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Old 4th May 2009, 00:48   #1  |  Link
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[MeGUI] Trying to work out the correct delay for audio for muxing

Hi there, complete novice here, apologies! (I have trawled through the forum for an answer)

I am encoding x264/AAC in MKV container using MeGUI. I am currently encoding the film Aliens (PAL) but am having audio sync problems after muxing video and audio. Process goes like this:

System is XP CPU is Core 2 Duo. MeGUI is fully up to date.

1. Extract .vob with DVDdecrypter (audio is in sync in resulting .vob file)
2. MeGUI, Create D2V, selecting 6ch audio (no delay tagged in AC3 file)
3. Create AVS script (source is PAL, auto crop, resize suggested mod 16)
4. Encode video in x264 (double checked frame rate is 25fps) with HQ Slow x264 profile @ 650 kbit/s
5. Encode AC3 audio with BeLight/BeSweet to AAC HE normal quality VB mode
6. Mux audio and video. Resulting audio is not in sync in .mkv file (several hundred milliseconds approx)

According to Mediainfo the video and audio are the same length.

I have also used Auto GK in the past to create an XviD of this film and had the exact same audio issue? (used DVDdecrypter to rip vob that time also)

I have tried splitting the .vob by cell ID. When I create a D2V file from a random cell the resulting AC3 audio file is tagged with a delay (anywhere from 100-300ms) If I then encode this then Mux (delaying the audio by said amount) the .mkv in sync.

So my problem is how do I determine the correct delay for the whole movie if the delay varies so much scene to scene?

I have encoded several films using this method with no problems with audio up until now. Any help greatly appreciated.

Last edited by s162000; 4th May 2009 at 00:55.
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Old 4th May 2009, 12:41   #2  |  Link
tebasuna51's Avatar
Join Date: Feb 2005
Location: Spain
Posts: 6,914
Maybe you need read the 'Analyze Sync' in the DGIndexManual.html located in your ...\megui\tools\dgindex folder.
BeHappy, AviSynth audio transcoder.
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Old 4th May 2009, 17:26   #3  |  Link
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Thanks for the reply Using Analyze Sync there appears to be no 'fishy' audio delay at the beginning of the stream. However there are several 'fishy' delays of several thousand ms dotted throughout the stream. Apart from these, the delays in general go from +8 to -130 ms throughout the stream.

By chance I came across this thread where another more experienced member has recently the same problem. Is it just a case of trial and error to work out an acceptable/compromise delay and leaving it at that?

Last edited by s162000; 4th May 2009 at 17:50.
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