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  1. Member
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    Hello,

    I have a method to convert captured media from my PVR and convert to .MKV. The capture is 1080i and I reduce the resolution to 720P so that I get a reduced file size (from approx 9GB down to 4.5GB). As long as I run it through MPEG2 Repair, DGIndex then followed by Delay Cut on the AC3 audio with the Silence option, I end up with a perfectly audio\video synch'd file.

    However, every once in a while I will get a video file that will glitch out of synch anywhere from 2-3 seconds at some point of the converted file. If I note the time on the MKV the out of synch occurs and look at that same spot on the M2TS file through Video Redo I can see that there is some of the audio stream missing. Interesting thing is that if I play the M2TS file you can see a funky glitch but it does not go out of sync, however during the conversion it seems to pick up on it and throw everything off.

    My question is, is there a way to fill this missing audio with silence? Why is it that the transport stream will play fine with the glitch but on conversion it throws everything off?

    The only way I've been fixing it is to re-capture and re-code to MKV, but I thought if I can fix the audio I can just demux the MKV and remux with the adjusted audio.

    THanks for any insight.
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  2. Member yoda313's Avatar
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    I know this isn't a solution just an observation. I am guessing here that what is happening is the source is switching between 5.1 and 2.0 stereo. That is probably what is throwing off the synch.

    If possible try capturing once in 5.1 and then the same source again in 2.0 stereo. See if the glitch is still there in 2.0 only mode. If it is then it this is not the issue. But if the glitch is there in the 5.1 capture but not in the 2.0 capture then the audio is switching in between.
    Donatello - The Shredder? Michelangelo - Maybe all that hardware is for making coleslaw?
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  3. Originally Posted by He11breed
    My question is, is there a way to fill this missing audio with silence?
    So you're saying in those situations where your "usual" method with delaycut fails?

    Not without processing it (ie. re-encoding it) e.g. you can insert silence with an audio editor e.g. audacity , or with avisynth's blankclip() , so that the audio & video durations match to sync up

    Another strategy is to process in segments, cutting the offending error sections out, and resyncing the "good" parts

    Why is it that the transport stream will play fine with the glitch but on conversion it throws everything off?
    Transport streams have timing information , timestamps and recovery information to resync after the "glitch" for playback. When you demultiplex it or use DGIndex, it might not retain that information specfic to the glitch point, depending on the severity of the "glitch"
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    Yoda: There is no audio stream switching, it's either a 5.1 or 2.0 capture (ie. no commercials). thanks.

    PoisonDeathRay: Actually, Delay Cut seems to be working except for this specific glitch. If I don't use Delay Cut with the Silence option what I get is synch at the begining and gradually goes out of synch throughout. Everytime I've had this specific glitch I see missing audio with Video Redo in the problem area.

    I tried Audacity but when I load the AC3 file the loaded file looks to be compressed into a 20 seconds file or something. Playing it is just a bunch of noise.

    THanks for explaining the timing info, makes sense now.
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  5. Try the new audacity beta, you may have to configure ffmpeg in the preferences for under import/export heading

    If you have access to payware editors they can do this too (such as soundforge, audition, soundbooth, goldwave)

    Another method would be to use delay cut to generate your end segments, make a blank audio clip ac3 with the same characteristics (ie. sample rate, channels , DRC, etc....) then join them (either vobmerge or command line dos style)

    copy /b 1.ac3+2.ac3+3.ac3 output.ac3

    Where 2.ac3 is your blank audio
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    Well, I tried the Audacity Beta and I was able to insert silence at the problem area but when I went to save the file, or export to AC3 rather, it wanted to convert the 6 channel AC3 down to 2 channel. Am I doing something wrong or is that the limitation of the software?
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  7. Originally Posted by He11breed
    Well, I tried the Audacity Beta and I was able to insert silence at the problem area but when I went to save the file, or export to AC3 rather, it wanted to convert the 6 channel AC3 down to 2 channel. Am I doing something wrong or is that the limitation of the software?
    You have to set it up in the preferences


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    Boy, totally missed that in the preferences. Exporting now!! THanks!.
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