Audio drifting out slowly - Gradually goes OOS.

[blackflames]

I am trying to fix an audio stream which drifts out slowly every 300-700 ms or so. I tried 23.976 > 25.000 speedup, but it doesn't work. The source video and the encoded video are both at 29.970, but the audio is slower for the encoded video. I re-encoded the video at 23.976, but still the same. I am pretty sure 25.000 fps won't solve as Vdub shows 24.981 or so to sync the audio and video. I even tried time wrap with video duration/audio duration percentage, but that doesn't help either.

It's in sync for the first 40 seconds or so, but then slowly start delaying.

Video Duration: 4718 s [01:18:38]
Audio Duration: 4725 s [01:18:45]

Ratio: 4718/4725 = 0.99851

Any idea how to use the Vdub's Interleaving per MS/Frame feature to fix this?

[redwudz]

It's probably easier to change the audio length. You could use VD to demux the audio or save it out as a WAV and then use Audacity to adjust the length, then add it back with the video using VD. If needed, you could also adjust the pitch if it's off too far.

That's the method I use most times.

And welcome to our forums.

[blackflames]

Will making the lengths same fix the problem? I tried with some other audio file, but it didn't work. It was in sync in the beginning and the end, but the middle parts were OOS.

[Abas-Avara]

You could try this, I use this for DV captures

Method 1 (after DV AVI capture)
- Open AVI in VirtualDUB
- Go to video - Framerate and then select adjust audio/video framerate
- Save AVI (video: direct stream copy and audio: direct stream copy)

Or try to stretch the audio to the video file. I use Vegas for that

[blackflames]

I already tried the framerate method, but no luck. It says Video is at 23.976 and 23.976 for adjusting as well.

Stretching the audio? I want to shrink it and speed it up, not no idea how to calculate the speed up %.

[Abas-Avara]

I meant shrinking
You can try Syncview to calcute the delay, I did it manualy if it is 300ms late put that number in (if it's late use negative)

Then you can use Hypercube time stretcher (you can use negative numbers for shrinking) I've never try that, Vdub and vegas worked for me.
With Hypercube you can put a time and delay from that moment so far I seen.

Or Vegas go to the end and zoom in to the end and press ctrl+mouse moving to right/left for shrinking or stretching.

[blackflames]

Hypercube time stretcher crashes on loading the AVI and WAV files. How does Vdub work for you? Could you please explain in a bit detailed manner?

[guns1inger]

I am confused by your description of the problem. Are you saying that the audio is drifting in and out of sync across the running the time of the clip, with the sync being out by between 300 and 700 ms each time it drifts ?

Or are you saying it drifts out of sync slowly over the duration of the clip until it is out by somewhere between 300 and 700 ms ?

[Abas-Avara]

Lately I'm capturing VHS tapes trough my camcorder (firewire passtrough), the format is 25.000 FPS PAL
How futher in the video, how more out of sync.
So I load the video file in Vdub and this method

Method 1 (after DV AVI capture)
- Open AVI in VirtualDUB
- Go to video - Framerate and then select adjust audio/video framerate
- Save AVI (video: direct stream copy and audio: direct stream copy)

And it works, I dont know how it does but it does the job.

Here is another method, I dont use it but maybe it works for you if the audio is constant 300ms out of sync

Method 2 (constant audio sync)
- open in Syncview
- look/analyse the sync in ms
- copy the correct ms
- open VirtualDub go to audio-interleaved and under past the positive or negative ms.

If you know exactly the audio sync in ms you can past step 1 to 3

[blackflames]

The step 4 in method 2 is for Preload audio box or the delay audio by a constant ms?

@guns1inger: It gradually gose out of sync. There is a scene where it suddenly delays itself by 10 sec. So I split the video there, sync the beginning and now I trying to sync the rest which goes OOS as the video plays.

EDIT

SyncView gave me fluctuations in the system sync error between -27ms to 10ms. I think I need to make Vdub's Interlaving > preload x ms every x ms or x frames work. Just can't calculate the correct value.

[Abas-Avara]

delay audio by constant ms, if the audio plays 5 sec late constant you use -5sec.

the scene with 10 sec delay, you can split as you say and use this method, later you can make that one video again.

But for the rest if goes slowly out of sync?

[blackflames]

Yes, I did -9800ms constant delay and it's in sync for the first 1 min. Actually the gradual delay is so small initially, it's hard to differentiate until 1 mins x secs as the delay increases.

I had just added "SyncView gave me fluctuations in the system sync error between -27ms to 10ms. I think I need to make Vdub's Interlaving > preload x ms every x ms or x frames work. Just can't calculate the correct value."

[Abas-Avara]

I use Syncview manually, it has a nice slowmotion feature so you can see lips and so see the delay of audio more easily. The automatic sync error don't work on it so far I've expereince with it.

[blackflames]

I have never used it before, so please bear with me. I used examine to play audio and video in slow motion. It pauses after 5 secs and shows -15 to -21 ms as the sync error. I guess, somewhere between is the amount of gradual delay?

Now, let's say a number between 15 and 20 -> 17 is the amount, how do I get "x" in preload every "x" frames?

[Abas-Avara]

Don't look at the sync error, It doesn't give good results (in my experience).

Look in slowmotion and then you have to feel and play with the ms.
Look and exame what you think is right, if you think 3ms late, that fill -3ms and watch again, it's better? > try -4ms.

So bassicly you have to play with the ms and dont look to the sync error

I dont know about preload, I've never used that.




EDIT: What video is it, a TV card capture?
Maybe this would work VirtualDub Sync, it fixes the dropped frames. I've never tried it but the people are positive
It would be easier

[blackflames]

So you mean I note the sync delay every few seconds according to the difference between lip movement and audio playback?

It's actually a dubbed movie. Video is from the DVD5 release, and audio is from from a previous encode with poor video quality. For some weird reason, the encode was at 29.970 with duplicate frames and the audio was in-sync. I tried the new video at both 29.970 and 23.975, but it gradually went OOS in both. Don't how the encoder synced it.

VirtualDub Sync doesn't seem to have any specific or "new" features. How is this better than the VdubMod or the original release?

[Bjs]

This is an actual issue with all versions of virtualdub / mod and the audio will always end up drifting during preview, it is not meant as a video player.

Should the video play in other players without this audio drift then you do not need to correct this but merely correct the audio starting point, either earlier or later.

Syncview (cough) and goldwave can cure issues where audio dose not match the videos time length.

However, if you are indeed dealing with true audio drift then you could use audacity to modify the frequency then use vdub to swap audio for the modified audio.

Have a look at cooledit pro here > https://forum.videohelp.com/topic78178.html

[blackflames]

For the trick with CoolEdit, I have Adobe Auditions. I tried the speed up, but as I don't know the original speed at which the audio is playing. I used the following calculations, but it was now faster than the video:

Step 1: Audio 1 > 4161s x 23.976 = 110723 Frames

Step 2: Audio new > 110723fr / 25.000 = 4428.95 s

Now, 25.000 was just a logical guess, but it didn't work. Any way of computing the precise fps for the step 2?

[blackflames]

WHy does everyone give up helping when it comes to audio syncing?

[Abas-Avara]

I only have a little experience with audio syncing, wich VirtualDub did the job with method 1. And that was a DV PAl 25 fps file.

And one with the exact the same audio file as the DV AVI but with less noise I get that in sync it took 3 days (strechting shrinking cutting etc)

I wish I could help you out

[poisondeathray]

as Vdub shows 24.981 or so to sync the audio and video.

why don't you just change the video fps then? this way you lose no quality. If it's not in sync using that method (assuming the delay offset is zero), you don't have a linear sync problem and it can't be fixed by using simple stretch/shrink methods

if you wanted to re-encode the audio and lose quality, you could do it in audacity too. I think it uses %change, so 1.0 - 0.9985185 = 0.0014815 or 0.14815%

if the audio & video durations now match, and the sync is ok at the beginning, then you have other problems like glitches or desync points, which means you have to process this in segments, or the audio isn't even the proper version (e.g. director's cut or maybe a different scene added etc...)

[lordsmurf]

You're dropping frames.
http://www.digitalfaq.com/guides/video/capture-dropped-frames.htm

[blackflames]

You're dropping frames.
http://www.digitalfaq.com/guides/video/capture-dropped-frames.htm

Other encodes are working fine. I know this can be fixed if I can know the x ms of delay every x number of frames for vDub's Interleaving feature. Trial and error method will take me ages to fix it. Any definite way of computing it?

[ARTO65]

Hey, I know it's a little bit late, but maybe you're still looking for an answer.
You should try Quickstream Fix in Videoredo plus. If not, demux your video with ProjectX.

Let us know if you solved your problem !