[Freeswitch-users] .wav vs .gsm file sizes for recording calls.

Jan Berger jan.berger at video24.no
Sat Jun 25 01:46:00 MSD 2011

Wav is just a standard file format, the size is decided by the contents.

The first format is PCM which is 8000 bytes samples per sec
The second is GSM which is compressed voice - so in short you changed the
file format, but is was and still is GSM inside.

To convert from PCM to GSM you need an application that can do so - WavePad
etc. can be recommended.


-----Original Message-----
From: freeswitch-users-bounces at lists.freeswitch.org
[mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Wes
Sent: 24. juni 2011 23:26
To: FreeSWITCH Users Help
Subject: [Freeswitch-users] .wav vs .gsm file sizes for recording calls.

In my tests, if I record a call in .wav format, a 10 second file is 
about 177,000 bytes, while a 10 second .gsm file is 17,000 bytes.

I  then used sox to convert the .gsm file to a .wav file, and it stayed 
at around 17,000 bytes.  So, is the default recording format for .wav 
using a higher sample rate? vs the default conversion format for the sox 

checking the file type using "file" I see that the larger one is:
RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz

and the wav created by sox via the default conversion from .gsm is:
RIFF (little-endian) data, WAVE audio, GSM 6.10, mono 8000 Hz

So apparently the larger wav file is 16 bit... how are these recording 
parameters controlled?  Can I set it to record directly into the smaller 
wav format? Or will I have to run sox on every file...

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