[asterisk-users] Preparing music on hold

[Chris Bagnall]

Greetings list,

I've been having a go at preparing some music on hold from CDs clients have supplied, but quality seems really rather poor over compressed channels (tried g729, GSM and Speex). I've been doing the following:

sox -v 0.15 <filename.wav> -t raw -r 8000 -s -w -c 1 <filename.sln> resample -ql

As I understand it, I'm reducing volume to 15% (which sounds about right volume-wise) and downsampling to 8khz, 16-bit mono.

I know MoH over compressed links isn't ideal conditions and is never going to be great, but I should be able to at least make it bearable.

What's the prevailing opinion on using high and low pass filters? One would assume a phone handset is expected to provide frequency response in human speech zones, and not really much outside that (certainly not the 20hz-20khz one might expect of a CD).

Suggestions gratefully appreciated.

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
For full contact details visit http://www.minotaur.it/chris.html
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