Adding custom attribute in SDP

Asterisk Asterisk Support
1

Hello everyone.

I have a working Asterisk PBX (FreePBX). I’m configuring it to call a SIP client, which is an intercom.

With my current configuration, I can make a call to the intercom from another softphone, and the intercom is ringing.

But to make it work I have to add a custom SIP attribute in the initial SDP when establishing the call to the intercom. This attribute is a=DEVADDR:20

I do not need to add a SIP Header but a SIP SDP attribute.

I have search on the documentation, on internet and on the forum, without success.

Does someone has an idea on how to do such thing ?

Thanks

2

There is no such support written. You’d need to write C code to do so.

3

Thank you for the answer. I’m not a developer, but do you think it can be done by some sort of add-on or I have to modify asterisk source code and recompile it ?

4

I don’t know if we expose sufficient hooks to allow an external C module to do it, probably not.

5

That doesn’t appear to be an official SDP attribute and Google fails to find any unofficial use, but rather makes some guesses based on DevAddr being a term used by LoraWAN.

6

Yes I don’t think this is an official SDP attribute. This is used by Bticino intercom (C300X for me). And people trying to communicate with it using SIP needed a special patch for baresip (a SIP server).

But i’m already using asterisk/FreePBX so I want to integrate it with my current setup, avoiding to install baresip on another server

7

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