Hello,

On 19/06/15 11:52, Sebastian Damm wrote:

Hi,

we have some cases, where we get multiple PCMA lines with different numbers from a peer. One of our backend systems doesn't handle that correctly. So what I want to do is detect whether there is a PCMA line with a non-standard number in the SDP.

This is how an SDP looks like: v=0 o=hiQ9200 2990220150519102450 1229717573 IN IP4 1.2.3.4 s=Phone Call c=IN IP4 1.2.3.4 t=0 0 m=audio 40174 RTP/AVP 8 0 18 96 97 13 100 98 99 a=rtpmap:8 PCMA/8000 a=fmtp:8 vad=no a=rtpmap:0 PCMU/8000 a=fmtp:0 vad=no a=rtpmap:18 G729/8000 a=fmtp:18 annexb=yes a=rtpmap:96 G726-32/8000 a=rtpmap:97 AAL2-G726-32/8000 a=rtpmap:100 telephone-event/8000 a=fmtp:100 0-15 a=rtpmap:98 PCMA/8000 a=gpmd:98 vbd=yes a=rtpmap:99 PCMU/8000 a=gpmd:99 vbd=yes a=sqn: 0 a=cdsc: 1 image udptl t38 a=sendrecv a=pmft: T38 a=ptime:20

I tried something like that (expecting that the number doesn't change):

if (sdp_get_line_startswith("$avp(badcodec)", "a=rtpmap:98 PCMA")) {

But this makes Kamailio drop the INVITE when arriving at the line in the config. I guess, "startswith" stops parsing the line at the colon.

there was a bug returning 0 in case of a no match. I just pushed a fix in master, going to backport it.

So I thought I'll make it more generically:

sdp_get("$avp(sdp)"); if ($avp(sdp) =~ "a=rtpmap:([1-9][0-9][0-9]?) PCMA") { sdp_remove_codecs_by_id("$missingvariable"); }

What I need is to capture the number in the a=rtpmap line so I can delete the codec by ID. But I couldn't find a way to capture the matches from my regex comparison. Am I missing something?

Maybe you can use the subst transformation here.

Cheers, Daniel