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video and sound sync problem

 
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hellboy



Joined: 25 May 2003
Posts: 5

PostPosted: Mon 26 May 2003, 8:07    Post subject: video and sound sync problem Reply with quote

source file: 23.976fps xvid file

1. Used Virtualdub to extract an uncompressed .wav file.

2. Used TMPGenc to convert the 23.976fps xvid file to a 29.97fps m2v file so I can put it to DVD. Thank you very much for your help btw.

Now the problem is that the .wav file is shorter in length than the m2v file.

Was I suppose to find a way to extract audio at 29.97 fps? If so, how? Or should I have converted the video at 23.976fps m2v and then just bring both the audio and video into Sonic DVDiT?
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hellboy



Joined: 25 May 2003
Posts: 5

PostPosted: Mon 26 May 2003, 9:00    Post subject: Reply with quote

Correction to my initial post. I meant to say the video portion of the xvid file was converted at 23.976 fps with a 3:2 pulldown making it 29.97fps which is why I believe the resulting m2v file is slightly larger than the audio .wav file.
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Mon 26 May 2003, 23:15    Post subject: Reply with quote

If the source was 24 fps, there would be some sync issues, but converting a clip from 23.976 fps to 29.97 fps (59.94 fields) should not change its overall length (in seconds).

When you apply 3:2 pulldown, each 4 source frames are mapped to 5 frames in the resulting movie (first frame lasts 3 fields, the second one lasts 2 fields, the third last 3 again, and so on, hence the name "3:2" - sometimes also "2:3"). In other words, if the original had 96 frames (which corresponds to 4 seconds at 23.976 fps), then the new movie should have 120 frames (which corresponds to 4 seconds at 29.97 fps).

So either this conversion is not being done correctly, or it's the audio that's not being processed correctly. Measure the length of the files (in seconds) to determine which one it is. Check:

a) The original movie's length (in seconds)
b) The (extracted) WAV file's length (in seconds)
c) The M2V file's length (in seconds)

RMN
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hellboy



Joined: 25 May 2003
Posts: 5

PostPosted: Wed 28 May 2003, 20:46    Post subject: Reply with quote

So I checked the extracted video and audio files against the original. It's the audio that's out of sync. I tried a couple of things:

1. In TMPGenc, simultaneously converted the video and audio to a m2v and .wav file. Actually turned out worse.

2. In TMPGenc, again converted the video and audio together without the 3:2 pulldown at 29.97 fps even though the source material is 23.976 fps. Got a longer wav file. Still out of sync.

Any ideas?
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RMN
Site Admin


Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Fri 30 May 2003, 21:44    Post subject: Reply with quote

If the problem is the audio, then you can probably fix it quickly and easily with an audio editing program. Simply open the resulting WAV file (or even the original AVI, if you have an audio editing program that can open AVIs), and trim / add silence / retime to match the video.

RMN
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