Audio Sync errors - In trouble again it seems
 

Using Black Prince's wonderful guide, I attempted my first DivX to KVCD conversion today. Because the file is relatively short and I wasn't worried about file size, I used MPEG-2 so I could burn it as an SVCD. However, the audio is slightly out of synch. I went back and re-muxed it, with no difference.

Can somebody help me here? I used Virtual Dub to decompress the wav file and converted the WAV to MP2 using Headac3he, re-sampling the file to 44.1 kHz, TMPGEnc to encode the video, and bbMPEG to mux the two.

Thanks in advance for your help.

You're avi is probably not in a regular framerate (23.97, 25 or 29.97 fps) so the sound goes out of synch.

Encode directly video and audio with tmpgenc, it will give you a perfect mpeg.

Okay hon, thanks so much for the help. I'll give that a shot.

Hugs,

Okay, .avi was at 23.97 but decided to try it anyway. Unfortunately, it didn't work. Other suggestions?

What kind of synch problem it is : a constant one, all along the movie or a sliding one ?

Are you sure the source isn't unsynch itself ?

Okay, I checked the original .avi, and it is in synch. The out-of-synch problem is constant, all along the movie. What I've done to correct it is to add a delay into HeadAC3che when encoding the audio. This has been rather a hit and miss thing, however. I finally, after several attempts, settled on a delay of +200 ms.

However, I'd like to know if I can tell when this extra step is going to be necessary from any of the information given by VirtualDub, and if so, how much of delay will be necessary. Hit and miss for synching the audio doesn't tickle my fancy particularly. :)

The program avi2wav claims to separate the audio exactly as it is in the source, I have never had any problems with it (with VDub neither:) You could try avi2wav or you could try a newer version of VirtualDub.

I'll try it if the problem persists. I've never had a problem with VirtualDub either (until now).

To fix constant audio sync problem do this : download http://www.goldwave.com/release.html

Load Goldwave then Select File->Open to open your video source (Goldwave will ONLY open the audio)

Select Effects->Time Warp

Change %

If NTSC(23,976fps) to PAL(25fps) select 104.27%
If PAL(25fps) to NTSC(23,976) select 95.9%

you can use these % will all film conversions.

Hit OK, your audio should now be either a bit shorter or longer depending what conversion you made.

Select File->Save as

Select File Type, WAV

Select PCM 16 bit stereo

Load this new wav into headache3 and convert as normal.

Remux again.

This will solve constant sync problems throughout the film.

You can use this alternative method:-

Download Beseet and BeSweetGui http://dspguru.notrace.dk/

Load your extracted sound wave from VirtualDub into BeseetGui and then check FRC Presets (on the left) and select the NTSC2PAL (23.976 to 25.000) from the list and covert to mp2.

That is a way far better method than the other one.

My 2 cents.

I think this can also help me with my problem......

I have an .avi with a non standard frame rate (23.979 I believe).

As I use DVD2SVCD this framerate is not supported and is automatically adjusted by DVD2SVCD (adjusted to 23.976 I think).

The problem is that the framerate of the audio is not adjusted because the audio graduately gets out of synch in the resulting KVCD. So I need to adjust the audio of the 23.979 avi to 23.976 manually.

Maybe I can use the "GoldWave" method for this (or better: SoundForge or CoolEdit which I used for my Audio Vinyl conversion projects in the past :-) ).

Any additional info is welcome however...........

Im not that in DVD2SVCD but generally you can fix your nonstandard FPS(23.979) including synced audio by the following:
(As I know its possible to modify the AVS commands within DVD2SVCD so Dialhot maybe can explain you how to integrate it correctly)

Method 1:
Totally in Avisynth.

AssumeFPS(23.976, true)
ResampleAudio(44100)

Method 2:
I did several tests with AVS's Resampling engine and it was ok but not HQ!.
So in case of a wanted high quality I would recommend to use only:

AssumeFPS(23.976, true)

After encoding you open the AVS with the "AssumeFPS(23.976, true)" line in Vdub (watch out for the audio codec of your source !!) and "safe as WAV". Open the Wav in HeadAC3he and use "Convert Samplerate to 44.100!! And encode as mp2.
This will give you a higher quality.

Explanation:
What does "AssumeFPS(23.976, true)"???
The AssumeFPS() Command adjusts the playback speed of your video stream WITHOUT adding or removing frames. And to keep the audio still in sync we use the value "true" within the command which pitches also the "speed" of the audio by modifying the Samplerate of the Audio-component of your AVI. That means therefore the Sampligrate is no longer standard 44.1 khz!!! Maybe 44.098 or 44.105. So the Samplingrate of your audio has to be re-sampled to 44.1khz and there do exist several ways:

1. Doing it in Avisynth by adding "ResampleAudio(44100)" which is ok, but as I said not in HQ!
2. Or without adding "ResampleAudio(44100)" and using HeadAC3he's or Besweet's resampling Engine which got IMHO a better quality. And this will be done by extracting the Audio as WAV before using Vdub, as explained above. This is in my opinion is the right way cause anyway you have to encode your audio in mp2 using for example the Audio converting Apps. as mentioned above.

Thanks for the extensive repy incredible.... :)

I think I'm going for the HeadAC3he option.

Were should I place the "Assume FPS" line in my script ? Just after the source line ?.