Add RSID-based demuxing to RtpDemuxer

webrtc/call/rtp_demuxer.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_DEMUXER_H_
 #define WEBRTC_CALL_RTP_DEMUXER_H_
 
 #include <map>
+#include <set>
+#include <string>
 
 namespace webrtc {
 
 class RtpPacketReceived;
 
 // This class represents a receiver of an already parsed RTP packets.
 class RtpPacketSinkInterface {
  public:
   virtual ~RtpPacketSinkInterface() {}
   virtual void OnRtpPacket(const RtpPacketReceived& packet) = 0;
 };
 
 // This class represents the RTP demuxing, for a single RTP session (i.e., one
 // ssrc space, see RFC 7656). It isn't thread aware, leaving responsibility of
 // multithreading issues to the user of this class.
 // TODO(nisse): Should be extended to also do MID-based demux and payload-type
 // demux.
 class RtpDemuxer {
  public:
   RtpDemuxer();
   ~RtpDemuxer();
 
   // Registers a sink. The same sink can be registered for multiple ssrcs, and
   // the same ssrc can have multiple sinks. Null pointer is not allowed.
   void AddSink(uint32_t ssrc, RtpPacketSinkInterface* sink);
+
+  // Registers a sink's association to an RSID. Null pointer is not allowed.
+  void AddSink(const std::string& rsid, RtpPacketSinkInterface* sink);
+
   // Removes a sink. Returns deletion count (a sink may be registered
-  // for multiple ssrcs). Null pointer is not allowed.
+  // for multiple SSRCs and/or RSIDs). Null pointer is not allowed.
   size_t RemoveSink(const RtpPacketSinkInterface* sink);
 
   // Returns true if at least one matching sink was found, otherwise false.
   bool OnRtpPacket(const RtpPacketReceived& packet);
 
  private:
+  // Records a sink<->SSRC association. This can happen by explicit
+  // configuration by AddSink(ssrc...), or by inferred configuration from an
+  // RSID-based configuration which is resolved to an SSRC upon
+  // packet reception.
+  void RecordSsrcToSinkAssociation(uint32_t ssrc, RtpPacketSinkInterface* sink);
+
+  // When a new packet arrives, we attempt to resolve extra associations,
+  // such as which RSIDs are associated with which SSRCs.
+  void FindSsrcAssociations(const RtpPacketReceived& packet);
+
+  // This records the association SSRCs to sinks. Other associations, such
+  // as by RSID, also end up here once the RSID, etc., is resolved to an SSRC.
   std::multimap<uint32_t, RtpPacketSinkInterface*> sinks_;
+
+  // A sink may be associated with an RSID - RTP Stream ID. This tag has a
+  // one-to-one association with an SSRC, but that SSRC is not yet known.
+  // When it becomes known, the association of the sink to the RSID is deleted
+  // from this container, and moved into |sinks_|.
+  std::multimap<std::string, RtpPacketSinkInterface*> rsid_sinks_;
+
+  // Iterating over |rsid_sinks_| for each incoming and performing multiple
+  // string comparisons is of non-trivial cost. To avoid this cost, we only
+  // check RSIDs for the first packet on each incoming SSRC stream.
+  // (If RSID associations are added later, we check again.)
+  std::set<uint32_t> processed_ssrcs_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_CALL_RTP_DEMUXER_H_