Audiosynch problem

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Hi,

I am experiencing progressive audio synch problem in NTSC DVD that I've got after converting NTSC AVI file.

The initial frame rate of AVI is 23.976. While converting it with Procoder, I set frame rate for 23.976p ->NTSC (3-2pulldown).

The running time of the AVI file and the resulting m2v has not changed. It is the same.

As Procoder does not work with ac3, I demuxed audio and mutiplexed it back to m2v with TDA.

The initial AVI file has some audio sych but it is not progressive and I easily fixed it. Now it runs perfectly well.

Any ideas would be appreciated. Thank you.

[Soopafresh]

Dropped video frames during encoding perhaps? A/V sync issues should have its own episode of "Unsolved Mysteries"

If you're familiar with the command line, AVImaster is a helpful util to re-index and "fix" your file before encoding. Doesn't ALWAYS work (but what does ?)

You can try something like:

Avimaster.exe -fa input.avi output.avi (fixes audio scale)

or perhaps

Avimaster -sf100M input.avi output.avi (should chop the file in 100MB parts - haven't tried it, though)

You might have to click a few times to get to the author's site

http://www.thozie.de/dnn/LinkClick.aspx?link=AVIMaster.zip&tabid=53&mid=388


ffmpeg as well

ffmpeg.exe -i yourfile.avi -acodec copy -vn -y audio.wav
ffmpeg.exe -i yourfile.avi -vcodec copy -an -y video.avi
ffmpeg.exe -i video.avi -i audio.wav -acodec copy -vcodec copy -vsync output.avi

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If it is about droped fideo frames, is there any solution? May be stretching audio a little if it is possible?

[Soopafresh]

Look above. Added a bit.

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"If you're familiar with the command line" - No. It has been always terra ingongnito for me like DOS. Thanks anyway.

But why are you saying about fixing the AVI before encoding? What's wrong with AVI, which could affect the audio in the resulting m2v?

[Soopafresh]

https://forum.videohelp.com/viewtopic.php?t=316236

Avimux is supposed to be good at sync issues, perhaps you can remux your source file and see if it helps.

http://www.alexander-noe.com/video/amg/

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Thanks for advice about ffmpeg. I'll try this one but still not clear what's wrong with the AVI file.

[Soopafresh]

Look above for Avimux

Remux the file, and tell Avimux to split it every 100MB. Play each resulting piece, looking for sync issues.

Can't tell you for sure what's wrong with your source file. VBR audio is a common cause as well.

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Thank you!

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Hi,

I have put all three initial AVI files (the one I was converting consisted of the three) into AVI-Mux, processed them and I've got one big AVI with no audio problems. The audio synch is OK while when I just joined all the three into one, I had to fix the audio synch (but not progressive).

I demuxed the new audio (ac.3) from the video and tried to join it with the m2v (previous conversion) but I've got audiosynch again.

Am I doing something wrong? Should I convert the video anew? Thanks.

I tried "Remux the file, and tell Avimux to split it every 100MB" but it looks like I cannot do it properly as I do not understand the GUI.

I drag and drop all the three initial AVI files into the upper pan. Then highlight all the three files. I click ""generater source from data files".

Once I get the files in the lower pan, I highlight the audio stream and click "Start". I tried to find the splitting option in the settings but not sure I've found the right one.

Anyway, I cannot see every 100 MB and eventually I get the same AVI consisting of the three AVIs.

P.S. I am not sure whether it is relevant but just incase: the initial AVI files are HD TV rip.

[guns1inger]

So you are joining three parts of an avi file into a single file for conversion ? Slightly vital piece of information, that is.

The general suggestion in these cases is to encode each part separately, and then put them together when you author, or as three titles linked together, or if you use TDA for authoring, by putting all three in the same title and removing the extra chapter points added by TDA at the start of each video. This usually produces a smooth playback with no audio sync problems, although you may get a slight pause between parts depending on how the authoring software handles it.

I have had success with virtualdubmod by first appending all the parts together into a single video, the exporting the entire audio track. I then restart virtualdub, append the parts together again, delete the existing audio and replacing them with the single video track. Save the whole lot out as a new video and test it for sync. If it is good, convert from that.

I have only done this with two part videos, but three should work the same. I also know that many people seem to have issues getting audio sync when appending parts in virtualdubmod, so I may just have had a run of good luck.

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Hi, guns1inger,

Thank you for your involvement.

"I have only done this with two part videos" - With two parts, I did it a few times and it worked every time.


"I have had success with virtualdubmod by first appending all the parts together into a single video, the exporting the entire audio track" - That is exactly what I did: joined all the three together. Demuxed the entire ac.3.

Am I missing something or you misspelled it: "I then restart virtualdub, append the parts together again, delete the existing audio and replacing them with the single video track". I believe you meant "single audio track", right?

Sorry, I also do not get this: "I then restart virtualdub, append the parts together again" But why do you append them again? The video part was not changed after you demuxed the audio or I am again missing something?.

"Save the whole lot out as a new video and test it for sync" - You save in direct video stream, right?

Thank you!

"The general suggestion in these cases is to encode each part separately, and then put them together when you author, or as three titles linked together, or if you use TDA for authoring, by putting all three in the same title and removing the extra chapter points added by TDA at the start of each video" - It is new to me. I will try this if nothing helps as I have already the converted file.

[guns1inger]

All references to virtualdub mean virtualdubmod - trying to type too fast. The sentence in question should read

I then restart virtualdubmod, append the parts together again, delete the existing audio and replacing them with the single audio track

I restart virtualdubmod to clear everything so when I append the videos again, I know there is nothing odd already set. It is basic, healthy paranoia. The videos need to be appended again because virtualdubmod was restarted. Sometimes I find that odd things happen when you are deleting and adding audio. None of it may make any difference, but as this process has so far always worked, I don't want to push my luck

Yes, Direct Stream Copy for both video and audio at this point.

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Got it. Thank you!

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Hi,

I followed the advice to convert the three AVIs (three parts of the movie) separately. The first and the second parts worked just fine but the secon has progressive asynch - the sound lacks slightly behind.

I tried to use GoldWave before trying things that I understand even less than GW but it did not work.

Since the asynch is mild I tried to balance the audio at the beginning of the movie and at its end but it not fine enough.

Can I fix the problem with some not so hard (for me) tools as Soopafresh kindly advised? Thanks!

[guns1inger]

At this point I would be opening my file in an editor, finding the point where the audio sync fails, cutting at that point, and shifting the last section around until it lines up. I would then save this audio track, and use it to replace the broken joined track.

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Thank you, guns1inger.

I will give it a try.