Gradual loss of sync

[varunb]

I have a tv capture that loses audio sync near the end. Its an avi file. I have tried various methods like goldwave's time-stretching, splitting & merging but not a single one worked. If any1 knows any method that works perfectly for problems like these, then pls let me know. Below is the file information that might prove helpful:

---== Video stream ==---
Source : [Input AVI file]
Description : AVI video stream
Length : 00:43:29.816

---== Other stream ==---
Source : [Input AVI file]
Description : AVI audio stream 1 [tag 0x0055, MPEG-1 Layer 3 (MP3)]
Length : 00:43:29.784

(Audio is VBR MP3)

[tebasuna51]

If the audio sound after the video the problem may be frames missing during capture. The only solution is repeat the capture with other settings (or less busy PC) or be patient and go stretching by zones.

edit: and never use VBR like avi audio.

[varunb]

Well I already know that VBR audio is never meant for Avi. Anyways, isn't there any other way of solving this problem cos another tv capture is just impossible as there won't be any repeat telecasts ?

[unskinnyboy]

This might work. Open the AVI in VirtualDubMoD, go to Video -> Frame Rate. Select the option Change so video and audio durations match, and save as new AVI, with video set to Direct stream copy.

[varunb]

That won't work bcos the current frame rate & Change so video and audio durations match both are same i.e 23.976

[tebasuna51]

Then only you can do is "be patient and go stretching by zones"

[communist]

That won't work bcos the current frame rate & Change so video and audio durations match both are same i.e 23.976
Did you capture it @ 23.976 fps or process it later to this frame rate?

[varunb]

It was captured at 23.976 and tebasuna51, can u pls tell me what 'stretching by zones' means ?

[tebasuna51]

It was captured at 23.976 and tebasuna51, can u pls tell me what 'stretching by zones' means ?

You say: "loses audio sync near the end"
then the first part is ok. Split the audio when begin the async, preserve the first part and try stretch the rest.

Maybe you need more than 2 zones.

[Thunderbolt8]

That won't work bcos the current frame rate & Change so video and audio durations match both are same i.e 23.976
try to use something like 23.9760239 (=25000/1001) fps for the video. it should make the video stream minimal faster=shorter, maybe it'll fit.
just try to experiment with the 23.976 number and try rising the value a little.

[varunb]

I have finally found the solution of my problem guyz. In my case, the audio was 0.310 seconds behind. So what I did was:

1.) demuxed VBR MP3 from the avi using virtualdubmod.
2.) Opened Goldwave, opened the mp3 file -> save as WAV.
3.) Opened WAV file (generated in previous step) -> Effect menu -> Playback rate -> 48003. (cos its 0.3
seconds behind)

4.) Again Effects menu -> Resample -> 48000.
5.) Saved as WAV with different filename(although u can overwrite but one must be sure before
overwriting)

Dats it. The audio is in perfect sync now.

[tebasuna51]

You need add silence (or repeat the last fragment) at this point.

If is an avi, for what TMPGEnc? You never need decompress the video, use always VirtualDub/Mod in 'Direct Stream copy' mode.

[varunb]

What's the need for splitting, adding silence or whatever...when u can just adjust the sample rate & the resample it. Anyways, thanx tebasuna51 for your suggestions.

[tebasuna51]

What's the need for splitting, adding silence or whatever...when u can just adjust the sample rate & the resample it. Anyways, thanx tebasuna51 for your suggestions.
Sorry, I don't see your post edited with the solution to your problem.

I was think the problem is in half of the movie and not progressive.
Then the solution is insert a silence at the cut point :
In Goldwave, instead your steps 3-4), select the point and 'Edit' -> 'Insert Silence' -> 0.31

Your solution is for progressive delay and without preserving the pitch.

In Goldwave you have at 'Effect' -> 'Time Warp' the two solutions for progressive delay:
- Put at 'Length' the desired (actual + 0.310)
- Select 'Rate' for fast, good quality, pitch changed (your method manually make)
- Select 'FFT' for slow process but presserving the pitch

In your case 0.31 sec in 43:29 the pich change is minimal and is better the 'Rate' method

[varunb]

Wait I m getting a bit confused. Can u explain again what I should do after step 2, considering that there's no need to split ?

[tebasuna51]

Wait I m getting a bit confused. Can u explain again what I should do after step 2, considering that there's no need to split ?

Trying to preserve the quality without decode (open in Goldwave is decode mp3 -> wav) and after reencode (wav -> mp3), if you only need add a silence you can split the mp3 (with tools like musiCutter) in mp3_1 and mp3_2, make a silence mp3_s and then rejoin mp3_1 + mp3_s + mp3_2.

The same than insert a silence in Goldwave but without decode-reencode.