[Asterisk-Users] TDM card and voicemail volume

[tmassey at obscorp.com]

asterisk-users-bounces at lists.digium.com wrote on 06/28/2005 07:52:50 AM:

> I was able to raise the volume from inaudible to acceptable by
> increasing the RxGain in zapata.conf by 5db.  I'd rather not go the
> uncomressed wav route, as it will chew up storage in my email system. 

I know I'm way behind on reading this, but I thought I would follow up.

According to this message:

 
http://lists.digium.com/pipermail/asterisk-users/2004-November/072990.html

the reason that uncompressed WAV files are louder is that the software 
that saves the WAV file is amplifying the volume of the files by shifting 
the data two bits to the left (or making it 4x louder).  It is in no way 
"fixing" the underlying problem of the file being too quiet;  it is just 
throwing away dynamic range in order to amplify the file.

Now that may not be a bad solution:  if you don't need the dynamic range, 
but you *do* need the volume, so be it:  you would prefer the off-chance 
of some clipping.  It *has* to be a better solution to using the rxgain 
setting if you don't need to:  rxgain is going to affect echo for the 
worse.  Also notice that the volume of these files is sufficient when they 
are played back over the telephone:  it's only when you play them back via 
a sound card that you have the volume problem.  So, you can't just 
willy-nilly amplify everything.

Hope this helps.

Tim Massey