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Old 17 May 2003, 06:09 PM   #1
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Default VBR, audio-video desynchronisation and framerates

Hi Experts out there,

I have been converting movies from Divx3 to divx5 for quite some time (my DVD player only plays divx5, but that's not important now).

Some movies are easy, but sometimes I end up with de-synchronised video and audio streams. I have tried several things, some of which worked for some movies.

Let me tell you what I learned the last couple of months.

Bad frames need to be fixed or masked (I use VirtualDubMod1.4.13, classic or improved scan or both to detect them)

VBR needs to be converted to Wav (eg with Goldwave) and then recompressed with constant bitrate.

Sometimes the video framerate needs to be adjusted to match the audio duration.

I should never use too low bitrates for the audio stream.

These things managed to let me convert 90% of my films, but now I have some movies with VBR sound that won't work. There are no bad frames in it anymore and it plays fine before I do anything. If I then take off the sound with Goldwave or VD, the sound file is a lot shorter than the video file. For a movie I looked at last week, there was a 30seconds difference. Adjusting the framerate did not help.

What do the experts think? Challenging problem?

I hope to read a solution. I have already searched the forum and all I found were the above solutions that did not work.

Kind regards

Peter
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Old 17 May 2003, 07:36 PM   #2
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Just on the odd chance that you're overlooking something:


1) Load the .AVI file into VirtualDub or NanDub

2) From the "File" dropdown menu, select "File Information"

3) Post (here) EVERYTHING you see (both video and audio information), or post a screen capture .jpg of the information box
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Old 17 May 2003, 08:16 PM   #3
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Here is the information. On the left you see the converted file info and on the right the original file info.

Greetins and already thanks for your time.

One more thing i did not mention. If i take the original file, mask the bad frames and convert the framerate such that audio and video duration match, the thing gets out of sync with the VBR.

Regards

Peter
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Old 18 May 2003, 05:40 AM   #4
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1) "VBR needs to be converted to Wav (eg with Goldwave) and then recompressed with constant bitrate."

In the example you've posted, the audiostream has not been converted


2) Does this video use "MP3Pro" audio as opposed to the more conventional "standard" MPEG Layer 3 audio?

3) You might try AVSynch to "cure what ails" this video
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Old 19 May 2003, 05:11 AM   #5
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1) Yes I know that. I did try this and then the desynchronisation starts. That's why I kept the original VBR sound.

2) I have no idea. How can I check this

3) I just tried this and it did not help.

If I extract the audio into a wav file and use this audio with the video there already is a sync problem. If I then adjust the framerate to match the durations (VD) the problem persists.
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Old 19 May 2003, 07:20 AM   #6
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Use AVSync AFTER converting the audio to .WAV format and multiplexing it with a silent version of the .AVI..

Last edited by setarip; 19 May 2003 at 06:35 PM
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Old 19 May 2003, 06:18 PM   #7
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That's exactly what I did. And it did not help. The desync is different but not gone.

This little program looks a lot like the framerate adjuster in VirtualDub itself. Is there a difference?

I already wanted to thank you for your time and effort
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Old 19 May 2003, 06:42 PM   #8
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"This little program looks a lot like the framerate adjuster in VirtualDub itself. Is there a difference?"

Yes. AVSync provides TWO methods of adjusting synchronization (only one of which is similar to that of VirtualDub):

The first (default) is to correct the frame rate. The second is to correct the rate at which the audio track is played.

Sounds like you haven't tried the second method...


"I already wanted to thank you for your time and effort"

My pleasure ;>}
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Old 20 May 2003, 07:34 PM   #9
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I tried the second option as well without success.

What is did is the following; I extracted the audio into a wav file (Goldwave), then merged the extracted audio and a silent video stream (without bad frames). On this big file I worked this program and it changed the audio rate from 44100 to something else, but still the desync persists. If I load this new file then into VD and check for the framerate, it still suggests to change it so audio and video duration match. If I try this, it did not help either.

Is it possible to send you this movie and then you have a try on it?

You can mail me directly at peter.leoni@luc.ac.be

Kind regards

Peter from Belgium
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Old 21 May 2003, 03:51 AM   #10
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"Is it possible to send you this movie and then you have a try on it?"

Sorry, but that's not possible. Perhaps another poster may be willing to help you further...
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Old 21 May 2003, 05:46 PM   #11
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Too bad but I understand.

Can you explain the difference between the two options in the synchronising program, because to me they both have the same result. They check whether the audio and video duration match and adjust one of them. But if one adjustment does not work it is plausible that the other won't work either, or am I wrong?

Kind regards
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Old 21 May 2003, 06:02 PM   #12
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Well, I do have a similar problem like you. But I can solve it by first uncompressed the audio using Uncompressed audio option at Virtual Dub and Direct Stream copy at video option. If after you had uncompressed audio and it was synch with video, then I usually do the video compression to another codec. Then check it up is the audio was match (Usually it will be matched). Then finally recompress the audio section with your prefferred codec. If it make out synch then you must set VBR at your audio.

Hope this can help you.
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