Don't honour NACKs if we're congested.

client.go

@@ -608,10 +608,14 @@ func rtcpDownListener(g *group, conn *downConnection, track *downTrack, s *webrt
 					}
 				}
 			case *rtcp.TransportLayerNack:
+				maxBitrate := track.maxBitrate.Get(msSinceEpoch())
+				bitrate := track.rate.Estimate()
+				if uint64(bitrate) < maxBitrate {
 					sendRecovery(p, track)
 				}
 			}
 		}
+	}
 }
 
 func trackKinds(down *downConnection) (audio bool, video bool) {
@@ -720,7 +724,9 @@ func sendRecovery(p *rtcp.TransportLayerNack, track *downTrack) {
 	for _, nack := range p.Nacks {
 		for _, seqno := range nack.PacketList() {
 			raw := track.remote.cache.Get(seqno)
-			if raw != nil {
+			if raw == nil {
+				continue
+			}
 			err := packet.Unmarshal(raw)
 			if err != nil {
 				continue
@@ -728,11 +734,11 @@ func sendRecovery(p *rtcp.TransportLayerNack, track *downTrack) {
 			err = track.track.WriteRTP(&packet)
 			if err != nil {
 				log.Printf("%v", err)
+				continue
 			}
 			track.rate.Add(uint32(len(raw)))
 		}
 	}
-	}
 }
 
 func countMediaStreams(data string) (int, error) {