Protected streams report RTP messages directly to the FlexFec streams

webrtc/call/secondary_rtp_sinks_container.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_SECONDARY_RTP_SINKS_CONTAINER_H_
+#define WEBRTC_CALL_SECONDARY_RTP_SINKS_CONTAINER_H_
+
+namespace webrtc {
+
+class RtpPacketSinkInterface;
+
+// TODO(eladalon): !!! Find a better name?
+
+// By inheriting this class, a subclass of RtpPacketSinkInterface may provide
+// secondary sinks the ability to register with it, receiving OnRtpPacket()
+// called for them too over packets which get routed to the primary sink.
+// One usage for this is FlexFEC, which needs to see the packets of the
+// streams which it protects.
+class SecondaryRtpSinksContainer {

[danilchap, 2017/07/19 12:07:25]

I can see several implementation of this interface, but no users.
(i.e. whenever AddSecondarySink is called, full type is known)
How the interface is intended to be used?

[eladalon, 2017/07/21 14:42:08]

This TODO is about this:
  // TODO(eladalon): !!! Good? Bad? Do we want to have these functions
explicitly
  // part of the interface, without inheriting them, perhaps?
  #include "webrtc/call/secondary_rtp_sinks_container.h"
(FYI - "!!!" is my way of noting that I do not intend to land the CL until the
TODO is resolved within this CL, as opposed to normal TODOs, which I leave for
later handling.)

My intuition is that if any stream can be FlexFEC-protected, then there is a
concept of "protectable", which also in our implementation demands the concept
of "can register sub-sinks, some of which might be protectors." But this is
gut-feeling. I don't currently plan to have FlexFEC register itself with a list
of objects that implement this interface, for instance.

So wdyt?

+ public:
+  virtual ~SecondaryRtpSinksContainer() = default;
+
+  virtual void AddSecondarySink(RtpPacketSinkInterface* sink) = 0;
+  virtual void RemoveSecondarySink(const RtpPacketSinkInterface* sink) = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_CALL_SECONDARY_RTP_SINKS_CONTAINER_H_