[asterisk-bugs] [Asterisk 0018723]: [patch] DTMF is always longer on the outbound call leg

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=18723 
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Reported By:                oej
Assigned To:                
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Project:                    Asterisk
Issue ID:                   18723
Category:                   Core/RTP
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Asterisk Version:           1.4.39.1 
JIRA:                        
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases):  1.4  
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2011-02-01 05:41 CST
Last Modified:              2011-02-01 07:55 CST
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Summary:                    [patch] DTMF is always longer on the outbound call
leg
Description: 
If two SIP phones is bridged over Asterisk, Asterisk will always add length
to the DTMF audio. The primary causes are:

 - DTMF duration is added with 160 ms for each BEGIN packet. The DTMF
Begin is transmitted three times and should have the same duration
 - One extra DTMF continue packet is generated directly after the BEGIN
packets and adds another 160 ms
 - The END packet shows the actual inbound duration + 160 since the CONT
code adds 160 after sending

The attached patch solves these issues. I am not proud over parts of the
code, but found no other simple way to fix the extra continue packet. Ideas
are welcome.

This seems to affect all released versions of Asterisk
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 (0131343) oej (manager) - 2011-02-01 07:55
 https://issues.asterisk.org/view.php?id=18723#c131343 
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RFC 2833 says: "An audio source SHOULD start transmitting event packets as
soon as it
   recognizes an event and every 50 ms thereafter or the packet interval
   for the audio codec used for this session, if known."

This gateway sends 50 ms... 

And yes, I have confused "timestamp units" and "ms" above. 

Issue History 
Date Modified    Username       Field                    Change               
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2011-02-01 07:55 oej            Note Added: 0131343                          
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