Audio sync in Virtualdub

[benson881]

Hi I am using FilmMachine & Canopus Procoder to convert an AVI with MP3 to DVD (MPEG2) with AC3 I then multiplex them with TMPGEnc DVD Author.
My question to you all is in VirtualDub it recognises improper VBR audio encoding and from past experience this means once converted it will be out of sync. I know I can uncompress the audio and then convert but i wonder because Filmmachine's BeSweet will create 1 Video file & 1 AC3 audio file when I multiplex them in TDA will they be in sync?

Cheers Jim

[mats.hogberg]

You wont know until you've tried....

/Mats

[benson881]

Thanks

[benson881]

Is there anyone else that has advice on this without me having t take a chance on wasting 15hrs?

Cheers Jim

[thegeeman]

Ask yourself why you are using Virtualdub anyway? You say 'once converted'-to what? Skip V/Dub if you don't need it.
2 options:

1. If you have AC3 plug-in for TDA then it will automatically encode audio to AC3 (2ch) on output-so encode straight into Procoder and author.

2. If not, then demux each stream; convert audio to AC3 (ffmpeggui for example); encode video with procoder and then reauthor with TDA.

Note: TDA will take AC3 2ch and AC3 6ch (it will NOT encode to 6ch though).

[benson881]

I usually use Virtualdub to check if the video and audio are in sync If they are I just go ahead and encode it. If not I convert the audio to wav then encode but I'm sure this will loose quality when I do this. I do have AC3 plugin for TDA but AC3 encoding is already done by Filmmachine. I then add video and audio and mplex.

[thegeeman]

Forgive the stupidity but all i do is scan through my file in approx 5min steps and see if audio is in sync-99 times out of a 100 it works for me!! Too many times as Virtualdub given information that it is out of sync when it is not. What can work ( use that term very loosely with Virtualdub on this next step) is to load avi file-go to 'file', 'File information' and check running times. If do not match, then go 'Video', Direct stream Copy' then back to 'Video', 'Frame Rate' and then check box that says 'Change so video and audio durations match'' then go to 'Save avi'. i've found this to be very hit and miss.

Put a search in for 'Sync' on the left and see what comes up. I use a different encoder and not familiar with Procoder (other than that it takes ageeeeeeeess to encode) so if i do have sync issues, then i just delay the muxing accordingly when setting up and then all is ok.

[benson881]

Cheers mate virtual dub says theres a difference but most do. Gonna try encoding authoring and burning and see what happens will let you know

Cheers again

Jim

[mats.hogberg]

VDub doesn't know if it's in sync or not. It simply can't deal with VBR audio, and tells you so - That VDub will introduce sync problems if you persist in letting it process this file.
When you separate audio from video, if these 2 streams don't "align" at the start (the audio stream may theoretically begin anywhere relative the video stream in an AVI) and then put them back together aligned of course you get sync problems. And if you use tools that don't like VBR audio for processing VBR audio, you're also bound to get sync problems (of a different kind). Your original question can't be answered - it all depends on the source file.

/Mats

[Bjs]

What is the avi video frame rate ???

From what I recall , windows movie maker dose vbr audio .

It might take a while , but you could reprocess the avi in windows movie maker to different outputs , and then extract the audio to wav , and compare it to video length .

It dose work , but as I said it takes time to figure out .