Add track_id to packets sent in {:rtcp, ...} message

examples/echo/lib/echo/peer_handler.ex

@@ -131,7 +131,7 @@ defmodule Echo.PeerHandler do
   defp handle_webrtc_msg({:rtcp, packets}, state) do
     for packet <- packets do
       case packet do
-        %ExRTCP.Packet.PayloadFeedback.PLI{} when state.in_video_track_id != nil ->
+        {track_id, %ExRTCP.Packet.PayloadFeedback.PLI{}} when state.in_video_track_id != nil ->
           Logger.info("Received keyframe request. Sending PLI.")
           :ok = PeerConnection.send_pli(state.peer_connection, state.in_video_track_id, "h")
 

examples/whip_whep/lib/whip_whep/forwarder.ex

@@ -119,7 +119,7 @@ defmodule WhipWhep.Forwarder do
   def handle_info({:ex_webrtc, _pc, {:rtcp, packets}}, state) do
     for packet <- packets do
       case packet do
-        %ExRTCP.Packet.PayloadFeedback.PLI{} when state.input_pc != nil ->
+        {_track_id, %ExRTCP.Packet.PayloadFeedback.PLI{}} when state.input_pc != nil ->
           :ok = PeerConnection.send_pli(state.input_pc, state.video_input)
 
         _other ->

lib/ex_webrtc/peer_connection.ex

@@ -65,6 +65,9 @@ defmodule ExWebRTC.PeerConnection do
   * `:track_muted`, `:track_ended` - these match the [MediaStreamTrack events](https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamTrack#events).
   * `:rtp` and `:rtcp` - these contain packets received by the PeerConnection. The third element of `:rtp` tuple is a simulcast RID and is set to `nil` if simulcast
   is not used.
+  * each of the packets in `:rtcp` message is in the form of `{track_id, packet}` tuple, where `track_id` is the id of the corrsponding track.
+  In case of PLI and NACK, this is the id of an outgoing (sender's) track id, in case of Sender and Receiver Reports - incoming (receiver's) track id.
+  If matching to a track was not possible (like in the case of TWCC packedts), `track_id` is set to `nil`.
   """
   @type message() ::
           {:ex_webrtc, pid(),
@@ -78,7 +81,7 @@ defmodule ExWebRTC.PeerConnection do
            | {:track_muted, MediaStreamTrack.id()}
            | {:track_ended, MediaStreamTrack.id()}
            | {:rtp, MediaStreamTrack.id(), String.t() | nil, ExRTP.Packet.t()}}
-          | {:rtcp, [ExRTCP.Packet.packet()]}
+          | {:rtcp, [{MediaStreamTrack.id() | nil, ExRTCP.Packet.packet()}]}
 
   #### NON-MDN-API ####
 
@@ -1134,9 +1137,10 @@ defmodule ExWebRTC.PeerConnection do
   def handle_info({:dtls_transport, _pid, {:rtcp, data}}, state) do
     case ExRTCP.CompoundPacket.decode(data) do
       {:ok, packets} ->
-        state =
-          Enum.reduce(packets, state, fn packet, state ->
-            handle_rtcp_packet(state, packet)
+        {packets, state} =
+          Enum.map_reduce(packets, state, fn packet, state ->
+            {track_id, state} = handle_rtcp_packet(state, packet)
+            {{track_id, packet}, state}
           end)
 
         notify(state.owner, {:rtcp, packets})
@@ -1796,20 +1800,31 @@ defmodule ExWebRTC.PeerConnection do
     end
   end
 
+  defp handle_rtcp_packet(state, %ExRTCP.Packet.ReceiverReport{} = report) do
+    with true <- :rtcp_reports in state.config.features,
+         {:ok, mid} <- Demuxer.demux_ssrc(state.demuxer, report.ssrc),
+         {_idx, transceiver} <- find_transceiver(state.transceivers, mid) do
+      {transceiver.receiver.track.id, state}
+    else
+      _other ->
+        {nil, state}
+    end
+  end
+
   defp handle_rtcp_packet(state, %ExRTCP.Packet.SenderReport{} = report) do
     with true <- :rtcp_reports in state.config.features,
          {:ok, mid} <- Demuxer.demux_ssrc(state.demuxer, report.ssrc),
          {idx, transceiver} <- find_transceiver(state.transceivers, mid) do
       transceiver = RTPTransceiver.receive_report(transceiver, report)
       transceivers = List.replace_at(state.transceivers, idx, transceiver)
-      %{state | transceivers: transceivers}
+      {transceiver.receiver.track.id, %{state | transceivers: transceivers}}
     else
       false ->
-        state
+        {nil, state}
 
       _other ->
         Logger.warning("Unable to handle RTCP Sender Report, packet: #{inspect(report)}")
-        state
+        {nil, state}
     end
   end
 
@@ -1820,19 +1835,21 @@ defmodule ExWebRTC.PeerConnection do
       |> Enum.find(fn {tr, _idx} -> tr.sender.ssrc == nack.media_ssrc end)
       |> case do
         nil ->
-          state
+          {nil, state}
 
         # in case NACK was received, but RTX was not negotiated
         # as NACK and RTX are negotiated independently
-        {%{sender: %{rtx_pt: nil}}, _idx} ->
-          state
+        {%{sender: %{rtx_pt: nil}} = tr, _idx} ->
+          {tr.sender.track.id, state}
 
         {tr, idx} ->
           {packets, tr} = RTPTransceiver.receive_nack(tr, nack)
           for packet <- packets, do: send_rtp(self(), tr.sender.track.id, packet, rtx?: true)
           transceivers = List.replace_at(state.transceivers, idx, tr)
-          %{state | transceivers: transceivers}
+          {tr.sender.track.id, %{state | transceivers: transceivers}}
       end
+    else
+      {nil, state}
     end
   end
 
@@ -1842,16 +1859,16 @@ defmodule ExWebRTC.PeerConnection do
     |> Enum.find(fn {tr, _idx} -> tr.sender.ssrc == pli.media_ssrc end)
     |> case do
       nil ->
-        state
+        {nil, state}
 
       {tr, idx} ->
         tr = RTPTransceiver.receive_pli(tr, pli)
         transceivers = List.replace_at(state.transceivers, idx, tr)
-        %{state | transceivers: transceivers}
+        {tr.sender.track.id, %{state | transceivers: transceivers}}
     end
   end
 
-  defp handle_rtcp_packet(state, _packet), do: state
+  defp handle_rtcp_packet(state, _packet), do: {nil, state}
 
   defp do_get_description(nil, _candidates), do: nil
 

test/ex_webrtc/peer_connection_test.exs

@@ -219,7 +219,7 @@
     assert_receive {:ex_webrtc, _pid, {:connection_state_change, :new}}
   end
 
   test "send_rtp/4" do
     {:ok, pc1} = PeerConnection.start_link()
     {:ok, pc2} = PeerConnection.start_link()
     track = MediaStreamTrack.new(:audio)
@@ -998,6 +998,70 @@
 
   # MISC TESTS
 
+  describe "RTCP" do
+    test "sends and handles PLI" do
+      # turn off features in order to not receive unwanted RTCP packets
+      {:ok, pc1} = PeerConnection.start_link(features: [])
+      {:ok, pc2} = PeerConnection.start_link(features: [])
+
+      %MediaStreamTrack{id: id1} = track = MediaStreamTrack.new(:video)
+      {:ok, _sender} = PeerConnection.add_track(pc1, track)
+
+      :ok = negotiate(pc1, pc2)
+      :ok = connect(pc1, pc2)
+
+      assert_receive {:ex_webrtc, ^pc2, {:track, %MediaStreamTrack{kind: :video, id: id2}}}
+
+      # we have to send something on the track, otherwise pc2 won't know the ssrc of its track
+      :ok = PeerConnection.send_rtp(pc1, track.id, ExRTP.Packet.new(<<3, 2, 5>>))
+      assert_receive {:ex_webrtc, ^pc2, {:rtp, ^id2, _rid, _packet}}
+
+      assert :ok = PeerConnection.send_pli(pc2, id2)
+
+      assert_receive {:ex_webrtc, ^pc1, {:rtcp, [{^id1, pli}]}}
+      assert %ExRTCP.Packet.PayloadFeedback.PLI{} = pli
+    end
+
+    test "sends NACK" do
+      # turn off features in order to not receive unwanted RTCP packets
+      {:ok, pc1} =
+        PeerConnection.start_link(features: [:inbound_rtx, :outbound_rtx], rtcp_feedbacks: [])
+
+      {:ok, pc2} =
+        PeerConnection.start_link(features: [:inbound_rtx, :outbound_rtx], rtcp_feedbacks: [])
+
+      %MediaStreamTrack{id: id1} = track = MediaStreamTrack.new(:video)
+      {:ok, _sender} = PeerConnection.add_track(pc1, track)
+
+      :ok = negotiate(pc1, pc2)
+      :ok = connect(pc1, pc2)
+
+      assert_receive {:ex_webrtc, ^pc2, {:track, %MediaStreamTrack{kind: :video, id: id2}}}
+
+      # we have to send something on the track, otherwise pc2 won't know the ssrc of its track
+      :ok =
+        PeerConnection.send_rtp(
+          pc1,
+          track.id,
+          ExRTP.Packet.new(<<3, 2, 5>>, sequence_number: 100)
+        )
+
+      assert_receive {:ex_webrtc, ^pc2, {:rtp, ^id2, _rid, _packet}}
+
+      :ok =
+        PeerConnection.send_rtp(
+          pc1,
+          track.id,
+          ExRTP.Packet.new(<<3, 2, 5>>, sequence_number: 102)
+        )
+
+      assert_receive {:ex_webrtc, ^pc2, {:rtp, ^id2, _rid, _packet}}
+
+      assert_receive {:ex_webrtc, ^pc1, {:rtcp, [{^id1, nack}]}}
+      assert %ExRTCP.Packet.TransportFeedback.NACK{nacks: [%{pid: 101}]} = nack
+    end
+  end
+
   describe "send data in both directions on a single transceiver" do
     test "using one negotiation" do
       {:ok, pc1} = PeerConnection.start_link()