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AVI synch is perfect, outputted m2v and ac3 are off

 
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trimipi



Joined: 03 Sep 2003
Posts: 9

PostPosted: Wed 3 Sep 2003, 16:17    Post subject: AVI synch is perfect, outputted m2v and ac3 are off Reply with quote

One more qyestion. I have exported an AVI from Premiere 6.0. It looks and sounds perfect. I am encoding the video to m2v using TMPGenc and the audio to AC3 using BeSweet. I've multiplexed the two files with both TMPGenc and BBMPEG, and the audio ends up a few frames out of synch.

I've been tinkering with splitting the audio with both VirtualDub and Premiere. Both yielded similar (out-of-synch) results. I also tried not converting to AC3, and just multiplexing with the wav file. This didn't work either.

Has anyone else experienced this problem?
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RMN
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Joined: 04 Feb 2003
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Location: Lisboa, Portugal

PostPosted: Fri 5 Sep 2003, 13:37    Post subject: Reply with quote

I find it a bit unlikely that you've multiplexed a MPEG-2 video file with an AC3 audio track using TMPGEnc. MPEG system (audio+video) streams can only have MPEG audio, not AC3.

Or are you talking about TMPGEnc's authoring program ("DVD Author")?

The only format where you can have MPEG-2 video with AC3 audio is the VOB format used by DVDs.

In other words, the multiplexing must be done by an authoring program, and not by a MPEG encoder.

RMN
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trimipi



Joined: 03 Sep 2003
Posts: 9

PostPosted: Fri 5 Sep 2003, 16:20    Post subject: rmn Reply with quote

With all due respect, I have multiplexed with AC3 using TMPGEnc's mpeg tools (not their authoring program). Go ahead and try. It works just fine.

Any idea why the audio would be out of synch?
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RMN
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Location: Lisboa, Portugal

PostPosted: Fri 5 Sep 2003, 17:51    Post subject: Reply with quote

It might work just fine, but it's not a valid MPEG-2 system stream. At best, you could hope to create a valid VOB file, but I think TMPGEnc doesn't understand AC3 files very well. It's probably interpreting the AC3 file's header as part of the audio, and this is causing the loss of sync.

If you have a MPEG-2 file and an AC3 file, simply load them both into your authoring program and link them together. The authoring program should be able to create the VOB files correctly.

RMN
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Last edited by RMN on Fri 5 Sep 2003, 18:03; edited 2 times in total
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trimipi



Joined: 03 Sep 2003
Posts: 9

PostPosted: Fri 5 Sep 2003, 17:58    Post subject: Thanks Reply with quote

I already tried that using TMPGEnc's authoring program. I had the same synch problems. I guess I'll have to keep experimenting. Sigh... Sad
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RMN
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PostPosted: Fri 5 Sep 2003, 18:04    Post subject: Reply with quote

Then the problem is probably in the files themselves. Are they exactly the same length?

RMN
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trimipi



Joined: 03 Sep 2003
Posts: 9

PostPosted: Fri 5 Sep 2003, 18:25    Post subject: yes Reply with quote

Absolutely. I tried frameserving last night, and I haven't had a chance to synch everything up. I'll do that tonight and see if the problem goes away.

Strange though, isn't it? It synchs fine going in, the two files are the same length coming out, but they aren't in perfect synch anymore. (It's only a few frames, but that's enough to look "off".)
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