Problem with :missing_bundle_group error

[ndrean]

I am following your examples and have the error :missing_bundle_group almost right at the beginning.

The presence of the "bundle group" is ensure here in your lib:

ex_webrtc/lib/ex_webrtc/sdp_utils.ex

Line 34 in ae1e49f

def ensure_bundle(sdp) do

I imagine that my SDP below is "bad" but what is the reason?

%ExWebRTC.SessionDescription{
  type: :offer,
  sdp: "v=0\r\no=- 7650321100484192730 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=extmap-allow-mixed\r\na=msid-semantic: WMS\r\n"
}

How do I get it?

The JS is straightforward:

localPC = new RTCPeerConnection(PCCONFIG);
const offer = await localPC.createOffer();
await localPC.setLocalDescription(offer);
channel.push("signaling", JSON.stringify(localPC.localDescription));

The Channel handle_in calls the Room.receive_signaling_msg. This function fails to set_remote_description and outputs :missing_bundle_group.

For debugging, I made this function verbose.

case Jason.decode!(msg) do
      %{"type" => "offer"} = offer ->
        with {:sd, desc} <-
               {:sd, SessionDescription.from_json(offer)},
             {:pc_srd, :ok} <-
               {:pc_srd, PeerConnection.set_remote_description(state.pc, desc)},
             {:pc_ca, {:ok, answer}} <-
               {:pc_ca, PeerConnection.create_answer(state.pc)},
             {:pc_sld, :ok} <-
               {:pc_sld, PeerConnection.set_local_description(state.pc, answer)} do
          msg = %{"type" => "answer", "sdp" => answer.sdp}
          send(state.channel, {:signaling, msg})
        else
          {step, error} ->
            Logger.error("Error creating answer: #{inspect({step, error})}")
        end

The state of the Room GS is:

state #=> %{
  pc: #PID<0.1405.0>,
  channel: #PID<0.1404.0>,
  room_id: "1",
  video_track: nil,
  video_depayloader: %ExWebRTC.RTP.VP8Depayloader{
    current_frame: nil,
    current_timestamp: nil
  },
  audio_track: nil
}

[LVala]

Your offer needs to contain at least one media line (m=audio 9 ...) that is bundled (so your bundle_policy in JS PeerConnection config is left as the default). If you add a track or a transceiver to your JS PeerConnection (pc.addTransceiver("audio") before creating the offer), it should work fine. Your offer will look something like this:

v=0
o=- 4738948488208954376 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0
a=extmap-allow-mixed
a=msid-semantic: WMS
m=audio 9 UDP/TLS/RTP/SAVPF 111 63 9 0 8 13 110 126
c=IN IP4 0.0.0.0
[...]
a=rtpmap:13 CN/8000
a=rtpmap:110 telephone-event/48000
a=rtpmap:126 telephone-event/8000
a=ssrc:2036947827 cname:diVrqm47zTuoJg1L
a=ssrc:2036947827 msid:- 93dfc694-1716-4e2e-9b85-79665fc482a1

We could allow empty offers, but I don't really see how that could be useful, can you share your usecase?
Besides that, we will make the error more descriptive, that's for sure.

[ndrean]

My use case is just my ignorance...

localStream = await navigator.mediaDevices.getUserMedia(MEDIACONSTRAINTS);

localPC = new RTCPeerConnection(PCCONFIG);

for (let track of localStream.getTracks()) {
   localPC.addTrack(track, localStream);
 }
^^^

const offer = await localPC.createOffer();
await localPC.setLocalDescription(offer);
channel.push("signaling", JSON.stringify(localPC.localDescription));

sdp:

v=0
o=- 7695634337231338917 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0 1
a=extmap-allow-mixed
a=msid-semantic: WMS 1e66734f-56b2-457e-a057-b7ae1ab4cd0a
m=audio 9 UDP/TLS/RTP/SAVPF 111 63 9 0 8 13 110 126
c=IN IP4 0.0.0.0
[...]
a=ssrc:4032162308 msid:1e66734f-56b2-457e-a057-b7ae1ab4cd0a c9969ccc-a5f0-4009-a716-3e3bc3f493b6
m=video 9 UDP/TLS/RTP/SAVPF 96 97 102 103 104 105 106 107 108 109 127 125 39 40 45 46 98 99 100 101 112 113 116 117 118
c=IN IP4 0.0.0.0
[...]

[LVala]

No worries, always happy to help!