[asterisk-bugs] [Asterisk 0015296]: TDM call over IAX trunk gives choppy audio, SIP call over same IAX trunk sounds fine.

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=15296 
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Reported By:                alecdavis
Assigned To:                
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Project:                    Asterisk
Issue ID:                   15296
Category:                   Channels/chan_iax2
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
Asterisk Version:           1.6.1.0 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): 1.6.1 
SVN Revision (number only!): 199300 
Request Review:              
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Date Submitted:             2009-06-09 07:03 CDT
Last Modified:              2009-06-11 06:31 CDT
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Summary:                    TDM call over IAX trunk gives choppy audio, SIP call
over same IAX trunk sounds fine.
Description: 
Testing to an Asterisk 1.4.20 -> Milliwatt application.
Also tested to an elderly 1.6.x r178446M release. same problems.

senarios are as below:

Analog phone <-> FXS-TDM800P/Asterisk 1.6.1.0 <-IAX internet-> Asterisk
1.4.20 Milliwatt App.

SIP phone <-> Asterisk 1.6.1.0 <-IAX internet-> Asterisk 1.4.20 Milliwatt
App.

Analog phone audio sounds very choppy, SIP phone audio sounds fine.

Tried with GSM only IAX trunks, and ALAW only trunks, same result, no
improvement.


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 (0106285) alecdavis (reporter) - 2009-06-11 06:31
 https://issues.asterisk.org/view.php?id=15296#c106285 
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Tonight tested between 2 locally connected on the same ethernet switch.

CISCO 7912 <-> BOX1 IAX <-> 100M SWITCH <-BOX2 IAX-> Milliwatt App

The symptom as the audio from the Milliwatt generator cuts out after 2-3
seconds every time noise is made at the CISCO end, IE a packet is
transmitted, which then restarts the packets being sent from the remote
Milliwatt app.

Surely, the Milliwatt generator is 'talking' all the time, so packets
should be coming to the CISCO?

This I believe is the answer, packets are sent asynchrounously, one
received, one sent, where the Milliwatt app is the slave, the Cisco is the
master.

I have enabled 'internal_timing' in asterisk.conf and that fixes the CISCO
silence issue, but I think that IAX is switching in and out of synchronous
mode and asynchronous mode when packets arn't received, thus if network
jitter is present in both directions, the audio sounds twice as bad. 

Issue History 
Date Modified    Username       Field                    Change               
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2009-06-11 06:31 alecdavis      Note Added: 0106285                          
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