Synched .mov file become un-synched after upload?

[ExileFilms]

Every week we submit .mov files to a client via upload to their server. Recently they have complained that the audio is out of synch. We test final .mov file on our system and everything is perfect. Cannot figure out what the problem is.

[Baldrick]

Just a file data upload? Not to any video site like youtube, vimeo etc?

[AlanHK]

Every week we submit .mov files to a client via upload to their server. Recently they have complained that the audio is out of synch. We test final .mov file on our system and everything is perfect. Cannot figure out what the problem is.

First make sure that you're both using the same software to play it.

Preferably something self contained that doesn't rely on system codecs.

For high resolution files if your system isn't powerful enough it might lag.

[ExileFilms]

Thanks Alan for your assistance. One thing I forgot to mention that may be an issue. We send our audio file to a professional sound guy for sweetening. He sends it back and we re-synch it. The client called today to clarify that the synching issue does not happen all the way through, just some spots where it is off by about 2-3 frames. Do you think it is our sound technicians fault?

[AlanHK]

I hope that you aren't using a VBR audio format at any stage.
That can cause sync problems.

Also I don't know why you'd need to resync the audio.
The processing should not change the sync at all.
Your sound technical should know what he's doing and why, ask him.

[ExileFilms]

Thanks again Allen, I will inquire and post when I find out. You're awesome!

[ExileFilms]

This was the sound editors response: Most of my sweetening is done with EQ, stereo expanders, and compressors.

[Cornucopia]

Which means, unless he/she changed the sample rate or something, or used VBR compressed audio, the file should have the same sync as the original!

Scott

[AlanHK]

This was the sound editors response: Most of my sweetening is done with EQ, stereo expanders, and compressors.

So you've told him about the sync problem?
He has the files the expertise and he should be able to work out what your problem is better than us who are just guessing.
But don't piss him off with accusations.

It's very easy to lay the original and the new soundtracks next to each other in an audio editor and visually confirm that sync has not changed.

[ExileFilms]

I appreciate everyone's feedback. This week, after shooting, we are doing all the post work at their location to see what's going on.