[asterisk-dev] [Code Review] Keep RTP DTMF short and sweet

Olle E Johansson reviewboard at asterisk.org
Tue Feb 1 05:57:59 CST 2011

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Review request for Asterisk Developers.


Asterisk by default adds 740 ms to every outbound DTMF in the RTP subsystem. For longer DTMF key presses, it doesn't matter much, but for very short ones, it adds a LOT of extra noise in the call. Unfortunately, we had a lot of very short DTMF and got complains.

- 2*160 ms in the retransmits of DTMF begin packets. They all should have the same duration
- 160 ms in an extra DTMF continue packet that doesn't match any incoming packet
- 160 ms by bad calculation in the DTMF end packet

This code fixes all of these issues and make sure that outbound DTMF has the same duration as inbound DTMF on the RTP channel. I am not proud over the code that stops the extra DTMF continue though. Will try to come up with something more cool. This works though. Feedback and ideas are more than welcome.

This addresses bug 18723.


  /branches/1.4/main/rtp.c 304949 

Diff: https://reviewboard.asterisk.org/r/1091/diff


Tested beeping with Asterisk 1.6.0 between two SNOM phones many many times. Will continue testing on production servers.


Olle E

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