[Asterisk-Users] Asterisk Native Sound Distortion (ulaw)

[shadowym]

I too have noticed problems with Asterisk native sounds using ulaw on
Asterisk 1.2.9.1.  Don't know about other versions but it seems to work
quite well in Astlinux 0.40.  In theory, since I am using ulaw for SIP there
is no transcoding so it is a more efficient use of CPU resources and it
should sound much better in general.  It does sound better except for the
frequent cracles, pops, and momentary dropouts which makes it much more
objectionable to listen to compared to the standard GSM files.  

Is there a bug report on this yet? 

> -----Original Message-----
> From: Tim Panton [mailto:tim at mexuar.com] 
> Sent: Thursday, June 29, 2006 2:04 AM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] Standard Sound Files Distortion
> 
> 
> On 28 Jun 2006, at 19:50, Douglas Garstang wrote:
> 
> >> -----Original Message-----
> >> From: Doug Lytle [mailto:support at drdos.info]
> >> Sent: Wednesday, June 28, 2006 12:31 PM
> >> To: Asterisk Users Mailing List - Non-Commercial Discussion
> >> Subject: Re: [Asterisk-Users] Standard Sound Files Distortion
> >>
> >>
> >> Douglas Garstang wrote:
> >>> I've been noticing lately what seems to be some distortian
> >> in the standard asterisk sound files, used for voicemail.
> >> These files are stored on the local Asterisk system. When Asterisk 
> >> plays them, I can hear some cracles and pops. I'd never 
> noticed these 
> >> until recently.
> >>>
> >>>
> >> What I've learned from reading the list, is it usually is 
> a sign of 
> >> shared IRQs.  Just a thought.
> >
> > Thanks for the reply. I just worked out what it was. I had 
> ulaw copies 
> > of all the sound files in the digits/ directory. For some 
> reason, the 
> > ulaw files either had the cracks and pops in the 
> recordings, or when 
> > asterisk played the ulaw files, it generated the cracks and pops.
> 
> I've noticed something that may (or may not) be related.
> 
> If you have a sound file that isn't an exact multiple of 20ms 
> long, then asterisk 1.2.9.1 (don't know about other versions 
> - yet) sends out a 'partial' packet with the remaining data 
> in it. For ulaw, the data would normally be 160 bytes, but a 
> few (the last?) packet(s) might be 54 bytes (or whatever). 
> This confuses my softphone.
> Do we think this is correct behavior ? Shouldn't asterisk pad 
> the sound out to 20ms?
> 
> Note - this never occurs with GSM data, like the 'standard' 
> voice files, as gsm is always a multiple of 20ms long.
> 
> T.
> 
> Tim Panton
> tim at mexuar.com
> 
> 
> 
> 
>