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how can I avoid audio/video desync when converting a DVB mpeg2 source into AVI

Discussion in 'Digital TV - UK & Europe' started by dirinfo, Oct 22, 2003.

  1. dirinfo

    dirinfo Guest

    Do you record *.pva or *.mpg ? I use ProgDVB and let it do *.mpg
    As stated into the PVAStrumento help file, there are missing frames in video threads that leads to unsynch audio. But the PTS (timestamp) should allow to keeping the sound insynch..
    What is the method you DO USE at this time?
     
  2. R.Spark

    R.Spark Guest

    Hi dirinfo,
    I record using PVA format in Multidec, but ProgDVB and MPG will do it too I imagine (writing in PVA is not a matter of quality but of higher writing speed I believe, so that you reduce the risk of losing frames).
    I don't use PVAStrumento because I had some problems with it. I use PVA2MPG2 from Technotrend.

    I always have an audio delay when demultiplexing or converting directly to AVI. The problems lies in the mpg file, audio part, and NOT in VirtualDub.

    To correct this delay, the key program is DVD2AVI : when you save the project containing your mpg video, it saves automatically a .mpa audio file, in which the "magic value" of delay appears, for example :
    Vivement Dimanche MPA T01 DELAY -524ms.mpa

    Then, you have 2 solutions :

    1)either fixing the delay in the audio file, before converting your video. I use "AC3 delay corrector" by Daniel Ache

    2)or fixing the delay during the conversion, using the "delay" option in VirtualDub. Note that you have to enter the "magic value" manually.

    And that does the trick!!

    Hope it helps,

    Robin
     
  3. dirinfo

    dirinfo Guest

    Thank you Robin
    The method you descrive, is similar to what I do for DivX : (DVD2AVI + Gordian Knot) and now, GKnot knows how to treat an *.mpa stream and apply automaticaly the delay stated in the name given by DVD2AVI.

    My problem relies in the non compliant MPEG2 PS format to burn to DVD-R without recompression. I look for a method which would rearange the blocks into an MPEG stream with correct, DVD compliant, 2048 blocks MPEG2-PS, following the PTS (timestamp) of both the video and audio streams, ready to athor a DVD!

    I found a special version of DVD2AVI called :
    DVD2AVI_PVAView.exe from Michael Ring (http://home.t-online.de/home/michael-ring/) which I have to test with a known bad *.pva capture. But whta to do next to convert to DVD-R without recompression?
     
  4. R.Spark

    R.Spark Guest

    I don't know how to make a DVD-compliant mpeg2 video out of a DVB mpeg2 stream WITHOUT recompression. I don't even know if it's possible... (because bitrate may be wrong, and touching bitrate implies recompressing)
    Personally, I use CCE (Cinema Craft Encoder) and I get good results : I see no difference between the original DVB file and the compressed file.
    c U,
    Robin
     
  5. dirinfo

    dirinfo Guest

    Bitrate of DVB is quite smaller than DVD because of bandwidth price, so that shouldn't be much of a concern.

    Moreover, I suspect that two passes of CCE should take... a certain amount of time, right?

    I can't believe noone has a solution...
     
  6. dRD

    dRD I hate titles Staff Member

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    dirinfo: Sorry for the late reply, but AFAIK, PVAstrumento + DVDPatcher should do the trick for you. And also you can try to repair messed up audio sync with TMPGEnc's MPEG tools (mux & demux again) and some audio tools that allow editing MPEG audio (CoolEdit, AFAIK) -- simply edit the audio by removing or adding few milliseconds to places where you lose the sync and then save this audio again and use it as your audio source.

    Normally losing frames indicates some problems with your capturing ability, particularly with the HDD speed and it should really never happen.

    This might help you as well, one of the many methods avail:

    http://www.dvdrhelp.com/faq#synch
     
  7. shorty2k

    shorty2k Member

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    "Bitrate of DVB is quite smaller than DVD because of bandwidth price"


    hmm... not sure about this, i think the DVB-S/T/C are a lot higher than DVD which maxes out about 9.8, where as DVB is about 20 i may be wrong, i'm sure a read it some where though, please can someone confirm these values?
     
  8. dRD

    dRD I hate titles Staff Member

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    shorty2k: Bitrate depends totally on the stream. DVB-T's total bandwidth is quite small and streams are typically between 1.5 and 3Mbps, while some DVB-S streams are 5-10Mbps. But very rarely larger than that, even that the DVB specs do allow upto 25Mbps if I remember correctly.
     

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