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Audio File Problem

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venom77

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Post Mon Jul 30, 2007 7:45 pm

Audio File Problem

I wasn't sure which category to put this in, but I guess it fits best in forensics.

I have a problem with an audio file, it's a .wav. Our phone system records phone calls "for quality assurance purposes" and are reviewed (or in some cases, investigated) often.

We have a situation where we need to listen to one of these calls and we've downloaded it from the system. It's apx. 2MB in size, but when we try to play it, there is no sound. There are no error messages, and the slider moves across like it is playing the file.

We've tried converting it to mp3, but the 'process' meter goes in a negative direction and never converts the file.

Does anyone know of a good tool that can analyze this file or somehow extract audio out of it?

Thanks.
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slimjim100

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Post Mon Jul 30, 2007 8:48 pm

Re: Audio File Problem

You have to know what codec was used to record the call. Some SIP/VoIP codec's are copyrighted... How did you capture this file and do you have the raw packet dump or it...? if so you can decode it in wireshark as different VoIP codec. I would try RTP 1st to see if that works. Also it could be a 3rd party SIP call that is encrypted.

Brian
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venom77

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Post Mon Jul 30, 2007 11:13 pm

Re: Audio File Problem

Hey Brian, thanks for the reply.

I'm not sure of any special codecs or exactly clear on how the conversations are captured as it's built into the system. I'd have to check with our telecom guy. I do know that we don't normally have problems with listening to these files. And I'm pretty sure that the calls are not encrypted.
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jimbob

Post Tue Jul 31, 2007 8:39 am

Re: Audio File Problem

I used to use a program called Cool Edit many, many years ago. We're talking pre-MP3 here. It was a windows program and could play any number of different WAV formats. You might try that, or maybe something like audacity.

If you've got access to a Linux/Unix system try running file <wav_file> and see if file thinks it's a wave file or not. if it just returns 'data' as a file type it's almost certainly not a plain windows wave file.

Regards,
Jim
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G4Cube

Post Mon Sep 03, 2007 8:00 pm

Re: Audio File Problem

As this recovery and not forensics...
Open a copy of it in a text editor, go here:
http://www.sonicspot.com/guide/wavefiles.html

To help look for what data is incorrect missing in the header.

OR open a copy of it in a sound editor, copy dif' parts of it and paste into a new file to see if you can find good audio.

If that does not work then the corruption may be the whole file, BONK.
Last edited by G4Cube on Tue Sep 04, 2007 10:59 am, edited 1 time in total.

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