[Asterisk-Users] Polycom DTMF

[Greg Boehnlein]

On Thu, 24 Mar 2005, David Gomillion wrote:

> Problem:
>    Polycom SoundPoint IP phones (running SIP) ceases to send DTMF that
> Asterisk can detect and use.  It worked in 1.0.5, but has not worked
> since.  This has been verified on SoundPoint IP 300's and SoundPoint IP
> 600's.
> 
> Workaround:
>    It used to be that for DTMF to work, I had to set the mode in
> sip.conf to "inband".  Without making any configuration changes on the
> phones, I changed the DTMF mode to "rfc2833".  The DTMF is recognized.
> No reboot to the phone is necessary, and remember that you can reload
> the sip configuration with a reload in Asterisk, meaning your PBX
> doesn't have to be restarted either.
> 
> Discussion:
>    This is probably not the "right" way to fix this, as Polycom's
> configurations, by default, will "encode DTMF in the active RTP stream".
> There may have been a change in the sip channel's code that is causing
> this.  Others on the list have indicated that they worked around the
> problem by reverting the version of the sip app to an older version.
>    As the new code usually fixes other problems, the solution of
> reverting seemed to be counter-productive, so I tried other DTMF
> signalling modes.  Thankfully, the stock Polycom configs will work with
> Asterisk's sip.conf "rfc2833" DTMF mode, at least as of
> CVS-v1-0-03/23/05-21:40:48.  When I get more time, or if someone else
> has the time, an examination of what changed to cause this could enable
> us to fix the heart of the matter.
>    Other users on the Asterisk list (see thread "*-1.0.7 DTFM => Not
> working" from 03/23/2005) have reported other UAs not working.
> Therefore, there may be a bigger problem with the fundamental issue at
> hand: when do we change DTMF in channels, to ensure compliance with
> standards, as well as compatibility with older UAs.  
> 
> Hope this helps someone.
> 
> Sincerely,
> David Gomillion

David,
	I noticed this in testing the 1.0.7 Release Candidate w/ my 
Polycom phones. I posted the following in 
http://bugs.digium.com/bug_view_page.php?bug_id=0003746

03-16-05 16:05
Alright. I updated my Development and Home PBXs to 1.0.7 w/ Slepp's Dundi 
1.0.2_diff-4 patch. Both are running solid. One issue that I noticed is 
that my Polycom SP IP phones had to be changed to use RFC2833 signalling 
instead of the Inband signalling I had been using earlier. I simply 
modified the sip.conf to have "dtmfmode=rfc2833". This proved to be a 
slight gotcha for a couple of clients when I updated THEIR boxes. This 
could be just a fluke, and I may be an idiot for having used inband DTMF 
in the first place, but it is something to be concious of. Can anyone 
pinpoint a specific SIP patch that may have been applied where this may 
have been affected? How should this be handled? Should I add it as a new 
bug-note? Or should we just chalk it up and slap a notice in the release 
notes? Should inband signaling be broken in 1.0.7 for Polycom phones? Or 
should it work? I guess this is the question that needs to be asked.. is 
it normal behaviour or a bug? I'm not sure if this is related, but I also 
enabled MMX math routines for Zaptel.

I never got any followup on it before 1.0.7 was dropped.

I'm going to open up a new bug report on this in Mantis and see what we 
can get as far as comments.

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