Use the configured remote ssrc instead of relying on the first received packet.

webrtc/video/rtp_video_stream_receiver.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 94 matching lines @@
                                 const WebRtcRTPHeader* rtp_header) override;
   // Implements RecoveredPacketReceiver.
   void OnRecoveredPacket(const uint8_t* packet, size_t packet_length) override;
 
   // Implements RtpFeedback.
   int32_t OnInitializeDecoder(int8_t payload_type,
                               const char payload_name[RTP_PAYLOAD_NAME_SIZE],
                               int frequency,
                               size_t channels,
                               uint32_t rate) override;
-  void OnIncomingSSRCChanged(uint32_t ssrc) override;
+  void OnIncomingSSRCChanged(uint32_t ssrc) override {}
   void OnIncomingCSRCChanged(uint32_t CSRC, bool added) override {}
 
   // Implements VCMFrameTypeCallback.
   int32_t RequestKeyFrame() override;
 
   bool IsUlpfecEnabled() const;
   bool IsRetransmissionsEnabled() const;
   // Don't use, still experimental.
   void RequestPacketRetransmit(const std::vector<uint16_t>& sequence_numbers);
 
@@ skipping 71 matching lines @@
   // Maps a payload type to a map of out-of-band supplied codec parameters.
   std::map<uint8_t, std::map<std::string, std::string>> pt_codec_params_;
   int16_t last_payload_type_ = -1;
 
   bool has_received_frame_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_VIDEO_RTP_VIDEO_STREAM_RECEIVER_H_