Audio video synch

[shashgo]

I have an avi file where the audio and video is out of synch. it starts out with the audio behind the video and then at some point the audio overtakes the video so the movie ends up with the audio ahead of the video. How do I fix this? As far as I know, virtualo dub can be used to fix a steady unchanging rate of desynch (that is the synch is off by the same amount throughout)

[Bjs]

It depend's .

If the audio is constantly out ... from start , then to a specific point ... save that out as a separate part .
Repeat step for end to middle .

The part in the middle can be caused by a number of things .

Adjust the middle component (possibly caused by a joining of clips) using https://www.videohelp.com/tools?tool=SyncView
You need to seperate the video from audio to work with it correctly (vdub can do that) .

You then put that back together on its own using vdub to remux both into a single avi .

Then repeat the steps for both part1 , then part2 in syncview .

Then once there been muxed back as separate parts , you close vdub , reopen it , and append segments in correct order and set video / audio to direct stream copy , and save as a new avi .

Done .

==================

https://forum.videohelp.com/viewtopic.php?t=302152&highlight= for more info

[Barnabas]

You can't really fix this sort of sync problem easily, so don't waste your time.

[redwudz]

That can be a result of the video and audio files being different lengths. This can happen from a bad framerate conversion, such as PAL>NTSC, or sometimes from dropped or missing frames. You can use VirtualDub Mod to save out the audio file as a WAV with full processing or demux it if it's MP3. If it's MP3 VBR, better to save it out as a WAV with full audio processing. I use VD Mod for this as it seems to be easier to work with audio files with it. VD or VDM may be able to show the difference in lengths of the video and audio. Look in 'File>File information'.

Then drop your audio into a audio editor. I use the freeware Audacity. You adjust the audio length to match the video length.

Import the WAV or MP3 to Audacity. (For MP3 output, you need to install the Lame MP3 codec.) Select 'ALL' the audio. Then change the length under 'Change Tempo' in 'Effects' to the length of the video. If you make major changes, you may need to 'Change Pitch' to make it sound right. Save it out as a WAV or MP3, depending on what you want to do with it and check the sync. Then mux it back in with the video with VDM with audio and video set to 'Direct stream copy' and create a new corrected video.

And it also sounds like you may have a offset problem with the audio/video sync. Once you get the length right, you may also have to apply an offset in VDM to get the sync right. But the sync error during the playback should not change after the length conversion.

This can be a lot of work, especially if you have a combination of sync problems. I usually give up if I don't get anywhere in an hour or so.

[shashgo]

It depend's .

If the audio is constantly out ... from start , then to a specific point ... save that out as a separate part .
Repeat step for end to middle .

The part in the middle can be caused by a number of things .

Adjust the middle component (possibly caused by a joining of clips) using https://www.videohelp.com/tools?tool=SyncView
You need to seperate the video from audio to work with it correctly (vdub can do that) .

You then put that back together on its own using vdub to remux both into a single avi .

Then repeat the steps for both part1 , then part2 in syncview .

Then once there been muxed back as separate parts , you close vdub , reopen it , and append segments in correct order and set video / audio to direct stream copy , and save as a new avi .

Done .

==================

https://forum.videohelp.com/viewtopic.php?t=302152&highlight= for more info

I think what Ill have to do is something along the lines of what you said, so I think I need to split the file at each specific point where the audio/video goes out of synch, adjust the sync in each part and then mux everything back together. Then I need to split the combined file again to a size where I can fit it on 1 or 2 CDs.

First I load the file into VDub and under the audio item I set the interleave delay to a number that corrects the synch until a certain point. This I know how to do. How do I split the file at that point so that I can repeat the same procedure on the separated part, and so on until the entire file sections are synched?

Next, how can I combine all the split sections back into one file and then split the resulting file so that it fits on one or two CDs? I have a feeling I can do this part with AutoGK but Im not 100% sure.

[shashgo]

im trying to separate the audio from my avi file using vdub, and i need to use full procesing to save it as a wav file, but when i select full processing and then SAVE TO WAV, I GET A POPUP "No audio decompressor could be found .." How would I know what is required?

Im just trying to synch the audio video portions and im following the tutorial at https://forum.videohelp.com/viewtopic.php?t=307254

please help

[redwudz]

Drop the file into Gspot 2.60 and it should tell you the audio format. I would suspect AC3. For that: AC3 ACM Decompressor. VD should handle MP3 by itself. Ogg is another possibility, but more rare.

[Soopafresh]

If your audio is mp3 - http://www.rarewares.org/files/mp3/lameACM-3.98a11.zip

If your audio is AC3 - http://fcchandler.home.comcast.net/AC3ACM/AC3ACM.zip

[shashgo]

thanks, i was able to separate out the audio from the video (it was AC3 compression). I loaded up both the video and the audio into the sync tool, but I dont know what to do next. The audio video sync is good uptil a certain point after which the video overtakes the audio. Even if I cut up the file, one the pefectly sunced segment and the other the non synced one, I dont know how to use the sync tool to adjust the video audio alignment. The tutorial has something that looks completely different than what I downloaded for the sync tool. Any help?