Making SVCD from avi with AC3 ACM audio

[sirest]

Well I am not an expert but I can say I do lot of research cause I think the answers are out there. Sofar I have figured things out, but now I am stuck, I have avi file with AC3 ACM audio. I want to make SVCD out of it, but guys who already the answer, you know I get sync problems. Anyway I try to do it, its gonna be problem with audio. I have everything installed. Well ok, now I am doing the final test, to see if it works. I exctracted the audio as ac3 file and I use it as audio source in TMPCEnc. Well my final hope it will be in sync. Trying to convert ac3 to wav file makes it always out of sync. And I (different programs and codecs) get wav audio file always 3 sec. short. So in the end of movie the lips are moving not the same time audio is on. AC3 separate audio file is in sync and I´ll see in 45 minutes if its gonna work in TMPGEnc. Sofar I am looking for advice to solve this problem.

[bugster]

I exctracted the audio as ac3 file and I use it as audio source in TMPCEnc.

Trying to convert ac3 to wav file makes it always out of sync. And I (different programs and codecs) get wav audio file always 3 sec. short.

TmpGenc doesn't tend to like AC3 audio as input. Chances are you will get no audio at all in your SVCD mpeg.


1st, how did you extract the Ac3 audio from the avi, this can have an effect on the results.
Second, If converting it to wav format results in a file shorter than the video, have you tried opening the wav in an audio editor such as GoldWave, and stretching it by 3 seconds?

[sirest]

Well I see your sugestions I guess dont help me. I converted audio as well in VirtualDub and GoldWave and I see I always get in result 3 sec shorter file, so the converting doesnt work, I already hate the process and I dont like the avi files with ac3 audio. But thats my problem. stretching audio in Goldwave in 3 seconds makes it out of sync in beginning of file, cause the sync problem appears after 3/5 of file. And I kind of see the problem but still I dont undestand how to solve it. Still waiting for result i'll get in TMPGEnc now, I know that AC3 is not favorite output for TMPGEnc, but I had to try it myself

[sirest]

well should I give up, I got the result now and its out of sync again. Man I am out of ideas how to have ac3 audio in sync when converting avi to svcd

[mats.hogberg]

Nevermind - thought you where trying to do a AC3 SVCD (which doesn't work...)

/Mats

[mats.hogberg]

My suggestion is to decode AC3 to wav, then using GoldWave Timewarp, stretch it 3 sec, then save as wav. Use stretcged wav as audio source in TMPGEnc.

/Mats

[sirest]

well there's some kind of solution for that as well (ac3 in SVCD - actually some kind of MPEG 6 channel support) but I dont want to go there. I guess I could solve my problem, if I could exctract ac3 audio from avi and convert it to wav with same lenght as the avi file is, but that just about from another world for me now.....

[bugster]

Ok, lets get some more details.

Open your avi file in Gspot, take a screen shot of the window (ALT-PrtScreen) and post that. (You may want to think about masking the filenames )

That will give us a starting point as to where the problems may lie.

[sirest]

Well here you go, I ind of hope you may have ideas ....

[sirest]

OK I will try differently with image, i am not done this here

[sirest]

...

[sirest]

...

[Dilemma]

I used to have the same problem what I did was this....


1.) Saved wave in VirtualDub.

2.) Stopped using TmpGenc. I now use MainConcept Mpeg Encoder (its much faster - real time, and gives excellent quality if you know how to use it). I loaded the video and audio separetly and the sync problems went away! Send me a note if any more questions.

[bugster]

Ok, seen the pic now. One thing I noticed, the source is 25fps - PAL. Are you encoding to a PAL Mpeg?

[sirest]

Yes I know that, I do encode to PAL 25fps, I guess ...I had ideas about that, but I have to double check

[bugster]

Ok, well I see nothing that would suggest any problems. Have you checked the avi for bad frames?

[sirest]

... , yep Idid that, everything is fine, no bad frames ...

[bugster]

Ok, can you describe to me what tools/settings and method you used to extract the audio and convert it to wav? Maybe there is some clue there

[sirest]

Well, I exctracted audio 2 ways, in VirtualDub, audio conversion to 44100Hz and save as wav or in Goldwave opening that avi file or opening ac3 file (which when I extract from video is in perfect lenght and sync) and when converting to wav, the file out of sync again. What I have learned I think before going to encoding process the audio should be in sync already with video .... The issue her is that I get always wav file after half of movie is over out of sync in 3 seconds and if I look the wav file is just about same time shorter then video file. But ac3 audio file is excact same lenght as videfile. I kind a see thats the problem. Well I´ll try the sugestion above now that I am gonna time wrap wav file 3 seconds ....

[bugster]

Something to try. It is possible that this was once two avi's that have been joined together. If this is the case the Ac3 audio stream may have errors in it whic are upsetting the conversion process, so try this.

In virtualdub, open the avi. Then select Audio->Direct stream copy, File->Save wav. This will save out the AC3 audio stream but give it a .wav file extension and also a .wav file header. Change the file extension to .ac3. To fix this, download ac3fix.exe. This is a command line tool. I have no idea if you can use a DOS command line, many can't these days, so bear with me if much of this is obvious. Put ac3fix.exe it in the same directory as your ac3.wav file. Open a command window and CD to that directory. Now type the following command (without the quotes).

"ac3fix file.ac3 file2.ac3"

where file.ac3 is the file you just saved in virtualdub and file2.ac3 is the 'fixed' version output by ac3fix. Hit return and let it run. Now open this file in goldwave and check the length. With any luck it should be correct.
Now convert to wav and resample to 44.1khz.

[sirest]

Well I'll give it a try ....thanks for posting back, I'll let you know how did it go....

[sirest]

Well I did that, when ac3fix was doing is job I got these messages, well about 10 times it said: Current wrongness is - 896 bytes
Checking frame 48913: Wrong frame lenght, expected 87795514, got 1792 (this number was always the same)
and finally Finiched. Found bad frames. Final wrongness is 448 bytes.
Well the new ac3 file turned out fine if I listen to it in MediaPlayer. Excact same lenght as video itself. And the audio is in sync. I made for myself checkpoints what time something should be said in audiofile. OK thats OK. But when I open it in Goldwave I see the audiofile is again 3 seconds short. Well I resampled it anyways and yep its not the lenght I need and it makes it out of sync. Any ideas about all of this ... and why the so called fixed ac3 file is kind of perfect when playing in media player but when I open it in Goldwave it shrinks in lenght 3 seconds ....

[bugster]

Try taking this good Ac3 file and converting it to wav or mp2 using Headac3he.