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I'm crossposting this with reddit (due to extreme desperation). Stackoverflow helped me a bunch in my early Perl days, I'm hoping to have the same luck again.

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I'm cross-posting this in Videostream, as it's my hope that those with more experience with video/audio formats and encoding may have a deeper understand of what may be happening.

Original Post: This will probably be long-winded, so I apologize in advance.

Tuesday we are having a group meeting with our counterparts in the UK (we are in the US). We were told to make a short video to share.

Today I found out that the video files "we" have been sending are missing their audio when they are received in the UK (but the video still plays).

My first thought was "their computer is muted".

My second thought was "bad/missing audio codec on their end".

Since we are so short on time, though, I want to prepare myself for any potential cause for tomorrow (time zone difference causes a delay).

Here's the process that they are currently using:

1) Have file that works (hearsay: groups have sent both m4v and mp4 files, and both "didn't play the sound") 2) Using MS Lync, transfer the file through the instant messenger 3) Once file has been received, audio is missing.

My plans of action:

  1. Use a network drive to store the file instead of transferring it through Lync. Maybe there is an issue with Lync or security software inadvertently modifying the file.

  2. Make sure that they actually have sound (hearsay: they said they do).

  3. Try a variety of different formats. I have used avconv to change my "mp4 (audio stream: aac)" into an "mp4 (audio stream:mp3)", and have also made it into a *.avi (one with aac, one with mp3 audio). I have also WMV version to test, and, for completions sake, a file with a different video stream.

  4. If they still say they are not hearing any audio, have them transfer the same exact file back to me to see if I will still have sound on it after it getting it back.

Now I have not been doing the sending/receiving myself, but here is what I've heard from the person doing it (all hearsay):

  • They are using Win7 and WMP (strict corporate policy on installations, I won't be able to have them use anything other than WMP)
  • Their computers' sound works with other non-transferred files
  • A long time ago, they tried to transfer videos in the opposite direction (UK to US), and when we received them in the US they were also soundless. Their solution at the time was to save the files to a USB drive and have a person bring it over during routine travel.

So that's that. I'm 100% open to any other ideas on what could be causing this, and/or things to test in order to pin down what the issue is.

Thanks!

EDIT: I forgot to mention that I've already tried using Lync to transfer the file from one US computer to a different user's computer here in the US. The file played fine after doing so, audio and everything. I suppose it could still be related to security software they only have in the UK, but, man, I dunno...

TL;DR: Have you ever heard of a video file completely losing its audio stream while its video stream is left intact after being transferred or uploaded/downloaded? Is such a thing even possible?

Tom Light
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  • Have you tried playing it with QuickTime on the receiving machines? It sounds like you are creating the video on iOS devices and then playing them on Windows machines. It may be that the US windows machines have the QuickTime video player but the UK ones don't. – Mick May 07 '15 at 14:02
  • Looks like this was resolved according to the Redit link: "UPDATE: Looks like there was a miscommunication somewhere. I sent them an MP4 and it played fine. So it looks like the issue (may) be limited to M4V files. In which case, I told them to change the extension of M4V into MP4 to see if that restores audio. Hopefully that's the end of this...I'll mark as solved." – Mick Jun 11 '15 at 21:51

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