Sync issue - how to correct?

[NotSoEasy]

I have a file (XviD) that seems ok in the beggining, but then goes off about 2/3 the way into it all the way to the end.The file uses CBR so not sure how it got out of sync.Here are the stats from Gspot:
AVI File Details
========================================
Filesize.....: 700 MB (or 717,282 KB or 734,496,768 bytes)
Runtime......: 00:57:01 (102,514 fr)
Video Codec..: XviD
Video Bitrate: 1518 kb/s
Audio Codec..: ac3 (0x2000) Dolby Laboratories, Inc
Audio Bitrate: 192 kb/s (96/ch, stereo) CBR
Frame Size...: 624x352 (1.77:1) [=39:22]

I open it with Media Player Classic and while playing, I goto View--->Options--->Filters--->Audio Switcher--->Audio Time Shift(ms)
I then enter 200 , NOT -200 and all is good while I watch.It is pretty much dead on where it should be.

My question is, how can I get this video back in sync? Will I have to re-encode messing with video quality? What tools do I need and how do I do this.Do I need to post any other info on the file?

Thanks in advance!

[Barnabas]

Videos that are out of sync by the same amount throughout the whole files are fixable, but videos that start out in sync and gradually go out of sync as time goes on are generally not fixable. It's usually the result of dropped video frames.

[redwudz]

You can sometimes check for missing frames with VirtualDub. You may have to split the video into parts and fix the sync individually. This works if the sync error doesn't change within those parts as they play. If it gradually drifts off, then you would have to adjust the length of the video or audio. If you have both problems, it may not be worth the effort.

[AlanHK]

You might be able to adjust it with an Avisynth script.

Something like

A=AVISource("video.avi").Trim (0, 50000)
B=AVISource("video.avi").Trim (50001, 102513).DelayAudio(.2)
AlignedSplice(A,B)

Then just play the avs.

[NotSoEasy]

How do I use that and with what? Still new to all this encoding so....

Also, just watch from the start and it goes out of sync at 13:50-13:55 -ish.I cant tell the exact point as this is a concert and that point is the crowd.I know it goes at that point though.The whole thing is 57:00
Not sure if knowing this hepls any, but just in case.

Thanks for the help and replies

[AlanHK]

The idea of my script was to treat the avi as two files, divided by frame numbers, add a delay the the second part, then join them again. Obviously I just guessed the break and delay.
Avisynth is a way to filter Avi video files.
You write a little script as my example, save it as "video.avs". You can load it in most media players, or VirtualDubMod, which will let you edit and rerun it.
It may take you a few hours to get the hang of it, but once you do you'll find it an invaluable tool.
www.Avisynth.org has a directory of Avisynth commands.


Another way would be to demux the avi file, into separate video and audio, then edit the audio, and remux together. The video is unchanged.

Or: try SyncView. I haven't tried it myself but if it does what it claims it might be the easiest way.

[NotSoEasy]

I tried the SyncView and what a pain in the butt that is.To many trial and error steps there.Plus, the entire view has spots of -12 then I get in another place, 9 then back to -10, it's all over the place.Just a bad encode I guess.Was from .ts file and not done good.Sucks because it's a good show.

Thanks for the help anyway.Will have to wait to see if better version comes along.