Merge 2 identical format AVIs, no recompression, audio de-synced on 2nd 1/2

[BilboFett]

When I merge identical format AVIs together, AVI1 + AVI2, making AVI3; both from the same source movie, same fps/resolution/codec/everything, etc. with no new recompression, changes, etc, why would the latter ½’s (what was AVI2’s) audio get out of sync with the video? My drive is not fragmented. It is not a codec issue. The files are uncompressed. I am using virtualdub. I have confirmed that AVI2's audio is in sync before appending it to the end of AVI1.

This is driving me nuts. It doesn't make any sense. Please help!

[setarip_old]

Hi!

As I recall (It's been a few years since I last joined .AVIs), this was pretty much standard fare with VirtualDub. It's easily curable:

Determine how much of "out-of-synch" the second part of the joined .AVI is. Then just load the original second .AVI into VirtualDub (set BOTH "Video" and "Audio" to "Direct Stream Copy") - then, from the "Audio" dropdown menu, select "Interleaving" and enter the appropriate number of milleseconds (either negative or positive) in "Audio skew correction.

Save with a new filename.

Join the original part one to the new part two...

[BilboFett]

If I change the interleaving, and skew the audio... won't it skew it for the entire presentation now... and not just the newly appended "part2" on the tail end? I don't want it to put the audio in the first part out of sync.

[setarip_old]

No, you're not altering the interleaving of the second ORIGINAL at all. (BEFORE joining) Part2.AVI, you are just changing/creating the required audio delay (Positive or Negative) for it BEFORE saving it as a NEW Part2.AVI and joining it to the ORIGINAL Part1.AVI.This in no way affects the playback of the first part of the newly joined .AVI...

[BilboFett]

I set the appropriate audio delay for the new "2nd part", when, played by itself, is delayed and off.... but when merged with "part1"... it sets it correctly!
Awesome.
Good to see you again gunsl1nger :)

[setarip_old]

I'm glad to hear that my instructions worked properly for you ;>}

Who is "gunsl1nger" and what does he/she have to do with this thread, that only you and I have posted to?


BTW - Was the adjustment -1200ms?

[Gren]

i'm having a similar issue w an ac3 soundtrack.

anyone have any bright ideas on how to determine audio skew apart from trial & error?

Edit:

i think it's because when u add the other files, it messes w the audio track AS A WHOLE i.e. it does an unaligned splice rather than an aligned splice on joining. if Vdubmod inserted silence to ensure audio sync, there wouldn't b a problem.

at least that's what i've found w my source