Hello David,

are you using another module or function that also works on the SDP? Then they probably interfere with each other.

Regarding the video topic, have a look to the sdpops module, sdp_with_media for example.

Cheers,

Henning

Henning Westerholt – https://skalatan.de/blog/

From: David Cunningham via sr-users <sr-users@lists.kamailio.org>
Sent: Mittwoch, 17. Dezember 2025 02:09
To: Kamailio (SER) - Users Mailing List <sr-users@lists.kamailio.org>
Cc: David Cunningham <dcunningham@voisonics.com>
Subject: [SR-Users] Replacing an attribute in the SDP

Hello,

We need to replace a=sendrecv with a=sendonly in the 200 OK reply to an INVITE. In theory it should be something straightforward, like in the onreply_route using:

replace_body_all( "a=sendrecv", "a=sendonly" );

or:

subst_body( '/^a=sendrecv/a=sendonly/' )

Our first problem is that these both are appending a=sendonly to the end of the SDP, not replacing values within it. Does anyone know why this might happen?

Our second problem is that we really only want to do this for video media, and not touch the audio media. Are there any text tools that allow you to work with specific media within the SDP?

Thanks in advance for any tips!

David Cunningham, Voisonics Limited
http://voisonics.com/
USA: +1 213 221 1092
New Zealand: +64 (0)28 2558 3782