[asterisk-bugs] [Asterisk 0016665]: DTMF not detected at all from Sipgate despite TCPDump showing keypresses

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=16665 
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Reported By:                d_richards
Assigned To:                
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Project:                    Asterisk
Issue ID:                   16665
Category:                   Core/RTP
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     acknowledged
Asterisk Version:           1.6.2.1 
JIRA:                       SWP-775 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2010-01-21 03:29 CST
Last Modified:              2010-03-24 13:48 CDT
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Summary:                    DTMF not detected at all from Sipgate despite
TCPDump showing keypresses
Description: 
V: 1.6.2.1

Issue is with incoming calls from ITSP 'Sipgate'. DTMF keypresses are not
detected when they enter Sipgate from the PSTN network, despite being
clearly visible with a TCPDump. There are some very slight differences in
the events:
(this may help to visualise:
http://www.fotobytes.co.uk/user22171/dtmf_debug.php )

WORKING DETECTION:
1... .... = Marker: True
Payload type: telephone-event (101)
..00 0000 = Volume: 0
Event Duration: 480

FAILED DETECTION:
0... .... = Marker: False
Payload type: Unknown (101)
..00 1010 = Volume: 10
Event Duration: 1280

Initially considered this to be config/Sipgate but after several weeks of
tweaking, changes, reading up and consultation with Sipgate this looks like
Asterisk could be to blame. Have tried with Linksys ATA and it detects the
DTMF coming in from Sipgate flawlessly, which tends to support the issue is
at least partially with Asterisk.
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 (0119846) sharpone (reporter) - 2010-03-24 13:48
 https://issues.asterisk.org/view.php?id=16665#c119846 
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Sure, rfc2833 is out of band, however why the need for a volume indicator
in the first place since rfc2833 is out of band? The answer is most likely
that somewhere down the line of the call, DTMF must be translated and go
inband (i.e. if the destination is still analog), otherwise there would be
no need of volume/signal level at all. 

I'm no expert either, it's just a hypothesis, but one which for all
intents and purposes seems to be correct in my limited testing. I rolled
back to 1.4.26 last night and tested all of the numbers that our employees
had complained about DTMF not recognizing, or requiring multiple presses to
recognize. The result, every single number worked with single presses of
keys, every time. Analyzing the packet dumps showed the ONLY difference in
the RTP EVENT packets to be the volume bits were 5 instead of 10
(decimal).

According to the RFC: "The [volume] range of valid DTMF is from 0 to -36
dBm0 (must accept)" however, in practice -5 is the lowest I've been able to
go and still have reliable detection on the destinations we are calling. 

Issue History 
Date Modified    Username       Field                    Change               
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2010-03-24 13:48 sharpone       Note Added: 0119846                          
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