Strange audio sync problem you may not have heard...

[sunnysixkiller]

I am trying to convert to DiVX an mpeg2 file I have recorded on my Radeon AIW 9700, using the default software, i.e. ATI MMC.

I have already edited out the commercials using MPEG2VCR, and when I play the file in any player, such as Windows Media Player, the audio syncs up perfectly.

The problem is however, as soon as I load that file into VirutalDubMpeg2, the sync is all out of whack. Not just a little bit either.

I thought it may have something to do with my commercial edits, but the unedited file causes the same problems as well.

What the problem is:

It is synced at the beginning, but not more than 10 minutes into the movie it is at least 20 seconds behind.

At the end, good god, it must be more than 4 minutes off. I venture to say it may be upwards of 10 minutes, but either way something is very wrong.

I am at a loss to explain what is going on, and I am hoping someone here has had a previous experience with this matter, and may be able to clue me in on what I may be doing wrong.

Thank You in advance for any help you can give.

Craig

[Malevolent]

This thread may or may not provide with some insight, specially the ATI link.

http://forum.doom9.org/showthread.php?s=&threadid=44897

[sunnysixkiller]

Thanks for the reply.

Unfortunatly I can't test any of those theories right now, as I am at work, on a REALLY slow machine. Wow this computer sucks. Try working on a P4 3.06GHz with a gig of Dual Channel DDRRAM @ home with high speed internet, and then come to work and work on a AMD K6 450 with 256 Meg of RAM and dial-up, and it makes you want to kill yourself ;)

But I digress. I think I am going to demux, stretch the audio and remux to see if it cures what ails me.

I will let you all know how it goes.

Thank again guys.

Craig

[sunnysixkiller]

Well stretching wouldn't work, the audio/video was so far out of sync at the end that any stretching caused the audio to become too high pitched.

But you want to know the real kicker?

I am using my AIW 9700Pro to record a TV station. I have tried the local channels, ESPN, MTV, FX, etc. Every mpeg2 recording is out of sync. Each time I have recorded for an hour and when I load it in VdubMod, the audio is WAY behind at the end. By as much as 10 minutes.

Every station except one that is. Whenever I record C-SPAN the audio is always dead on when loaded in Vdubmod, even after a three hour session.

Talk about my own personal hell! The only station that works is C-Span. Argh!

Oh well, if anyone wants some perfect recording from C-Span, I am your man, LOL!

[sunnysixkiller]

Another thing I have noticed is Vdub is reporting a file time of a full 10 minutes less than the file actually is.

Every other program says the file time is 3 hours, but Vdub says 2 Hrs and 50 minutes.

[Asmodian]

Are you sure you are not getting any drop frames? What frame rate is the video and have you tried setting an assumefps in avisynth?

[sunnysixkiller]

The video frame rate is 29.97

[Asmodian]

How many frames are there? How do you load the video, dvd2avi/avisynth or just straight? if you just load it with vdubmod I would definitely try dvd2avi/avisynth and see if that helps. This video slow-down might be caused by dropped frames, the only channel which works is c-span and c-span isn't known for it's action so it should be somewhat less stressful on the ide subsystem if not the rest of the system (though it sounds like you computer should be able to handle it).

maybe you could try assumefps() or convertfps() in avisynth?

[sunnysixkiller]

Thanks!

I loaded it in via AviSynth and all is well. It shows the correct time and the audio is synced all the way through.

Thanks again!

[TerraForce1]

Hi,

if i do get your right (sunnysixkiller) you are recording from a sattelite receiver. If I dont dont read on.

A satellite signal consists MPeg2 stream. And is often called a PVA stream. To get good working MPEG2-streams out of this PVA stream you first have to demux with PVA strumento. After that you can mux the demuxed stream with BBmpeg and you have a valid stream with correct audio and video settings for SVCD or DVD. When converting to another format the sync still will be correct. If not I seriouly will doubt the encoding software you use. I use an ATI all-in-wonder 8500dv who records in Mpeg-2 format. And the way described as above works!