Make RTX pt/apt reconfigurable by calling WebRtcVideoChannel2::SetRecvParameters.

webrtc/video/rtp_stream_receiver.cc

Index: webrtc/video/rtp_stream_receiver.cc
diff --git a/webrtc/video/rtp_stream_receiver.cc b/webrtc/video/rtp_stream_receiver.cc
index d2360858729993b3432006b746bc0c54516d729b..d4755d6805c374a718406b8caccf84649402694d 100644
--- a/webrtc/video/rtp_stream_receiver.cc
+++ b/webrtc/video/rtp_stream_receiver.cc
@@ -160,14 +160,13 @@ RtpStreamReceiver::RtpStreamReceiver(
                                            : kDefaultMaxReorderingThreshold;
   rtp_receive_statistics_->SetMaxReorderingThreshold(max_reordering_threshold);
 
-  // TODO(pbos): Support multiple RTX, per video payload.
-  for (const auto& kv : config_.rtp.rtx) {
-    RTC_DCHECK(kv.second.ssrc != 0);
-    RTC_DCHECK(kv.second.payload_type != 0);
-
-    rtp_payload_registry_.SetRtxSsrc(kv.second.ssrc);
-    rtp_payload_registry_.SetRtxPayloadType(kv.second.payload_type,
-                                            kv.first);
+  if (config_.rtp.rtx_ssrc) {

[brandtr, 2017/01/20 14:49:23]

Both an SSRC and the pt/apt mapping is needed to decode received RTX packets.

+    rtp_payload_registry_.SetRtxSsrc(config_.rtp.rtx_ssrc);
+
+    for (const auto& kv : config_.rtp.rtx_payload_types) {
+      RTC_DCHECK(kv.second != 0);
+      rtp_payload_registry_.SetRtxPayloadType(kv.second, kv.first);
+    }
   }
 
   if (IsUlpfecEnabled()) {