Help Needed converting AVI to MPEG2

[Stavros]

I am hoping somebody will be able to help me with a problem I have been having for some time, before I give up with DVD all together.

I have been trying to convert several DIVX files to MPEG2 for four or five months now with no luck. The main problem I have encountered is that when I try to convert the file from 44100Hz to 48000Hz the audio goes out of sync. I have tried to conert both directly with TMPGENC and by converting the Hz first with Virtual Dub and recived the same result.

I followed the guides and saved the audio first as a WAV file in Vitrtual Dub before encoding in TMPGENC which did improve the video but did not fix it.

If I then author and burn it uisng DVD-lab the file just gets worse.

The first file I converted to DVD was the only one that was perfect. I am now starting to loose faith with the whole process and am even starting to doubt that file was in sync.

The other thing that confuses me is the differences between the audio and video length. With every video file I have ever had the two have been different. I have two files where both are out exactly the same but one is in sync and one isn't.

Does this happen the majority of the time or have I just been unlucky.

Any help or advice would be hugely appreciated.

[Poplar]

Don't give up yet, pal. I would like to know more detail on your source, such as codec, frame rate, audio format, duration, etc.

But I assume it's of Divx varieties with mp3 audio. This is where the problem comes in. According to some documents I read, FhG MP3 codec was a little lazy in reading samples, which will result in loss of play time and a/v synch. Another problem is how to adjust A/V delay. You don't have any info on A/V delay from AVI files and you bascially have to guess and estimate it by trial and error when multiplexing MPEG2.

My advice is, get a decent audio editor, resample and adjust duration if needed. Estimate A/V delay and multiplex video and audio. Most of times, it will fix the problem.....

[SaSi]

First of all, don't loose faith. To give you some hindsight, once you master how to do things and solve all the problems, you'll get bored and drop the hobby for another challenge. So hope that problems keep coming...

Now, on the problem,

I don't download and encode video. I was only once given from a friend a 1 hour video compressed with DivX and VBR Audio to make into DVD, and I had exactly the same problems with you.

What I've learned is that the most common cause for such de-sync between audio and video is using VBR MPEG audio compression in the AVI file. It appears that VBR MP3 audio with DivX video, although perfectly valid for AVI, are not a good source for Tmpgenc or other encoders.

First of all, the good step you did was to extract the audio into uncompressed WAV. (Was it uncompressed? - If not, try again).

A second thing to check is the DivX codec. The newest versions, 5.05 are a mess, at least when it comes to them being the source for MPEG encoding.

It's best not to use the DivX directly as a source to Tmpgenc. MainConcept is better in handling DivX. Try it, the demo version is free and although it embeds a watermark, it's fine for testing sync. It's also faster than Tmpgenc.

Whatever encoder you choose, I suggest that you convert the DivX file into a hufyuv compressed AVI (with audio still separate as wav). The hufyuv codec (can be found at the tools section) is free and although people don't like it because it doesn't compress too much (it's lossless) it has the virtue of generating complete frames (no predicted frames here). My guess is that this helps the encoder keep the timing better than DivX.

So, in summary, the simple steps are:
1. Download and install hufyuv
2. Use VirtualDUB to save the video as AVI compressed with Hufyuv and audio as uncompressed AVI
3. Use Tmpgenc (or try Mainconcept ) to encode the two separate sources.

Let us know how it goes.

[Stavros]

Thanks for the advice.

The video was originally 24.999FPS but I converted it to 25 FPS. Once I had done this the length of the video and audio matched.

They are 00:50:58 in length.

It has been compressed using DixX 4.

The audio bitrate is 64kbs DivX (smae as WMA)


The other files were all already 25FPS but the video and audio ran at different lengths. Apart from that the other files are the same as the first one.

Poplar,

I'm not sure if adjusting the audio will work because it runs in and out of sync more at different parts of the video. (rather than moving further out the longer the video runs.) I would however really appretiate some detailed advice on how to do this so I can give it a try.

If the problem is that the video and audio lengths are different why is it that video files that are near enougth the same length and are also exactly the same when it comes to the differnces in length between audio and video can be different when it comes to the audio sync? (or is that just my imagination?).


SaSi,

The DivX codec I have installed is the new one.

What is hufyuv and will it still have the same effect when the file is already been compressed using DivX.

Thanks again for the help.

[Stavros]

After further investigation it turns out that the audio is changing length when I save it as a wav file in full processing mode whether I convert the Hz or not.

Does anybody know why this could be happening?

Again, any advice would be greatly appretiated.

[Stavros]

I have worked out how to stretch the audio from the AVI to match the video length. I then encoded the the audio and video in TMPGENC. Although this did greatly improve the quality of the video, the audio shortened very slightly.

Is there any way of stretching the audio after the file has been converted to MPEG2?

[Stavros]

With the advice I received about stretching the audio I think I have got as close as I am going to get to the video being in sync.

I have now burnt it to a disk using MF2.

The only real problem I have left is playing the DVD in my standalone DVD player. The DVD plays fine on my computer but as soon as I play it in my standalone it goes completely out of sync.

Somebody please help[/b]