[OpenSIPS-Users] rtpengine transcoding

Alexey Kazantsev kurgan-rus at inbox.ru
Thu Jun 21 04:06:02 EDT 2018

Hi list,

I'm trying to establish a successfull call with RTP through OpenSIPS,
with transcoding PCMA <---> PCMU and vice versa.

Debian 9.4 stable (Stretch)
OpenSIPS 2.4.1
RTPEngine Version:

RTPEngine is OK:
root at debian-opensips:/etc/opensips# rtpengine --codecs
                PCMA: fully supported
                PCMU: fully supported

The 'rtpengine' module also works fine, as I see how the ip addresses
in SDP are rewritten after leaving OpenSIPS.

But I can not configure transcoding. I tried many variants of flags in
'rtpengine_offer' function:

  rtpengine_offer("RTP/AVP replace-origin replace-session-connection ICE=remove codec-mask-PCMA codec-strip-PCMU transcode-PCMU"))

And in this ^^^ case I tried to do the same but on the contrary in the 'rtpengine_answer':

  rtpengine_answer("RTP/AVP replace-origin replace-session-connection ICE=remove codec-mask-PCMU codec-strip-PCMA transcode-PCMA");

I also tried offer with code-related flags, and answer with no flags.
I also tried another variant of offer with the 'always-transcode' flag:

  rtpengine_offer("RTP/AVP replace-origin replace-session-connection ICE=remove always-transcode");

Still the same. Can not make in do transcoding.
Of course I can route the calls through Asterisk, but I'm trying to configure transcoding via RTPEngine.

So, what I'm doing wrong?!

BR, Alexey

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