Hi All,
I am using Kamailio with rtpengine and have a parallel forking scenario (single
INVITE -> multiple branches via append_branch()).
Incoming INVITE has SDP with video
Goal:
- For Main branch : keep audio + video
- For Forked branch: strip video (audio only)
Problem:
SDP manipulation seems to be applied globally to the message, not per branch.
What I tried:
1. Using textops:
sdp_remove_media("video");
msg_apply_changes();
2. Trying to do it per branch:
I attempted to move this logic into branch_route, but msg_apply_changes() is
not allowed there, so SDP changes are not applied.
Documentation stated that it can be used from from REQUEST_ROUTE or REPLY_ROUTE.
3. Using rtpengine:
According to rtpengine NG protocol, "offer" supports:
"sdp-media-remove": ["video"]
However, I cannot find a way to pass this parameter via Kamailio's rtpengine
module.
Tried to add flag sdp-media-remove=video to the rtpengine_manage() but it
doesn't work.
Environment:
- Kamailio version: 6.0.6
- rtpengine version: 13.5.1.6
Question:
What is the correct way to modify SDP per branch in a parallel forking scenario
in Kamailio?
My test routing config:
```
request_route {
if (is_method("CANCEL")) {
if (t_check_trans()) {
route(RELAY);
}
exit;
}
if (!is_method("ACK")) {
if(t_precheck_trans()) {
t_check_trans();
exit;
}
t_check_trans();
}
# remove unused codecs and media
# if (has_body("application/sdp")) {
# sdp_remove_media("video");
# msg_apply_changes();
# }
if (is_method("INVITE") && !has_totag()) {
dlg_manage();
}
remove_hf("Route");
if (is_method("INVITE|SUBSCRIBE")) {
record_route();
}
if ($rU==$null) {
sl_send_reply("484","Address Incomplete");
exit;
}
route(LOCATION);
return;
}
route[RELAY] {
if (is_method("INVITE|BYE|SUBSCRIBE|UPDATE")) {
if(!t_is_set("branch_route")) t_on_branch("MANAGE_BRANCH");
}
if (is_method("INVITE|SUBSCRIBE|UPDATE")) {
if(!t_is_set("onreply_route")) t_on_reply("MANAGE_REPLY");
}
if (is_method("INVITE")) {
if(!t_is_set("failure_route")) t_on_failure("MANAGE_FAILURE");
}
if (!t_relay()) {
sl_reply_error();
}
exit;
}
route[LOCATION] {
route(ADD_FORK);
route(RELAY);
}
route[ADD_FORK] {
$avp(extNum) = "[email protected]";
append_branch("sip:" + $(avp(extNum)));
}
branch_route[MANAGE_BRANCH] {
route(NATMANAGE);
}
onreply_route[MANAGE_REPLY] {
# remove video media
# if (has_body("application/sdp")) {
# sdp_remove_media("video");
# msg_apply_changes();
# }
if(status=~"[12][0-9][0-9]") {
route(NATMANAGE);
}
}
failure_route[MANAGE_FAILURE] {
route(NATMANAGE);
if (t_is_canceled()) exit;
}
route[NATMANAGE] {
if (is_request()) {
if (has_body("application/sdp")) {
xlog("L_INFO","Negotiate RTP offer for branch $T_branch_idx\n");
if ($ru =~ "^sip:1[0-9]{4}@v") {
xlog("L_INFO","Main leg\n");
rtpengine_manage("replace-origin RTP/AVP external internal");
} else if ($ru =~ "192.168.106.34") {
xlog("L_INFO","Forked leg\n");
rtpengine_manage("replace-origin RTP/AVP codec-mask=telephone-event
transcode=PCMA always-transcode external internal via-branch=1");
//rtpengine_manage("label=$fu--->$ru sdp-media-remove=video
replace-origin RTP/AVP codec-mask=telephone-event transcode=PCMA
always-transcode ptime=20 external internal via-branch=1"); # only with patched
module
}
}
}
if (is_reply()) {
if (has_body("application/sdp") && (status=="200")) {
xlog("L_INFO","Negotiate RTP answer for branch $T_branch_idx\n");
}
}
return;
}
```
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