[Asterisk-Users] FireFly and GS-BT100 codec negotiation problem

[Tim Robbins]

Willem de Groot wrote:

> Summary: how to force the alaw codec upon a call between Firefly & 
> Grandstream BT100?
>
> Not sure whether this is a problem with FireFly, with Asterisk, with 
> both or just with me ;-)
>
> I have:
>    disallow=all
>    allow=alaw
> in the general section of my sip.conf.
>
> Using Ethereal on the PC running FireFly, I get the following results.
>
> GS = grandstream BT100 initiating SIP call, FF = firefly receiving call
>
> * -> FF: invite from GS to FF (PCMA)
> FF -> *: OK (PCMA)
> * -> FF: reinvite to GS IP (PCMA, G723, PCMU, G726-32, G729, iLBC)
> FF -> *: OK (iLBC)
> GS -> FF: RTP stream (unanswered by FF)
> [...RTP monologue continues...]
> [...hangup on the GS...]
> GS -> FF: RTCP goodbye
> * -> FF: reinvite to * ip (PCMA)
> FF -> *: OK (PCMA)
> * -> FF: BYE
> FF -> *: OK
>
> Meanwhile on the *-console:
>    -- Attempting native bridge of SIP/grandstream-0f65 and 
> SIP/willem-2cbe
> Oct 18 15:15:39 WARNING[98311]: chan_sip.c:2804 process_sdp: No 
> compatible codecs!
> Oct 18 15:15:39 WARNING[98311]: chan_sip.c:2804 process_sdp: No 
> compatible codecs!
>
> Meanwhile on the FF PC with DebugView running:
> [368] Wrong input size for iLBC - requires 30ms frames
> [368] Stopping transmission due to send error
> [368] Finished reading
>
> Apparently FF does not accept 20ms iLBC frames (which is the default 
> on the GS phones).
>
> So my questions:
>
>    * Why is * advertising codecs in the reinvite request which
>      shouldn't be used according to sip.conf? It advertises fine in the
>      initial invite.
>    * Why does FF answer "OK (iLBC)" upon the reinvite request, even
>      though I have turned off the iLBC codec in FF's configuration?
>      Probably a bug with FF?
>    * Why does * croak "no compatible codecs" when in fact both sides
>      have pcma/alaw enabled and even advertise them? 

Which release of Firefly are you using? The iLBC frame size problem with 
SIP should be fixed in the current release (1.9.5).

As for why Firefly accepts iLBC even though you've turned it off: at the 
moment, the network settings don't affect the codecs that can be used 
for incoming SIP calls.


Tim