AVI gradual loss of sync

[mathieumg]

Hope I'm in the right forum...

I used my Sony video camera to film a short movie (lasting below 20 minutes) and I used the USB (2.0) port to import it in .avi using their software. That import software creates a new .avi every 10 minutes of video, so now I have a 3.89 GB .avi and a 2.64 GB one. The problem is that in both of these .avi there is a gradual loss of synchronisation. At the beginning they are synchronous but the slowly desync and at the end I get a 2 seconds gap with no sound.

I thought this would have been the solution: https://www.videohelp.com/forum/userguides/140540.php but it is for Mpegs...

I also tried that: https://www.videohelp.com/forum/userguides/142555.php but it said my video had no bad frames...

So now I'm asking for your help, how can I resync my video, in .avi format?

Thanks a lot in advance!

[redwudz]

If your camcorder has Firewire output, use that instead of USB. You will get much better quality. Firewire cards are cheap if you don't have one.

But for your sync problem, the first guide you linked to will work fine for AVIs, including DV. Read down a little on the first page and it mentions that.

The usual problem with your type of sync loss is the audio and the video are different lengths. If you make them both the same and you have to breaks in the sync or video, it should be easy to adjust.

[mathieumg]

2. Use TMPGenc and under MPEG Tools to demultiplex the MPEG file into two separate files. So in this case it would Let It Be.m1v for the video and Let It Be.mp2

I don't think that would work for an .avi, must I convert my files to MPEG?

About the FireWire, I don't have a card, nor the money for it. But I plan to buy a SoundBlaster Audigy someday, which also has a FireWire port...

[redwudz]

For step 2, just use VirtualDub and either demux or save out the audio as a WAV. I don't use Sound Forge, but I'm sure it will accept WAV sound. Then after you make your adjustments, use that file and either mux it back with the video in VirtualDub, or if you are encoding to MPEG, use that adjusted sound as your audio source in the encoder, along with the original video.

I rarely have DV sync problems, as I use Firewire for the transfers. You can have them with Firewire if your system drops frames, but that hasn't happened. Firewire cards are a lot cheaper than your Audigy card. I got a PCI one a couple of weeks ago for $13US.

[mathieumg]

and either demux or save out the audio as a WAV

What is mux/demux, and how I do it in VirtualDub?


For the camera, it belongs to a friend and it is for a school project so I'd only use that firewire port rarely, so having it on the Audigy is more like a "bonus" for the day I'll buy it

Thanks again

[redwudz]

Demux=Demultiplex: Separate the video from the audio. Usually generates two files.

VD doesn't give you two streams, just separates out the audio. Save as a WAV is what I usually do. But if you want the audio in the original format, you can demux. I use VDMod and under 'Streams', 'Stream List' you will see 'Demux' near the bottom. AFAIK, DV audio is WAV anyway, so either way you should get the same thing. I don't think the regular VD has the Demux option, at least I haven't seen it, but it will save as WAV.

There are also two programs in tools to correct sync problems. I haven't had much luck with either, but SyncView and Hypercube Time Stretcher may be worth a try if you are not getting anywhere.

I understand why you don't need a Firewire card at present. I'm not sure of USB transfer quality. That's normally used for low resolution video to send over the web or still pictures. You may have been better off to do a regular capture with the composite output of the camera. But, if you don't have a capture card, that would not work.

This is probably ending up to be more work than you anticipated, but it will be a learning experience. 8)

[mathieumg]

Thanks for all the tips, will give it a try once I get free time this week ^^

If you mouse-over the button "Computer Details" above my post, you see that I do have an All-In-Wonder .

When I was making videos with my own camera (old 1995 thingie, bleh :/) I was using the composite entries on my capture card to import it, as it was the only solution (but I was getting desynched mpegs as well haha).

When I saw that my friend's camera, which is indeed more recent than mine, had usb/firewire I tought I could try USB in case it gives better video quality (which is true) and no desync (which is false ) compared to my capture card

That's my long story lol.

Will give feedback once I tried your solution, thanks again!

[Paul Glagla]

There is a simple solution which works in some cases. Because progressive out of sync in AVI is often due to a bad framerate of the video part. So I suggest this simple method:

1) open the avi file with DVdate

2) look if the video duration is different of the audio duration: if they are different, the audio duration is given in parenthesis after the video duration. If they are not different, the method is not appropriate.

3) use the command "Change the frame rate" in the menu Video of DVdate (or type CTRL+Y). Try to set a frequency so that the two durations will be the same (some experimentation is necessary, or if you are good in calculus...). This will change the video framerate, but keeps the audio framerate constant.

Try then to see if the issue is fixed.

[mathieumg]

OMG! Really great piece of software. Saved me hours of hassle and re-encoding etc. Modified directly the file (even though it was ~4GB big) and worked at the first try, no lag!

Merci beaucoup beaucoup Paul