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

@@ -252,14 +252,19 @@ func CodecPayloadType(codec webrtc.RTPCodecCapability) (webrtc.PayloadType, erro
 	}
 }
 
-func codecsFromName(name string) ([]webrtc.RTPCodecParameters, error) {
-	fb := []webrtc.RTCPFeedback{
+// 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:

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