[asterisk-users] channel.c switches to gsm even when sip.conf only allows ulaw

[Kevin P. Fleming]

Jonas Arndt wrote:

> It does this without caring about the fact that you are ONLY allowing
> ulaw in the channel configuration. I have so far played with SIP but it
> seems the behavior is there for other channels as well (briefly tried it
> on IAX as well)
> 
> The problem with this is that some SIP providers (ViaTalk) only allows
> DTMF of the type inband, which only works on ulaw. Therefore this switch
> to GSM makes it impossible to enter the DISA or Authenticate password.

You are misunderstanding the message, and this why in general we ask
users who are not well versed in how Asterisk works to *not* enable the
DEBUG messages on the console.

What you are seeing is *not* Asterisk changing the format of the audio
stream between it and the provider, but instead it is changing the
internal 'write format' of the channel to GSM (by putting a GSM to ULAW
transcoder in the path). It is doing this because you are running an
application that wants to play sound files, and you don't have ULAW
sound files installed. Since the only sound files you have are GSM, it
has to transcode that to ULAW before sending it out the channel.

-- 
Kevin P. Fleming
Director of Software Technologies
Digium, Inc. - "The Genuine Asterisk Experience" (TM)