AVI Multiplex question?

[aussiemac]

I have an Xvid which has a 6channel AC3 384kb/sec audio track.
When opened in Gspot...it has the following info

File Length Correct
OpenDML (AVI v2.0)
Interleave: 1 vid frame (42 ms), preload=32
Audio frames: Split across interleaves
Video: 1.00 GB (73.71%)
Audio: 358 MB (25.68%)
AVI Overhead: ~ 3.78 MB (0.36%)

My question... is the way this AVI has been multiplexed not standard ???
particularly when the audio is AC3 6channel??

[FulciLives]

I've always heard that AVIMux GUI is the best program to use for multiplexing an MPEG-4 AVI when you have AC-3 audio.

So you could always dumux and then re-do it using AVIMux GUI if you are afraid that it isn't "proper" the way that it is now.

- John "FulciLives" Coleman

[guns1inger]

What gives you cause for concern ? 6 channel AC3 is perfectly acceptable. Those settings look very similar to videos I have on my HDD at the moment.

[aussiemac]

I have had some trouble with this ac3 audio ...
when converting the Xvid to DVD

The 6ch AC3 audio comes up ....as
being corrupted and not starting with a correct AC3 header ...at
least according to DVD Lab Pro ....
when importing it into the assets area.

Then when DVD lab Pro has finished fixing this problem
and I create/author a DVD from the video and AC3 audio...
the synch is out!!!

So I was going back and looking for reasons why this maybe??
One of them I thought maybe the way this Xvid with 6ch AC3 audio
has been multiplexed.

You are right I have looked thru my own
and found some others with similar characteristics.
But I thought there was a recommended preload of at least 400 -500
mentioned in Xvid guides.....and 96 mentioned for AC3 preload?

Thats why I am asking ....to see if there is any recommended figures
for multiplexing video with audio for Xvids.

Because I was going to then try remultplexing the video and audio together
and see if this fixed the problem.
But this isnt really going to fix the synch issue with making the
Xvid into a DVD.
There just seem to be a lot lately of AC3 audio tracks with this
same corruption ...of incorrect AC3 header.

plus I have spent last hour trying to synch video and audio with
mpeg video wizard...which is good for doing this job!
But I cant get it to synch...its all over the shop ...
ie different at beginning to the middle!!
Its so frustrating ...thats enough ranting

I was looking for any tips or thoughts to solve this issue??

[mats.hogberg]

What if you run the AC3 thru AC3fix?
OTOH, there's always the risk of creating out of sync problems, when you demux audio from video.

/Mats

[aussiemac]

I actually thought the AC3 fix that DVD lab pro uses ..is similar to AC3 fix

[guns1inger]

Delay varies. I have seen short delays and delays in excess of 1100ms. However drifting in and out of sync is usually reserved for variable bitrate MP3 or variable framerate video conversion.

A couple of things to try

1. Demux again with AVIMux GUI and see if the AC3 audio track is better.

2. Convert with ConvertXtoDVD, which will preserve the AC3 audio, and test for sync. If it is, demux the audio from this version and try it in DLP.

[aussiemac]

Thanks gunslinger!!....there is always more than one way to
skin a cat ...or in this case audio

Will give these a try ...and post results. Thanks

[aussiemac]

Using AviDemux certainly seems to be more successful
at getting the audio part...particularly in my case with
this problem Avi with 6ch AC3.

The avi was in two parts ...so I encoded each parts video using FitCD and CCE/avisynth.
Then I demuxed each 6ch ac3 audio part using AviDemux.
Then I synched them using MPEG video wizard and joined the two parts
and output a complete video.
Then dragged into DVDLab pro and authored a DVD.

Another more troublesome Avi I finally had to use ConvertXtoDVD ...and just
a few hours later ...quite a reasonable DVD ready for authoring.
Not as high quality as CCE ...but does the job

Thanks to guns1inger...for your helpful tips!!

From now on ...no more getting the audio using VirtualdubMod...
instead AviDemux is in my conversion process ...and when needed
..ie really troublesome Avi's ...ConvertXtoDVD