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View Full Version : AVI-VBR, or "The odd Couple" again


Quantos
29th September 2005, 03:52
Hello everyone,

this is my first post, nice to be here!


I have several questions regarding the infamous realm of (to be out of-)
a/v-sync problems.

The first task in which I encountered this problem was the editing of an
AVI audio-encoded with a VBR-Mp3 file. Now, I understand that AVI and
VBR-Mp3 are, technically spoken, an odd couple, especially when it comes
to editing/cutting those "creations". I read up some different approaches
to avoid/solve those problems, but I'm still not convinced of which one
is the safest. Those methods are as follows:

1. Using Virtualdub/Mod to save the audio from the AVI as a wav.file,
rejoining the wav-file with the AVI, editing of the file, then reencoding
of the file/s into CBR-Mp3 (again with Virtualdub/Mod). Done.

Now, is it possible to reencode the audio in CBR-Mp3 before the editing or
causes the editing of CBR-Mp3-AVI combinations out of sync problems too?
Second, can I use a common Mp3-Encoder like Lame (with the standard
setup
-parameters from e.g. Hydrogen-Audio) to reencode the audio in CBR,
then just muxing a/v again?

2.The second method of cutting (my files are commercials infested) AVI-VBR
combinations seems to be a modification of Virtualdub, called Vdub-Mp3.

Is this programm really capable to edit VBR "offhand", without further ado?
I read that VirtualdubMod can handle VBR too, but it seems to me that
this feature covers only the conversion of files (in toto), not the cutting or
editing of them in smaller parts or the rearrangement of a scene-sequence.


Well, this is my dilemma, and your help is much appreciated!


Greetings

Quantos

Matthew
29th September 2005, 07:59
I haven't had a need to do this...but my suggestion is: try it. It's pretty obvious if something is out of sync. And you can extract the mp3 and scan it for errors with BeSplit/BeSliced after the fact.

Nandub and VirtualDubMod can both handle vbr mp3.

Like I said I haven't tried it, but I'd think that regardless of the CBR/VBR issue there are potentional sync problems because xdub needs to cut on mp3 frame boundaries, which occur only at 24 millisecond intervals for 48 khz audio. Whether the error would be noticeable is another matter.

kitkatdoom9
30th September 2005, 15:13
I'm still confused. My virtualdubmod does a lousy job with VBR mp3s--lots of skew, and when I set a delay in the stream Interleaving properties, I still can't see how good that guess is, because it doesn't seem to affect the playback at all.

I wanted to crop down a home video my friend sent me (XVID AVI & VBR MP3), and I just can't figure out how to make proper adjustments (and see/hear them! and not have the program crash!) in Virtualdubmod.

unskinnyboy
30th September 2005, 16:02
When you load an mp3 vbr avi into VDM, you will see the following error message:

http://img231.imageshack.us/img231/7528/clipboard012ac.jpg

Hit NO to that, and proceed to edit the avi. There won't be sync issues.

OR

Use Avi-Mux GUI.

Quantos
1st October 2005, 04:01
Use Avi-Mux GUI.

Hi,

unskinnyboy, what exactly do you mean by this. I was always under the impression that AVI-Mux was just a Mux-Demux tool, not a Video-editor.

Greetings

Quantos

unskinnyboy
1st October 2005, 06:23
AVI-Mux GUI can cut avis, join avis, fix A/V sync, extract audio and srt subtitles from an avi and more. And all this it can do for mkv too. More info - http://www-user.tu-chemnitz.de/~noe/Video-Zeug/AVIMux%20GUI/