Summary:ASTERISK-13053: default sound files for Core Sound and Music On Hold File Packages not the same format
Reporter:Paul Belanger (pabelanger)Labels:
Date Opened:2008-11-12 01:36:25.000-0600Date Closed:2011-06-07 14:10:07
Versions:Frequency of
Description:By default the sound files get installed as:


We should set the same default format system wide.
Comments:By: David Woolley (davidw) 2008-11-12 04:57:10.000-0600

GSM is a vocoder type codec, which means it it not really good for music.  Using a common format, that was also appropriate for music, would force you to use uncompressed voice files.

By: Paul Belanger (pabelanger) 2008-11-12 08:28:33.000-0600

davidw: And using uncompressed voice files is good or bad?  Sorry for my lack of knowledge.  Usually when we install asterisk we will make sure our sound files are the same format as the codec (majority of the callers use).  This way to save CPU resources on transcoding.

By: David Woolley (davidw) 2008-11-12 08:38:31.000-0600

Sending music to GSM phones is bad, or at least you need music that is designed to be sufficiently voice like that it is not badly distorted.

Typicaly you want uncompressed voice files (in the largest format you can spare room for) if you use any uncompressed codec, plus one set of voice files for each compressed codec that you use.  That's because converting between uncompressed formats is cheap, but converting to or between compressed ones is expensive, and you will get losses on both sides of the conversion, if you convert between compressed formats.

By: Paul Belanger (pabelanger) 2008-11-12 08:55:01.000-0600

So I guess it comes down to 'spare room' (HDD space and bandwidth) vs CPU resources for the sound files?  Since there is sound issues for MOH and GSM, we could move the core sound files to WAV for the default install.

By: Matt Riddell (zx81) 2008-11-12 17:33:42.000-0600

The core sound files are voice, so they are not as bad as MOH.

The idea is that GSM makes a call take less bandwidth.

The way it does it is by basically saying "ok, what is the most common call - voice, ok so lets make voice sound as good as possible at the expense of other calls".

Therefore, GSM will sound fine for voice (well, fine is subjective) but not for music.

So, WAV is good (although slin may be better) for MOH and GSM is the most commonly used voice codec.

By: Jason Parker (jparker) 2008-11-18 13:56:46.000-0600

I agree with davidw and ZX81 here.  Those are the basic reasons that these formats were chosen.