[RTC-32] Fetch actual bitrate of a variant

internal_docs/webrtc_media_events.md

@@ -61,6 +61,7 @@ Messages used by any WebRTC Endpoint plugin
 | [candidate](#candidate)                         | Contains client's ICE candidate                                         |
 | [sdpOffer](#sdpoffer)                           | Contains an SDP offer from a client                                     |
 | [setTargetTrackVariant](#setTargetTrackVariant) | A request from a peer to receive a specific track variant               |
+| [trackVariantBitrates](#trackVariantBitrate)    | Contains updated bitrates for track's variants                          |
 
 #### WebRTC endpoint sends these type of custom messages to client
 | Name                                    | Description                                                       |
@@ -315,8 +316,9 @@ Messages used by any WebRTC Endpoint plugin
 
 ### `sdpOffer`
 
-* Contains an SDP offer, a mapping between `track_id` and `track_metadata`, and a mapping between `mid` and `track_id`.
-  Both maps contain only information about current peer `sendonly` tracks.
+* Contains an SDP offer, a mapping between `track_id` and `track_metadata`, mapping between `track_id` 
+  and this track's bitrates (or all of its variants bitrates) and a mapping between `mid` and `track_id`.
+  Maps contain only information about current peer `sendonly` tracks.
 
   ```json
   {
@@ -326,7 +328,10 @@ Messages used by any WebRTC Endpoint plugin
     },
     trackIdToTrackMetadata: {
       trackId: any
-    }
+    },
+    trackIdToTrackBitrates: {
+      trackId: number | {rid: number}
+    },
     midToTrackId: mid_to_track_id
   }
   ```
@@ -345,6 +350,18 @@ Messages used by any WebRTC Endpoint plugin
   }
   ```
 
+### `trackVariantBitrates`
+
+* Contains updated bitrates of variants of the track send by the peer.
+  Needs to contain all of the variants.
+
+```json
+{
+  trackId: track_id,
+  variantBitrates: {rid: number}
+}
+```
+
 ## WebRTC Enpoint -> Client
 
 ### `offerData`

lib/membrane_rtc_engine/endpoints/webrtc/media_event.ex

@@ -294,32 +294,28 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.MediaEvent do
             "midToTrackId" => mid_to_track_id
           } = data
       } ->
+        # use default bitrates in VariantSelector if not present
         default_bitrates =
           Map.new(track_id_to_track_metadata, fn {id, _metadata} -> {id, %{}} end)
 
-        rid_bitrates = Map.get(data, "trackIdToTrackBitrates", %{})
-
-        if is_map(rid_bitrates) do
-          bitrates =
-            Map.new(rid_bitrates, fn {id, bitrate} -> {id, to_track_variants(bitrate)} end)
-
-          {:ok,
-           %{
-             type: :sdp_offer,
-             data: %{
-               sdp_offer: %{
-                 type: :offer,
-                 sdp: sdp
-               },
-               track_id_to_track_metadata: track_id_to_track_metadata,
-               # use default values in VariantSelector if "trackIdToTrackBitrates" is not present
-               track_id_to_track_bitrates: Map.merge(default_bitrates, bitrates),
-               mid_to_track_id: mid_to_track_id
-             }
-           }}
-        else
-          {:error, :invalid_media_event}
-        end
+        track_id_to_track_bitrate =
+          data
+          |> Map.get("trackIdToTrackBitrates", default_bitrates)
+          |> Map.new(fn {id, bitrate} -> {id, to_track_variants(bitrate)} end)
+
+        {:ok,
+         %{
+           type: :sdp_offer,
+           data: %{
+             sdp_offer: %{
+               type: :offer,
+               sdp: sdp
+             },
+             track_id_to_track_metadata: track_id_to_track_metadata,
+             track_id_to_track_bitrates: track_id_to_track_bitrate,
+             mid_to_track_id: mid_to_track_id
+           }
+         }}
 
       _other ->
         {:error, :invalid_media_event}
@@ -357,5 +353,4 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.MediaEvent do
   end
 
   defp to_track_variants(bitrate) when is_number(bitrate), do: %{high: bitrate}
-  defp to_track_variants(_bitrate), do: %{}
 end

lib/membrane_rtc_engine/endpoints/webrtc_endpoint.ex

@@ -797,8 +797,7 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC do
   end
 
   defp handle_media_event(%{type: :track_variant_bitrates, data: data}, ctx, state) do
-    track_bitrates = Map.merge(state.track_id_to_bitrates[data.track_id], data.variant_bitrates)
-    state = put_in(state, [:track_id_to_bitrates, data.track_id], track_bitrates)
+    state = put_in(state, [:track_id_to_bitrates, data.track_id], data.variant_bitrates)
     msg = {:variant_bitrates, data.variant_bitrates}
 
     {forward({:track_sender, data.track_id}, msg, ctx), state}

test/membrane_rtc_engine/webrtc/media_event_test.exs

@@ -43,8 +43,8 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.MediaEventTest do
   describe "deserializing sdpOffer media event" do
     test "creates proper map when event is valid" do
       metadata = %{"track_id" => %{"abc" => "cba"}}
-      bitrates = %{"track_id" => %{"m" => 200}}
-      decoded_bitrates = %{"track_id" => %{medium: 200}}
+      bitrates = %{"track_id" => %{"m" => 200, "h" => 500, "l" => 100}}
+      decoded_bitrates = %{"track_id" => %{medium: 200, high: 500, low: 100}}
       mids = %{"5" => "track_id"}
       sdp = "mock_sdp"
 
@@ -108,8 +108,8 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.MediaEventTest do
   describe "deserializing trackVariantBitrates media event" do
     test "creates proper map when event is valid" do
       track_id = "track_id"
-      bitrates = %{"h" => 1000, "m" => 500}
-      decoded_bitrates = %{high: 1000, medium: 500}
+      bitrates = %{"h" => 1000, "m" => 500, "l" => 100}
+      decoded_bitrates = %{high: 1000, medium: 500, low: 100}
 
       raw_media_event =
         %{
@@ -146,7 +146,6 @@ defmodule Membrane.RTC.Engine.Endpoint.WebRTC.MediaEventTest do
             "type" => "trackVariantBitrates",
             "data" => %{
               "trackId" => "track_id"
-              # missing variantBitrates
             }
           }
         }