[asterisk-users] Codec Negotiation

[Martin Joseph]

On Jul 20, 2006, at 10:16 AM, Douglas Garstang wrote:

> I'm a little confused about Asterisk codec negotiation. Hopefully  
> someone can help.
>
> I have two phones, one on a slow link where I'd like to use G729,  
> and one on a fast link where I'd like to use ulaw.
>
> My sip.conf has:
>
> [general]
> allow=ulaw
> allow=g729
> ...
> [slow-phone]
> allow=g729
> allow=ulaw
>
> Firstly, does setting the codec for the slow-link phone override  
> the general settings? Of course it's not actually documented anywhere.
>
> When the fast link phone calls the slow link phone, it sends ulaw  
> and G729 in that order to Asterisk. When Asterisk relays the INVITE  
> to the slow link phone, it does not change the codec preference,  
> and sends ulaw followed by G729. I end up with a call that's ulaw  
> on both legs, which isn't what I want.
>
> I guess the settings in [slow-phone] aren't overriding the settings  
> in [general]. That's bad...
> How can I work around this?
As you already stated in your previous post the slow phone codec pref  
does override general when it's the caller.

I think the calling parties codec preferences are respected.  That is  
why I suggested the last time you posted this that you "force" the  
slow link to g729 (allow that only), as that will cause the calling  
party (fast) to choose g729 also...

I remember reading this described somewhere, but can't find the docs  
at the moment.

HTH,
Marty



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