Fix examples sometimes not loading in Chromium (#133)

examples/echo/lib/echo/peer_handler.ex

@@ -128,8 +128,19 @@ defmodule Echo.PeerHandler do
     {:ok, state}
   end
 
-  defp handle_webrtc_msg({:rtcp, _packets}, state) do
-    # do something with RTCP packets
+  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 ->
+          Logger.info("Received keyframe request. Sending PLI.")
+          :ok = PeerConnection.send_pli(state.peer_connection, state.in_video_track_id, "h")
+
+        _other ->
+          # do something with other RTCP packets
+          :ok
+      end
+    end
+
     {:ok, state}
   end
 

examples/send_from_file/README.md

@@ -7,10 +7,17 @@ While in `examples/send_from_file` directory
 1. Generate media files
 
 ```shell
-ffmpeg -f lavfi -i testsrc=duration=5:size=640x480:rate=30 video.ivf
+ffmpeg -f lavfi -i testsrc=duration=5:size=640x480:rate=30 -g 60 video.ivf
 ffmpeg -f lavfi -i sine=frequency=420:duration=5 -c:a libopus audio.ogg
 ```
 
+> [!NOTE]
+> Option `-g` defines a GOP size i.e. how frequently we will generate a new keyframe.
+> Our framerate is 30, so we set the GOP to 60 to have a new keyframe every two seconds.
+> This is to make sure, that even if something goes really badly and your keyframe is dropped
+> (e.g. there is a bug in a web browser, or something strange happend on your network interface), 
+> a browser, in the worst case scenario, will get a new one in two seconds.
+
 You may use your own files, if they meet the requirements:
 * for video, it must be IVF in 30 FPS,
 * for audio, it must be Ogg with a single Opus stream.