Add medium encoding and expose FIR interval in WebRTC Endpoint options

assets/js/const.ts

@@ -13,6 +13,11 @@ export const simulcastConfig: RTCRtpTransceiverInit = {
       scaleResolutionDownBy: 4.0,
       //   scalabilityMode: "L1T" + TEMPORAL_LAYERS_COUNT,
     },
+    {
+      rid: "m",
+      active: true,
+      scaleResolutionDownBy: 2.0,
+    },
     {
       rid: "h",
       active: true,

assets/js/membraneWebRTC.ts

@@ -389,9 +389,9 @@ export class MembraneWebRTC {
    * receive in {@link onPeerJoined}. E.g. this can source of the track - wheather it's
    * screensharing, webcam or some other media device.
    * @param isSimulcast - Defines whether track should be simulcasted or not.
-   * At the moment simulcast track is sent in two versions - low and high.
-   * High resolution is the original track resolution while the low resolution
-   * is the original track resoultion scaled down by 4.
+   * At the moment simulcast track is sent in three versions - low, medium and high.
+   * High resolution is the original track resolution, while medium and low resolutions
+   * are the original track resoultion scaled down by 2 and 4 respectively.
    * Those settings are not configurable at the moment.
    * @returns {string} Returns id of added track
    * @example

lib/membrane_rtc_engine/endpoints/webrtc/forwarder.ex

@@ -35,7 +35,7 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.Forwarder do
                 :old_encoding,
                 selected_encoding: "h",
                 vp8_munger: VP8Munger.new(),
-                active_encodings: ["h", "l"],
+                active_encodings: ["h", "m", "l"],
                 started?: false
               ]
 
@@ -67,7 +67,7 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.Forwarder do
         active_encodings: List.delete(forwarder.active_encodings, encoding)
     }
 
-    do_select_encoding(forwarder, List.first(forwarder.active_encodings))
+    do_select_encoding(forwarder, get_next_encoding(forwarder.active_encodings))
   end
 
   def encoding_inactive(forwarder, encoding) do
@@ -101,7 +101,7 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.Forwarder do
 
       # if we don't have any active encoding
       forwarder.selected_encoding == nil ->
-        do_select_encoding(forwarder, List.first(forwarder.active_encodings))
+        do_select_encoding(forwarder, get_next_encoding(forwarder.active_encodings))
 
       true ->
         forwarder
@@ -146,6 +146,22 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.Forwarder do
     %__MODULE__{forwarder | queued_encoding: encoding}
   end
 
+  defp get_next_encoding(encodings) do
+    encodings |> sort_encodings() |> List.first()
+  end
+
+  defp sort_encodings(encodings) do
+    get_value = fn encoding ->
+      case encoding do
+        "h" -> 3
+        "m" -> 2
+        "l" -> 1
+      end
+    end
+
+    Enum.sort(encodings, fn e1, e2 -> get_value.(e1) > get_value.(e2) end)
+  end
+
   @spec process(t(), Membrane.Buffer.t(), Endpoint.WebRTC.encoding_t(), any()) ::
           {t(), [Membrane.Element.Action.t()]}
   def process(%__MODULE__{started?: false} = forwarder, buffer, encoding, endpoint_id) do

lib/membrane_rtc_engine/endpoints/webrtc/simulcast_tee.ex

@@ -32,7 +32,11 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.SimulcastTee do
      %{
        clock_rate: opts.clock_rate,
        forwarders: %{},
-       trackers: %{"l" => EncodingTracker.new("l"), "h" => EncodingTracker.new("h")},
+       trackers: %{
+         "l" => EncodingTracker.new("l"),
+         "m" => EncodingTracker.new("m"),
+         "h" => EncodingTracker.new("h")
+       },
        update?: false
      }}
   end

lib/membrane_rtc_engine/endpoints/webrtc_endpoint.ex

@@ -138,6 +138,15 @@ if Code.ensure_loaded?(Membrane.WebRTC.EndpointBin) do
                   default: nil,
                   description:
                     "Sender reports's generation interval, set to nil to avoid reports generation"
+                ],
+                rtcp_fir_interval: [
+                  spec: Membrane.Time.t() | nil,
+                  default: Membrane.Time.second(),
+                  description: """
+                  Defines how often FIR should be sent.
+
+                  For more information refer to RFC 5104 section 4.3.1.
+                  """
                 ]
 
     def_input_pad :input,
@@ -183,7 +192,8 @@ if Code.ensure_loaded?(Membrane.WebRTC.EndpointBin) do
         integrated_turn_options: opts.integrated_turn_options,
         integrated_turn_domain: opts.integrated_turn_domain,
         owner: opts.owner,
-        video_tracks_limit: opts.video_tracks_limit
+        video_tracks_limit: opts.video_tracks_limit,
+        rtcp_fir_interval: opts.rtcp_fir_interval
       }
 
       {{:ok, spec: spec, log_metadata: opts.log_metadata}, state}
@@ -350,7 +360,7 @@ if Code.ensure_loaded?(Membrane.WebRTC.EndpointBin) do
             options: [
               extensions: extensions,
               use_depayloader?: false,
-              rtcp_fir_interval: Membrane.Time.seconds(5)
+              rtcp_fir_interval: state.rtcp_fir_interval
             ]
           )
           |> to_bin_output(pad)

test/membrane_rtc_engine/webrtc/forwarder_test.exs

@@ -9,9 +9,9 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.ForwarderTest do
 
     assert %Forwarder{
              selected_encoding: "h",
-             queued_encoding: "l",
+             queued_encoding: "m",
              old_encoding: "h",
-             active_encodings: ["l"]
+             active_encodings: ["m", "l"]
            } = forwarder
 
     forwarder = Forwarder.encoding_active(forwarder, "h")
@@ -20,7 +20,7 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.ForwarderTest do
              selected_encoding: "h",
              queued_encoding: nil,
              old_encoding: nil,
-             active_encodings: ["l", "h"]
+             active_encodings: ["m", "l", "h"]
            } = forwarder
   end
 end