ac3 audio out of sync

[tommcd64]

I have an avi that has 5.1 ac3 audio. In the avi the audio is in perfect sync. I use the vdub mod to demux the ac3. I convert the video to dvd video and then use ac3fix to scan the ac3 file for errors. No errors are found. When I get ready to author the 2 files into a dvd, the audio is out of sync. Any ideas why this is happening or what I can do to fix it?

[SLK001]

Find out what the sync delay is, then use AC3DELAY to add (or subtract) the needed adjustments.

[mikiem]

Back in V/Dub/Mod, if you've got the orig still, file info I think will give you the delay set in the avi. Can as posted add delay, or in DVD authoring prog. specify delay as in V/Dub.

[tommcd64]

I dont' see a way to set the delay in the vdub mod that I am using. I just demux the stream.

[thegeeman]

You say that when you 'get ready' to author, the audio is out of sync!! How did you come to that conclusion? Was it from the files running times? That can sometimes be very misleading-especially with ac3 files. Continue with your method; preview in authoring app (if poss) by playing; if not able to, then ACTUALLY author files-majority of the time there is no problem.

I follow 'almost' the same method as you ( i dont use ac3fix-just drop audio straight into authoring app). I use TDA to author-not sure of your choice. Can't remember last time had a sync problem following this method-don't get me wrong, i do get them but thats occasionally from VBR MP3's.

[tommcd64]

It is out of sync in the preview and when I burn it. If I don't use ac3fix the authoring program doesn't recognize the file. Could there be some header corruption?

[tommcd64]

I am using TDA as well with the ac3 plugin installed.

[thegeeman]

....... When I get ready to author the 2 files into a dvd,....

Are you joining 2 avi's and then demuxing and encoding? Or simply referring to the 2 files as 'audio' and 'video'? Reason i ask is that avi's tend to be about the 700mb mark and with 5.1 AC3 audio-i will assume that that takes up 300mb-400mb on its own!!!

If you are then try demuxing and encoding each file separately. Author together with TDA for seamless playback(Note: DELETE 1st chapter mark on 2nd file!! Sometimes this causes a very slight pause if you don't). TDA will take 5.1 AC3-plug in not necessary.

Can you open the ac3 file with GSpot?

[tommcd64]

The 2 file are audio and video. I demux the ac3 file from the avi and then I encode the avi. I then use tda to author using the encoded video and the demuxed ac3 file.

[Delta2]

is this a 23.976 FPS AVI source ? and you want to convert to DVD PAL 25 FPS ?

well, use Besweet to convert your AC3 audio to MP2 and then remux(join) audio + video

besweet.exe -core( -input C:\DVDTESTE\NOVAPA~1\audio_temp.wav -output C:\DVDTESTE\NOVAPA~1\Encoded_audio.mp2 -logfile C:\DVDTESTE\NOVAPA~1\Logs\Besweet.log ) -ota( -r 23976 25000 ) -ssrc( --rate 48000 ) -mp2enc( -m j -b 192 -e )

[tommcd64]

It is a 23.976 avi and I am leaving the framerate as is. I think there is something in the header. This the only avi I have ever had with the ac3 audio out of sync. It is in perfect sync in the avi it just loses it when I encode it. I will try the ac3delay and see if I can guess how many second of delay there is.

[SLK001]

You'll need to figure out the amount to delay the AC3 audio first. Is it 250msec, 1sec, or 1.5 minutes out of sync?

[mikiem]

"I dont' see a way to set the delay in the vdub mod that I am using. I just demux the stream. "

Prior to demux, file menu -> File information gives figure for audio delay. When muxing, stream list from streams menu, then right click on stream, select interleaving.

At any rate, if delay is listed, try using that figure.

[tommcd64]

It doesn't give any delay listed in the file info. It does say preload 10s. I didn't realize you could set the delay on these streams. I will give that a try.