audio sync problem, how to work out progressive audio sync delay

[jolt321]

i have a problem with the audio sync on an avi file, ive read through this thread and d/l some of the software, but im not sure how to work out how much of an audio delay to put on mpc.

the file is in sync when i open it any any player on my comp but it gets progressivelly out of sync when i try to play the file through the usb slot on my television, ? anyone got any suggestions?

this is the info i got from media info btw

file size 700mb avi

1 videofile: mpeg 4 visual (x-vid)
1 audio file mpeg audio (mp3)

video stream 1009 kbps at 25 fps

audio stream 128 kbps,48.0 khz, 2 channels,

thanks in advance to anyone who can help me out

[jolt321]

ok ive just looked at another couple of videos that ive watched through the tv and have worked fine with no sync problems, the video framerate for these is 23.997, where as both the ones that dont work are 25.000.

does this mean if i go through mpc and adjust the audio by -1.003 fps then it should be ok???

[jolt321]

ok tried changing framerate to 23.976 using ojosoft video converter and its still not working, audio is still ahead of the video on through my tv

[redwudz]

If the file gets progressively out of sync when playing, an offset is not the cure. That only works for files where the sync error is the same throughout playback.

More likely, you need to adjust the playing time of the audio or the video. The method I use with AVI type files is to save out the audio as a WAV in VirtualDub (Mod) and drop it into Audacity, then use the 'Tempo' effect to stretch or shrink the audio duration to match the video duration. Then 'Add' it back in with the video in VD, delete the old audio, and save both as Direct stream copy. That will mux the new audio with the video. It's fairly fast.

MediaInfo should give you the running times of the audio and the video. I prefer VD Mod for it's audio handling setup.

[jolt321]

solved the problem, all i did in the end was load the video in virtualdub select sync to audio, and direct stream copy in both audio and visual, then selected change framrate so audio and visual match, literally took about 10 seconds. tried it with 2 problem files and they now both work fine on my standalone. much easier than i though it would be. some ppl suggested i had to use a few different programs to do it.
also when i first loaded the problem files in virtual dub noticed the audio was vbr (which must have been the problem ) and suggested i select full processing mode. when i did this it took 45 minutes and turned my 699mb file into a 68 gb monster, which i didnt get at all....???

[filmboss80]

68gb monster? By any chance did you also use Full Processing Mode for the video stream in VirtualDub? Sounds like you re-encoded to uncompressed avi. Only use the full processing mode on the audio stream for changing VBR to CBR. For the video portion, you'd do Direct Stream Copy.

[jolt321]

yea i selected full processing for both.

[plawrence]

Hi everyone.

Just to add a twist to this thread...

I use Ripbot/Anydvd to rip my movies to .mm4 format, then i store them on my dlink 323 nas so that i can stream them via my Playstation 3 (which connects through hdmi/optical on my harmon kardon amp).

Some (not all) movies also have this progressive audio sync issue when i stream them through my ps3. Funny thing is, if i play those same mp4s on my computer using media player, there is no audio sync issue.

given this info, i make the assumption that the mp4 is not the problem. If this is in fact true, i wonder why only some of my mp4s have this issue.

Thanks in advance for any suggestions/assistance.

[freakqnc]

Got the same problem transcoding an FLV to MKV using Handbrake on Mac Pro. The FLV was perfectly in sync, but after processing with handbrake the mkv obtained had the progressive audio sync problem starting from the the 50% of playback reaching an offset of a couple seconds within ~45m playback. At first started as unnoticeable then as noticeable and eventually as plain unwatchable. I wonder if there are any tweaks that could be applied to prevent this issue in handbrake itself. Handbrake is pretty advanced and customizable for a free program, I'd find it odd that something like this would have no fix.

If anyone happens to find out a fix I'd appreciate if you could let us know... obviously I'd do the same if I find a solution/workaround

Cheers!

[davexnet]

Try AVIdemux.

[freakqnc]

Try AVIdemux.

Tried and actually that is not working on the flv file as it crashes AviDemux. Also it seems to have a problem reading the file reporting that it's .H264 encoded and reports various warnings end errors such as:

Codec
Internal error opening CODEC_ID_H264

Crash
Assert failed :0
file /Users/Shared/development/avidemux_related/avidemux_2.5.4/avidemux/ADM_encoder/adm_encConfig.cpp, line 386

Crash
Assert failed :0
file /Users/Shared/development/avidemux_related/avidemux_2.5.4/avidemux/ADM_codecs/ADM_ffmp43.cpp, line 600


At the loading of the file (FLV with .H264 encoded video track) Avidemux warns:

H.264 detected
If the file is using B-frames as reference it can lead to a crash or stuttering.
Avidemux can use another mode which is safe but YOU WILL LOSE FRAME ACCURACY.
Do you want to use that mode?

Giving No/Yes buttons...

Selecting No the new warning is shown that reads:

Index is not up to date
You should use Tool->Rebuild frame. Do it now ?
No/Yes buttons...

Selecting No the video is shown but only about 1/4 (top left) of the complete frame, more or less think about the Dreamworks logo and you can see the kid on the moon and read "DREAMW" where the W appears only for its 1/2 and can see only "V" of it. The video is 576x240 but Avidemux loads it at 320x240 (not scaled but cropped for some reason).

...selecting Yes at the first warning I end up with the same cropped video. I haven't wasted time trying to do a transcoding test. Also there is little info on the app about how to use all the advanced options. Too bad as there seem to be a wealth of them and the app could be kick ass if only wasn't so user-unfriendly and overall buggy.

Thanks anyway for the tip. Avidemux doesn't seem to be very stable nor viable on Macs, perhaps I'll try it on PC and see how that goes.


Cheers!

[davexnet]

Perhaps AVIdemux 2.6? I believe many of the 2.5 errors are resolved. There's a recent build, 7740:
http://avidemux.razorbyte.com.au/

PS 2.5 and 2.6 can be installed at the same time.

[jagabo]

yea i selected full processing for both.

Leave video at Direct Stream Copy if you don't need to recompress the video.

Direct Stream Copy: simply copy the video from the source file to the output file. No decompression or colorspace conversion takes place. This is like taking a VHS tape out of one box and putting it in another. The contents of the tape isn't changed, just the box.

Fast Recompress: decompress the video but leave it in whatever colorspace the codec delivers (no filtering allowed).

Normal Recompress: decompress and convert to RGB, no filtering allowed.

Full Processing: Decompress the video and convert it to RGB, filtering allowed.

With all except for Direct Stream Copy the output will be very large unless you select a compression codec.

VirtualDub's advanced audio filtering has the ability to change the length of the audio, with or without pitch shift. I don't know how well it compares to Audacity's equivalent functions.

[freakqnc]

I long had the same issue and the way I fixed with Avidemux 2.5.4 on Mac OS X 10.6 is to get the details on the source file via MediaInfo. Then I set video settings to copy and select AAC with the same (or closest) settings as seen via MediaInfo. Worked every time so far. The video doesn't get re-encoded (so no loss of quality there nor longer encoding time) while the audio does get encoded and the process keeps the audio in perfect sync from start to end.

I hope that will help anyone with audio sync issues... I tested it with MP4 and MKV containers from FLV sources with H264 video tracks. Haven't done an extremely extensive battery of tests of combinations of source/destination formats so YMMV, but in principle should work well when simply repackaging into another container is the main purpose.

Unfortunately I do have to report the high instability mentioned above where Avidemux keeps crashing...

On some files I keep getting: Crash
Assert failed :0
file /Users/Shared/development/avidemux_related/avidemux_2.5.4/avidemux/ADM_codecs/ADM_ffmp43.cpp, line 600

And there is absolutely no way around it... in those cases only possible thing is to re-encode the full video and keep your fingers crossed.

Note: in case you have to re-encode because Avidemux would keep crashing, do so creating a file with H264 video and AAC audio. Then should the file show out-of-sync audio... try to process as described above (Video set to "Copy" and audio to match the kbps rate and set to AAC)... the audio re-encoding should fix the problem.

Good luck.