[asterisk-users] 44Khz files in Asterisk 10

[Lefteris Zafiris]

On Mon, 9 Jan 2012 13:59:07 -0600
"Danny Nicholas" <danny at debsinc.com> wrote:

> Hi gang,
> 
>                 I'm thrilled to be able to use a better quality sound
> in Asterisk 10, but have to change my wav files to sln44 to get the
> benefit. Is there some conf setting I'm missing that would let me
> play a wav at 44 Khz instead of having to do this?
> 
>  
> 
> Sox mon-0a.wav h-1a.wav -t raw -r 44100 jan01.sln44
> 
>  
> 
> Not a biggie if no, since this is a decent work-around.

At the moment format_wav only supports playback of 8 and 16kHz wav
files, so for higher frequencies u have to use the raw slin format.

Just another note, bumbing up the frequency of the sound files doesn't
always means better sound quality. In most cases asterisk will have
to resample the file before playing it back to you which will degrade
the quality. In previous versions of asterisk codec_resample was using
libresample which has very poor quality and introduces clipping and
distortion in the resampled sound. Vesrion 10 has switched to speex
resampler which is fast but not top quality, and its mainly
tested and optimised with voice data so it wont be good to use for
anything else, eg MOH.

The optimal is to match the frequency of the codec you are
using, eg 8kHz or 16kHz for wideband codecs. And if you have to
resample use another resampler like sox (with dithering, lowpass etc)
instead of letting asterisk do this for you.

----------------
Lefteris Zafiris