    aaaaaaa.m2v
    bbbbbbb delay +NNN.ac3
    ccccccc delay +MMM.ac3
    etc…after this i use DVDLAB’s tool for ac3/dts/pcm sync – open file, set delay, get 100% sync file.

  • Juan manuel De anda jr

    January 13, 2010 at 2:00 pm

    that’s great but no one really answered my question. I want to know why the delays are there in the first place.

    I will however mess with the tools you suggested.

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