NO, NO, NO, the sounds could not have been added later. Please take a moment to understand how this tech works.
Glide is a streaming media app. You stream video in real time, like you do with Skype. But's it's using something like Adobe's Media Server (previously FlashCom) to record the video on their servers. It's then saved out to an .H264 encoded file that lives on their servers (not your own phone), and then is available to be shared this way. The file the FBI got was timestamped from Glide's servers and was retrieved from Glide's servers. In other words, although it's possible this recording is of another shooting that happened precisely at the time Brown was being killed, there's no way this audio was created after the fact. Unless you think Glide.com is in on a conspiracy.
Understand now?
I'm not an audio expert, but this guy is: http://www.audioforensicexpert.com/meet-the-experts/meet-ed-primeau/
"I was contacted today by two media outlets regarding an audio recording that was released last night to CNN.
The recording is alledged to be a video chat with the gunshots that killed Michael Brown in the background. I began my forensic investigation by researching the weapon Officer Wilson used to kill Michael Brown. The weapon is a Sig Sauer P229. Next I found a video on YouTube of the Sig Sauer P229 being fired. When conducting forensic comparison, I conclude the weapon in the recording matches the Sig Sauer P229. However, there are other much bigger issues.
Why did this person wait so long to release this recording? You would think he would go to authorities immediately! Next, why did we receive only a portion of an obviously longer recording? Then there is the fact that it sounds like he is reading instead of conversing with his girlfriend like he said he was? Plus, don’t you think he would stop when he hears gunshots? I know I would. Why does he continue to read right through the shots fired?
Seems like a fake recording to me. Something to get attention the day after Michael Brown was laid to rest. Don’t you think the timing is odd for this recording to be released?"
http://www.audioforensicexpert.com/new-recording-michael-brown/
So yes, I'm highly suspicious of it. Even more so now.
ETA: And witnesses have said there was a single shot fired when Brown and Wilson struggled. Why is that not on the recording?
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