Problem with Append AVI in VirtualDub - Audio of Sync - How Fix?

[Chakra]

Help please with the following problem.

I downloaded a series of avi files. For some of those files there was a series of 'fixes'. The fixes were there because some of the main files were missing the last few minutes of the video. I tried to appended the fixes to the main files. This was not possible as the following was the case:

1. The main files and the fixes had different frame sizes.
2. The main files and the fixes had varying bitrates for the audio stream.

I did the following:

1. Saved out the audio as 'wav' files and then had them re-processed back into the avi's, all that the same bitrates all AC3 audio.
2. I resized all of the main files and all of the fixes to the same frame size.

I checked each separate file - main and fix - for audio syncronisation, they were fine.

I then appended to each of the main files the fix that was appropriate to it and saved off the (new) main avi.

However, when I playback the new files I find that the audio for the part of the avi that used to be the 'fix file' is now way out of sync with the video (the earlier 'main file part' still plays fine).

I don't know how to proceded from there. Any suggestions how to deal with this in VirtualDub (also have VirtualDub Mod and NanDub) would be appreciated?

P.S. I'm relatively new to this kind of thing so please pitch responses at a level that a newbie can understand.

[poisondeathray]

1) Is the "fix" complete with video and audio (i.e. just the last few minutes?) Is it in sync? What is the fps for the video (for both main and fix segments)?

2) Does the "fix" overlap with the old main section? or are the ends "perfect"? for both audio & video?

3) Does the duration match? for audio & video of both main and "fix" sections both before and after processing?

You can use mediainfo to check these running times & info

You might also give avidemux a shot for appending main+fix segments, it works similar to vdub, but I find it handles some things better.

[manono]

When both files are in-synch by themselves but the second one goes out-of-synch after being joined, it means the audio for the first one is shorter than its video, and when the second one is joined to it, its audio "slides" up against the audio of the first one, throwing the former second one out of synch. The fix is to find out the amount it's out-of-synch after being joined (I use MPC for the job), and then delay the second one by the same amount. That is, if after being joined the second part needs a 500ms delay to be in synch, take the second part before being joined and apply a 500ms delay. By itself it'll be out of synch by 500ms, but after being joined the whole joined AVI will be in-synch. Or should be. I think.

[Chakra]

Many thanks to you both for the replies.

Yes the audio was in sync in both of the separate files I refered to as 'main' and 'fix'. Only the 'fix' part was really way out of sync once it was appended to the 'main' and the new single file saved off.

As giving avidemux a whirl seemed like the easy way out, if it worked, I tried that.

Didn't know what it meant but it asked if I wanted to unpack packed 'bitstreams'. I said yes and it appended the fix files fine and with audio in sync in the final 'full' file, so problem solved.

I tried again without unpacking the 'bitstreams' and it still worked fine (so none the wiser over bitstreams).

In any case, I've got a fix, a couple of new tools and an idea to put on the backburner for an occasion I hope never arises.

Well done and many thanks again.