tmpg dvd author and goldwave to correct a/v sync issues

[kly577]

I have problems with a football game that was taken from VHS. There is a gradual audio/video sync issue. The audio starts off with the video and then gradually gets behind the video when it is played. This happened when the video was encoded to a resolution of 720x480 (it was captured at 480x480). I ran it through virtualdub to apply some filters since the tape was from 1996 and recorded in SLP mode. I then used the framserver to get the audio and video to tmpegenc. I have the files seperated at this point and the following are my details. I am just not sure how to convert the time I see in Tmpg DVD author into the format that I see in Goldwave so that I can correct the a/v sync issue.

Video legnth as reported by tmpg dvd author = 03:05:10;03 (<-----what does this translate into so that I can compare it to the run time of the audio file below?)

Audio legnth as reported by goldwave = 03:05:10.167

Any assistance would be greatly appreciated.

Everyone enjoy their weekend!

[reboot]

03:05:10;03 = 3 hours, 5 minutes, and 10.03 seconds.
In goldwave, check to see that there's no "empty" sound at the beginning. this would probably be a 500ms offset, possibly introduced by virtualdub.

[kly577]

reboot,

Thanks, I thought it was different because of a post I saw somewhere else. There is no dead audio at the beginning in goldwave. I am going to try and timewarp the audio in goldwave to see what I get. Thanks for your help.

[kly577]

Well, no luck. sync is still off. Again a gradual issue. The video is gradually getting ahead of the audio. Anyone have any other suggestions as to how I could get this issue resolved? Any help is much apprecaited.

[reboot]

Sure. If you're ready for it, here's the instructions for progressive sync fixing only.
Some bits may not be specific to the software YOU use, but the principle is the same.

1. The basic principle involved here is to strip out the Audio file (de-mux) then stretch or compress the audio frequency, 48khz, and re-sample to 48khz for DVD. Then convert to *.MP2 or AC3 format and re-multiplex with video stream (only for testing).

2. Demux the MPG file so we can manipulate the Audio file. Run TMPGEnc, click on File and select MPEG Tools. Select Simple De-multiplex tab and for Input, browse to your problem MPG. Video and Audio output names will be automatically generated. The Audio being *.MP2 and video being *.M1V or *.M2V. Click Run and wait until its finished. Exit TMPGEnc.
Alternatively, run virtualdubmod, load your file, select Streams, stream list. Right click on the audio, select Full Processing Mode, then click Save WAV.

3. We now have to estimate the approx time, in seconds, that the audio is out of sync and nearest to the end of the movie as possible. Simply play the original movie with WinDVD or similar player. Windows Media Player is not recommended as it can A/V sync problems of its own. Move slider to near the end of the movie and look for speech, gun fire, explosions, door slamming, etc where you have a precise Audio to Video match up. Estimate the time difference and not the length of the movie. Lets say we find the Audio trails the Video by about 1 second and the movie length was 48 min or 2880 sec (the door slams and about 1 sec later we hear the thud).

3. Run Goldwave and load in the *.MP2 or .wav file. Its also best to turn OFF the Undo feature to speed up the conversions (in Options / File...) Click on Effects and then Playback Rate. We need to change the 48000 Hz to sync the movie, use these formulae:

New Hz (Audio trails Video) = (Movie length in sec + Out of Sync in sec)/(Movie length in sec) * 48000

or

New Hz (Audio precedes Video) = (Movie length in sec - Out of Sync in sec)/(Movie length in sec) * 48000

So for our example, we have:

New Hz = (48x60 + 1) / (43x60) * 48000 = 48115

So change the Rate from 48000 to 48115 (or the number you calculated) and hit OK. Now click Effects again and select Resample. Change the 48115 (or what ever figure you have) back to 48000 and hit OK. Once the conversion is finished, hit Save. For Type select Wave (*.wav) and Attributes as 16bit, Stereo, Signed. Change File name if needed and hit Save. When it finish's answer No and exit the program.

4. We now need to convert our WAV file back to an MP2 or AC3 form. TMPGEnc is the simplest to use for mp2. Run TMPGEnc, and click File, then New Project to clear out old settings. For Stream Type select Audio Only and for Audio Source, browse to our new WAV file and Open it. Rename the Output file name to something different than the original MP2 file. Do NOT change any other settings except Normalize in Setting button (do this only if the audio appears low in volume). Then click OK and finally click Start. When done, exit TMPGEnc. Alternatively, transcode in ffmpeggui to AC3 at 48kHz for your project.

5. Compile the project in DVDLab and test. Alternatively, remux the video and audio in tmpgenc's mpeg tools, simple remux, and select mpeg-2 program VBR. When done, play the new MPG file in WinDVD and check that A/V sync has been fixed. If its still out a bit, you need to start all over again from Point 3 changing the frequency Rate a bit higher or lower. Repeat until its fixed.

If the project is avi, load the video into virtualdubmod, load the fixed .wav as the audio source, and play it to check for sync.
Once you have it, you can then encode the VIDEO ONLY in tmpgenc or other encoder, and transcode audio in ffmpeggui to AC3, then import into DVDLab/TDA.

[kly577]

Thank you for taking so much time to help me out. I will let you know what the result is.

[johns0]

My way of fixing audio that gradually goes out of sync is to load the file into virtualdubmpeg2 and fastforward the file to the end where you see the sound is out of sync,then goto audio/interleaving/audio skew correction and input the value which you think needs adjusting(500ms etc..) and then play the clip near the end and see if the sync is on.

What you can do is keep adjusting the delay till it matches without having to exit out of virtualdub,when you find the right value then extract the wav(dont use the value you found ) and load it into golwave or your fav sound editor and stretch or shrink the audio using the value you found with virtualdub,just add or subtract from the total playing time.

Then convert back to mp2.

[reboot]

johns0 that method works great, if the audio is out by the same amount through the whole clip.
Progressive audio de-sync (wether positive (audio before video) or negative (audio after video)) is completely different.

[johns0]

My method work for progressive,when u add the difference in the stretch mode it changes the whole amount,if the audio is say 50:34 and add 2 seconds it changes the length to 50:36 thus stretching it,it doesnt move the audio 2 seconds ahead.

[ZippyP.]

...when u add the difference in the stretch mode it changes the whole amount,not just a couple seconds.

Right. Vdub-MP2 to find the amount of stretch required then Goldwave and do the "time warp" to stretch it. (I always thought it looked like this guy was doing the the Time Warp. )

[reboot]

OH I get it.
I'm just so used to doing it the other way, but TimeWarp should work as well, providing you know exactly how much to warp it.

[kly577]

You would warp it to match the running time of the video correct?

[reboot]

Theoretically.
You could still have sync issues though.
The audio offset can throw it half a second off, and if there's extra audio in the original, that tails the video, you might have to crop that off.
It's such a simple thing to do in Soundforge, but more difficult switching between vdubmod and goldwave.

[Jeremiah58]

You would warp it to match the running time of the video correct?

If only it would be that easy!
But usually it is not.
You have to notice the ammount of audio delay at the beginning (if any)and at the end of your movie. Then you have to timewarp the audio in order to remove that ammount of progressive audio delay. It is a trial and error procedure, but patiently you could achieve satisfying result.

[rkr1958]

03:05:10;03 = 3 hours, 5 minutes, and 10.03 seconds.

Actually the ;03 indicates 3-frames so if the source video is ~30 fps then the time is 3 hours, 5 minutes and 10.1 seconds.

[rkr1958]

Hey, wait a minute I've seen this post somewhere before:

https://www.videohelp.com/forum/viewtopic.php?p=1268753#1268753

I guess technically this is not a double-post?