[asterisk-bugs] [Asterisk 0012437]: Asterisk negotiates only T.38 when answering even if the other end offers audio

[Asterisk Bug Tracker]

The following issue requires your FEEDBACK. 
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http://bugs.digium.com/view.php?id=12437 
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Reported By:                marsosa
Assigned To:                file
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Project:                    Asterisk
Issue ID:                   12437
Category:                   Channels/chan_sip/T.38
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     feedback
Asterisk Version:           1.4.18 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2008-04-14 08:31 CDT
Last Modified:              2009-02-18 08:51 CST
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Summary:                    Asterisk negotiates only T.38 when answering even if
the other end offers audio
Description: 
One of our gateways (audiocodes mp-118) offers ulaw,g729 and t.38 when an
incoming call is sent to asterisk, and asterisk answer() with t.38 only,
instead of using ulaw. T.38 is enabled on the gateway because this is
needed for reinvites, if i disable it, the call works ok but fails later
when the ata wants to do reinvite for receiving faxes with t.38 '488 not
acceptable'.
The main problem here is that, after answering with t.38, asterisk sends
invites with t.38 only to the ip phones, and they rejected with not
acceptable.
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 (0100302) file (administrator) - 2009-02-18 08:51
 http://bugs.digium.com/view.php?id=12437#c100302 
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I've created a branch at
http://svn.digium.com/svn/asterisk/team/file/issue12437 that has a few
changes to hopefully better handle an initial INVITE with T38.

chan_sip will now respond with SDP that includes the different media
streams offered. For example if an INVITE comes in with both audio and T38
we will now respond back with audio and T38.

For the outgoing call from a channel that has both audio and T38 we will
only offer audio initially. If T38 packets come in we will then trigger a
reinvite to T38. I did it this way since reinvites seem to have the best
compatibility between devices.

Please give it a go and provide any feedback. I've done what testing I can
with what I have. 

Issue History 
Date Modified    Username       Field                    Change               
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2009-02-18 08:51 file           Note Added: 0100302                          
2009-02-18 08:51 file           Status                   assigned => feedback
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