From ef0201c94d8eff01ea2f9ae7e0cc3ffe1fc40d85 Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Sat, 30 Nov 2024 17:55:24 +0100
Subject: [PATCH] Replace RTCPFeedback in down tracks.

We used to copy the RTCPFeeback field from the up track.  It is
more correct to regenerate it with the exact feedback types
that we expect.
---
 group/group.go       | 37 +++++++++++++++++++++----------------
 rtpconn/webclient.go | 13 +++++++++++--
 2 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/group/group.go b/group/group.go
index 2a9b1f9..1bdd82e 100644
--- a/group/group.go
+++ b/group/group.go
@@ -252,14 +252,19 @@ func CodecPayloadType(codec webrtc.RTPCodecCapability) (webrtc.PayloadType, erro
 	}
 }
 
-func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
-	fb := []webrtc.RTCPFeedback{
-		{"goog-remb", ""},
-		{"nack", ""},
-		{"nack", "pli"},
-		{"ccm", "fir"},
-	}
+// VideoRTCPFeedback are the RTCP feedback types that we expect for video
+// tracks.
+var VideoRTCPFeedback = []webrtc.RTCPFeedback{
+	{"goog-remb", ""},
+	{"nack", ""},
+	{"nack", "pli"},
+	{"ccm", "fir"},
+}
 
+// AudioRTCPFeedback is like VideoRTCPFeedback but for audio tracks.
+var AudioRTCPFeedback = []webrtc.RTCPFeedback(nil)
+
+func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 	var codecs []webrtc.RTPCodecCapability
 
 	switch name {
@@ -268,7 +273,7 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"video/VP8", 90000, 0,
 				"",
-				fb,
+				VideoRTCPFeedback,
 			},
 		}
 	case "vp9":
@@ -276,12 +281,12 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"video/VP9", 90000, 0,
 				"profile-id=0",
-				fb,
+				VideoRTCPFeedback,
 			},
 			{
 				"video/VP9", 90000, 0,
 				"profile-id=2",
-				fb,
+				VideoRTCPFeedback,
 			},
 		}
 	case "av1":
@@ -289,7 +294,7 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"video/AV1", 90000, 0,
 				"",
-				fb,
+				VideoRTCPFeedback,
 			},
 		}
 	case "h264":
@@ -297,7 +302,7 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"video/H264", 90000, 0,
 				"level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f",
-				fb,
+				VideoRTCPFeedback,
 			},
 		}
 	case "opus":
@@ -305,7 +310,7 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"audio/opus", 48000, 2,
 				"minptime=10;useinbandfec=1;stereo=1;sprop-stereo=1",
-				nil,
+				AudioRTCPFeedback,
 			},
 		}
 	case "g722":
@@ -313,7 +318,7 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"audio/G722", 8000, 1,
 				"",
-				nil,
+				AudioRTCPFeedback,
 			},
 		}
 	case "pcmu":
@@ -321,7 +326,7 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"audio/PCMU", 8000, 1,
 				"",
-				nil,
+				AudioRTCPFeedback,
 			},
 		}
 	case "pcma":
@@ -329,7 +334,7 @@ func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
 			{
 				"audio/PCMU", 8000, 1,
 				"",
-				nil,
+				AudioRTCPFeedback,
 			},
 		}
 	default:
diff --git a/rtpconn/webclient.go b/rtpconn/webclient.go
index 5e6567c..2730031 100644
--- a/rtpconn/webclient.go
+++ b/rtpconn/webclient.go
@@ -9,6 +9,7 @@ import (
 	"log"
 	"net"
 	"os"
+	"strings"
 	"sync"
 	"time"
 
@@ -381,8 +382,16 @@ func addDownTrackUnlocked(conn *rtpDownConnection, remoteTrack *rtpUpTrack) erro
 		msid = "dummy"
 	}
 
+	// replace the RTCP feedback types with the ones we understand
+	remoteCodec := remoteTrack.Codec()
+	if strings.HasPrefix(strings.ToLower(remoteCodec.MimeType), "video/") {
+		remoteCodec.RTCPFeedback = group.VideoRTCPFeedback
+	} else {
+		remoteCodec.RTCPFeedback = group.AudioRTCPFeedback
+	}
+
 	local, err := webrtc.NewTrackLocalStaticRTP(
-		remoteTrack.Codec(), id, msid,
+		remoteCodec, id, msid,
 	)
 	if err != nil {
 		return err
@@ -1660,7 +1669,7 @@ func handleClientMessage(c *webClient, m clientMessage) error {
 			m := clientMessage{
 				Type:       "usermessage",
 				Kind:       "clearchat",
-				Value:       m.Value,
+				Value:      m.Value,
 				Privileged: true,
 			}
 			err := broadcast(g.GetClients(nil), m)