webrtcbin: configure rtpulpfecdec passthrough property

This allows downstream (payloaders mostly) to be able to correctly
detect actual packet loss from rtp sequence numbers.

See
https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/issues/581
for background.

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/1407

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3212>

diff --git a/subprojects/gst-plugins-bad/ext/webrtc/gstwebrtcbin.c b/subprojects/gst-plugins-bad/ext/webrtc/gstwebrtcbin.c
index 42c82f3..c16677d 100644 (file)
--- a/subprojects/gst-plugins-bad/ext/webrtc/gstwebrtcbin.c
+++ b/subprojects/gst-plugins-bad/ext/webrtc/gstwebrtcbin.c
@@ -4984,7 +4984,8 @@ _set_internal_rtpbin_element_props_from_stream (GstWebRTCBin * webrtc,
 
       try_match_transceiver_with_fec_decoder (webrtc, trans);
       if (trans->ulpfecdec) {
-        g_object_set (trans->ulpfecdec, "pt", ulpfec_pt, NULL);
+        g_object_set (trans->ulpfecdec, "passthrough", ulpfec_pt == 0, "pt",
+            ulpfec_pt, NULL);
       }
 
       if (trans->redenc) {