Out of Sync Audio When Appending Clips with VirtualDub

[spinr]

I downloaded a 20 min long AVI video, which the original poster had cut into several short clips of about 3 minutes each. Not sure why other than to shorten individual downloads. The last two clips of the video had the audio out of sync with the video by about 500 ms. I fixed the audio delay with VirtualDub (using how-to article from this forum). I want to reassemble the entire 20 min video into one AVI file. I used VirtualDub's append AVI function to accomplish this, but the audio is out of sync again with the video of the last two original clips that I re-synced the audio to. How can I avoid this happening? Do I need to use another editor to reassemble the clips, or specific settings in VirtualDub that I am not getting correct before the append operation?

[spinr]

Anyone here interested in helping me out??

[DarrellS]

We need more info about the files before we can help like VBR MP3 etc...

As for trying to change the delay of an MP3 file, here is what Avery Lee has to say about the subject. He is the creator of Virtualdub ( Phaeron )

You can't reliably push forward MP3 audio streams in Direct mode. The reason is that the audio format information for an MP3 stream is a bit of a lie -- when VirtualDub thinks it is duplicating the first sample, it's actually adding more sync bytes that are just skipped by the audio decoder. This has to be done either by offsetting dwStart (which VirtualDub doesn't yet support), or by actually encoding new blank frames into the stream.

[Soopafresh]

He didn't cut them on keyframes, probably. You might need to re-encode the thing to keep the A/V sync.

[manono]

...but the audio is out of sync again with the video of the last two original clips that I re-synced the audio to.

You appended using the 2 clips for which you fixed the asynch? So, append with the original still out-of-synch clips. If you no longer have them, if you remember how much you adjusted the delay, make it that way again for just those 2 clips. If you don't know that, throw them out of synch by the same amount your now appended ones are out of synch and then append. If you need instructions on how to find out the amount of asynch, just ask.

[spinr]

Thanks for the suggestions. I gather the problem I have is somewhat complicated. I will try using VirtualDub with the above procedure, but I suspect I need to use an editor like Ulead or Premiere to reassemble the video and reinsert the audio. I have successfully extracted the audio from each clip using VirtualDub. FYI to the the one who asked what encoding, filetype. etc.: video encoding = Divx fastencoder, filetype container = avi, audio = ??? (VirtualDub reports unknown audio encoder). I do have a copy of Gspot, but have not run the clips through it, since I was able to extract the audio streams to WAV files using VirtuaDub. Thanks again to all you who gave suggestions.

[DarrellS]

A GSpot screenshot would help us better help you.

Here is a guide that will help you fix sync problems using Virtualdub and Goldwave.

https://forum.videohelp.com/viewtopic.php?t=300624&highlight=

It was made for VBR MP3 but will work for other out of sync audio.

There used to be a lot of guides for out of sync audio but most of them seem to have disappeared.