Introduce RtpStreamReceiver and RtpStreamReceiverControllerInterface.

webrtc/call/rtp_transport_controller_receive_interface.h

+/*
+ *  Copyright (c) 2017 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.
+ */
+#ifndef WEBRTC_CALL_RTP_TRANSPORT_CONTROLLER_RECEIVE_INTERFACE_H_
+#define WEBRTC_CALL_RTP_TRANSPORT_CONTROLLER_RECEIVE_INTERFACE_H_
+
+#include <memory>
+
+#include "webrtc/call/rtp_demuxer.h"
+
+namespace webrtc {
+
+class RtpTransportReceiver {

[danilchap, 2017/05/23 12:53:09]

Add documentation for this class.
e.g. TODOs what it will be responsible for in the future.

[nisse-webrtc, 2017/05/29 13:35:50]

Done.

+ public:
+  virtual ~RtpTransportReceiver() {}
+};
+
+// This class acts as a factory for RtpTransportReceive objects.
+class RtpTransportControllerReceiveInterface {
+ public:
+  virtual ~RtpTransportControllerReceiveInterface() {}
+
+  virtual std::unique_ptr<RtpTransportReceiver> CreateReceiver(
+      uint32_t ssrc,
+      RtpPacketSinkInterface* sink) = 0;
+  // For registering additional sinks, needed for FlexFEC.
+  virtual void AddSink(uint32_t ssrc, RtpPacketSinkInterface* sink) = 0;

[danilchap, 2017/05/23 12:53:10]

shouldn't flexfec call CreateReceiver for each media stream it protect?

[nisse-webrtc, 2017/05/23 14:33:09]

I thought so too at first. But that will probably not work when the receiver
gets additional responsibilities, since
we don't want flexfec to instantiate any additional rtp receiver state for the
media streams it is protecting.

[danilchap, 2017/05/23 16:02:02]

another way: CreateReceiver might take not one ssrc, but array of them.
It need to take more complicated stream id anyway (that might be mid+rsid
instead of ssrc)

+  virtual size_t RemoveSink(const RtpPacketSinkInterface* sink) = 0;

[danilchap, 2017/05/23 12:53:10]

Should this function be in this interface?
May be RtpTransportReceiver should remove sinks through different interface.

[nisse-webrtc, 2017/05/23 14:33:09]

Only for symmetry with AddSink, which seems needed for flexfec.

+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_CALL_RTP_TRANSPORT_CONTROLLER_RECEIVE_INTERFACE_H_