Sync audio starts-ok but near end 1 sec lag H.264/MPEG-4 AVC AAC LC

[JoeBolden]

mp4 file audio sync problem.
Audio starts in sync but starts to lag and near the end is 1 sec behind.

Is there a way to fix the audio sync without losing quality? Original video source unavailable.`I have a lot of freeware & payware video authoring, conversion & editing software. End result is to create DivX ultra DVD & DVD DL with as little as possible loss in quality.

File Name............ Movie101.mp4
File Size............ 2,249,136,102 bytes

--- Video Information ---
Video Codec Name..... H.264/MPEG-4 AVC
Duration............. 2:34:32
Video Bitrate........ 1772kb/s
Bits / Pixel......... 0.324
Resolution........... 720x304
Aspect Ratio......... 2.368
Frames Per Second.... 25.000

--- Audio Information ---
No of Audio Streams.. 1
Audio Codec.......... mp4a: MPEG-4 AAC LC
Audio Bitrate........ 168kb/s 48000 Hz
Audio Channel Count.. 2

Thank you, Joey

[redwudz]

Your video shows as 2:34:32 long. You don't list your audio length, but it may be 2:34:31 and that may be your sync problem. But you may be able to extract the audio, stretch it by one second and mux it back with the video. That should have no effect on the video itself. If the audio duration isn't the problem, then the video or audio files may be corrupted and harder to fix.

You might drop the file into MediaInfo to see if it shows the audio/video durations.

It also seems to be in PAL format and some conversion at some point may have messed up the sync.

But I haven't worked with editing AAC audio. You might convert it to Divx/MPEG-2, then try to fix the audio. Coverting it to Divx/MPEG-2 will cause quality loss, though. Or someone here may have some better ideas.

[Chrushev]

how do you lengthen the audio by 1 second? I have a similar issue and my video is 2:11:43 while audio is 2:11:42.. i want to try add a second to the audio and see if that fixes my sync issue

[JoeBolden]

Both the video &b Audio show 2h 34mn in MediaInfo

Attached text file shows MediaInfo

movie101.mp4%20mediainfo.txt

[redwudz]

JoeBolden, From the MediaInfo information, I'm not sure what's causing the audio sync problem.

Chrushev, what I have done is, using VirtualDub Mod or the regular VD, I save out the audio with full processing as a WAV, then drop that into Audacity and using the 'Change Tempo' effect, I stretch (Or compress) the audio length to match the video length and save the audio out in the desired audio format. Then I 'Add' that back with the video in VD, deleting the old audio. Then save out the remuxed file using 'Direct stream' copy.

Doesn't always work, but that's one method if the length of the files doesn't match. Both the audio and video need to be compatible with VirtualDub.

But those type of sync errors can be caused by many other reasons, such as bad PAL<>NTSC conversions, corrupted files, bad edits, and several more.

The other type of sync error is a 'offset' error, where the audio and video are the same length and the sync error stays the same throughout the playback. That can be corrected by adding a offset adjustment to change the start time of the audio. VD can do that directly. Or you may have some combination of both types of errors and it can get really complicated.

[Chrushev]

hmm i tried that Redwudz and it s still out of sync... different now but still messed up. and its not consistent, in the begining its almost spot on, by the end its waaay off...

Vobs play just fine though.,.. (from dvd)... i was wondering if there was some program that would server not just video but also audio together frame by frame to replicate the vobs exactly so that everything matches up perfectly.. even if it takes 2 days to go through?

[redwudz]

If the sync loss is gradual, then the length of the video or audio files are likely different. If it goes in and out of sync, or the sync error varies in a non-linear fashion, then the files are really messed up and difficult to fix except by cutting them up and working on each section. But not usually worth the effort.

But if the DVD file is OK, then the program you used to convert is likely the problem. Try AutoGK, FairUse Wizard or one of the other All In One AVI converters. Some DVDs have a short lead in section and if your audio starts there and your program doesn't take that into account, that can cause a sync error. For example if you had a 5 second error and a 5 second lead in file that is missing after conversion, that can explain the error.

With more complex formats like H.264 and AAC audio, I would usually try to convert them to a easier to edit format, then try to correct the sync error. Formats that use variable bitrate on the audio and video both can really be a pain to convert without sync errors unless you use a converter program that can handle it.