media/base/stream_params.h - src - Git at Google

 /*
  *  Copyright (c) 2011 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.
  */

 // This file contains structures for describing SSRCs from a media source such
 // as a MediaStreamTrack when it is sent across an RTP session. Multiple media
 // sources may be sent across the same RTP session, each of them will be
 // described by one StreamParams object
 // SsrcGroup is used to describe the relationship between the SSRCs that
 // are used for this media source.
 // E.x: Consider a source that is sent as 3 simulcast streams
 // Let the simulcast elements have SSRC 10, 20, 30.
 // Let each simulcast element use FEC and let the protection packets have
 // SSRC 11,21,31.
 // To describe this 4 SsrcGroups are needed,
 // StreamParams would then contain ssrc = {10,11,20,21,30,31} and
 // ssrc_groups = {{SIM,{10,20,30}, {FEC,{10,11}, {FEC, {20,21}, {FEC {30,31}}}
 // Please see RFC 5576.
 // A spec-compliant way to achieve this is to use RIDs and Simulcast attribute
 // instead of the ssrc-group. In this method, the StreamParam object will
 // have multiple RidDescriptions, each corresponding to a simulcast layer
 // and the media section will have a simulcast attribute that indicates
 // that these layers are for the same source. This also removes the extra
 // lines for redundancy streams, as the same RIDs appear in the redundancy
 // packets.
 // Note: in the spec compliant simulcast scenario, some of the RIDs might be
 // alternatives for one another (such as different encodings for same data).
 // In the context of the StreamParams class, the notion of alternatives does
 // not exist and all the RIDs will describe different layers of the same source.
 // When the StreamParams class is used to configure the media engine, simulcast
 // considerations will be used to remove the alternative layers outside of this
 // class.
 // As an example, let the simulcast layers have RID 10, 20, 30.
 // StreamParams would contain rid = { 10, 20, 30 }.
 // MediaSection would contain SimulcastDescription specifying these rids.
 // a=simulcast:send 10;20;30 (or a=simulcast:send 10,20;30 or similar).
 // See https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13
 // and https://tools.ietf.org/html/draft-ietf-mmusic-rid-15.

 #ifndef MEDIA_BASE_STREAM_PARAMS_H_
 #define MEDIA_BASE_STREAM_PARAMS_H_

 #include <stddef.h>
 #include <cstdint>
 #include <string>
 #include <vector>

 #include "absl/algorithm/container.h"
 #include "media/base/rid_description.h"
 #include "rtc_base/constructor_magic.h"
 #include "rtc_base/unique_id_generator.h"

 namespace cricket {

 extern const char kFecSsrcGroupSemantics[];
 extern const char kFecFrSsrcGroupSemantics[];
 extern const char kFidSsrcGroupSemantics[];
 extern const char kSimSsrcGroupSemantics[];

 struct SsrcGroup {
   SsrcGroup(const std::string& usage, const std::vector<uint32_t>& ssrcs);
   SsrcGroup(const SsrcGroup&);
   SsrcGroup(SsrcGroup&&);
   ~SsrcGroup();
   SsrcGroup& operator=(const SsrcGroup&);
   SsrcGroup& operator=(SsrcGroup&&);

   bool operator==(const SsrcGroup& other) const {
     return (semantics == other.semantics && ssrcs == other.ssrcs);
   }
   bool operator!=(const SsrcGroup& other) const { return !(*this == other); }

   bool has_semantics(const std::string& semantics) const;

   std::string ToString() const;

   std::string semantics;        // e.g FIX, FEC, SIM.
   std::vector<uint32_t> ssrcs;  // SSRCs of this type.
 };

 // StreamParams is used to represent a sender/track in a SessionDescription.
 // In Plan B, this means that multiple StreamParams can exist within one
 // MediaContentDescription, while in UnifiedPlan this means that there is one
 // StreamParams per MediaContentDescription.
 struct StreamParams {
   StreamParams();
   StreamParams(const StreamParams&);
   StreamParams(StreamParams&&);
   ~StreamParams();
   StreamParams& operator=(const StreamParams&);
   StreamParams& operator=(StreamParams&&);

   static StreamParams CreateLegacy(uint32_t ssrc) {
     StreamParams stream;
     stream.ssrcs.push_back(ssrc);
     return stream;
   }

   bool operator==(const StreamParams& other) const;
   bool operator!=(const StreamParams& other) const { return !(*this == other); }

   uint32_t first_ssrc() const {
     if (ssrcs.empty()) {
       return 0;
     }

     return ssrcs[0];
   }
   bool has_ssrcs() const { return !ssrcs.empty(); }
   bool has_ssrc(uint32_t ssrc) const {
     return absl::c_linear_search(ssrcs, ssrc);
   }
   void add_ssrc(uint32_t ssrc) { ssrcs.push_back(ssrc); }
   bool has_ssrc_groups() const { return !ssrc_groups.empty(); }
   bool has_ssrc_group(const std::string& semantics) const {
     return (get_ssrc_group(semantics) != NULL);
   }
   const SsrcGroup* get_ssrc_group(const std::string& semantics) const {
     for (std::vector<SsrcGroup>::const_iterator it = ssrc_groups.begin();
          it != ssrc_groups.end(); ++it) {
       if (it->has_semantics(semantics)) {
         return &(*it);
       }
     }
     return NULL;
   }

   // Convenience function to add an FID ssrc for a primary_ssrc
   // that's already been added.
   bool AddFidSsrc(uint32_t primary_ssrc, uint32_t fid_ssrc) {
     return AddSecondarySsrc(kFidSsrcGroupSemantics, primary_ssrc, fid_ssrc);
   }

   // Convenience function to lookup the FID ssrc for a primary_ssrc.
   // Returns false if primary_ssrc not found or FID not defined for it.
   bool GetFidSsrc(uint32_t primary_ssrc, uint32_t* fid_ssrc) const {
     return GetSecondarySsrc(kFidSsrcGroupSemantics, primary_ssrc, fid_ssrc);
   }

   // Convenience function to add an FEC-FR ssrc for a primary_ssrc
   // that's already been added.
   bool AddFecFrSsrc(uint32_t primary_ssrc, uint32_t fecfr_ssrc) {
     return AddSecondarySsrc(kFecFrSsrcGroupSemantics, primary_ssrc, fecfr_ssrc);
   }

   // Convenience function to lookup the FEC-FR ssrc for a primary_ssrc.
   // Returns false if primary_ssrc not found or FEC-FR not defined for it.
   bool GetFecFrSsrc(uint32_t primary_ssrc, uint32_t* fecfr_ssrc) const {
     return GetSecondarySsrc(kFecFrSsrcGroupSemantics, primary_ssrc, fecfr_ssrc);
   }

   // Convenience function to populate the StreamParams with the requested number
   // of SSRCs along with accompanying FID and FEC-FR ssrcs if requested.
   // SSRCs are generated using the given generator.
   void GenerateSsrcs(int num_layers,
                      bool generate_fid,
                      bool generate_fec_fr,
                      rtc::UniqueRandomIdGenerator* ssrc_generator);

   // Convenience to get all the SIM SSRCs if there are SIM ssrcs, or
   // the first SSRC otherwise.
   void GetPrimarySsrcs(std::vector<uint32_t>* ssrcs) const;

   // Convenience to get all the FID SSRCs for the given primary ssrcs.
   // If a given primary SSRC does not have a FID SSRC, the list of FID
   // SSRCS will be smaller than the list of primary SSRCs.
   void GetFidSsrcs(const std::vector<uint32_t>& primary_ssrcs,
                    std::vector<uint32_t>* fid_ssrcs) const;

   // Stream ids serialized to SDP.
   std::vector<std::string> stream_ids() const;
   void set_stream_ids(const std::vector<std::string>& stream_ids);

   // Returns the first stream id or "" if none exist. This method exists only
   // as temporary backwards compatibility with the old sync_label.
   std::string first_stream_id() const;

   std::string ToString() const;

   // Resource of the MUC jid of the participant of with this stream.
   // For 1:1 calls, should be left empty (which means remote streams
   // and local streams should not be mixed together). This is not used
   // internally and should be deprecated.
   std::string groupid;
   // A unique identifier of the StreamParams object. When the SDP is created,
   // this comes from the track ID of the sender that the StreamParams object
   // is associated with.
   std::string id;
   // There may be no SSRCs stored in unsignaled case when stream_ids are
   // signaled with a=msid lines.
   std::vector<uint32_t> ssrcs;         // All SSRCs for this source
   std::vector<SsrcGroup> ssrc_groups;  // e.g. FID, FEC, SIM
   std::string cname;                   // RTCP CNAME

   // RID functionality according to
   // https://tools.ietf.org/html/draft-ietf-mmusic-rid-15
   // Each layer can be represented by a RID identifier and can also have
   // restrictions (such as max-width, max-height, etc.)
   // If the track has multiple layers (ex. Simulcast), each layer will be
   // represented by a RID.
   bool has_rids() const { return !rids_.empty(); }
   const std::vector<RidDescription>& rids() const { return rids_; }
   void set_rids(const std::vector<RidDescription>& rids) { rids_ = rids; }

  private:
   bool AddSecondarySsrc(const std::string& semantics,
                         uint32_t primary_ssrc,
                         uint32_t secondary_ssrc);
   bool GetSecondarySsrc(const std::string& semantics,
                         uint32_t primary_ssrc,
                         uint32_t* secondary_ssrc) const;

   // The stream IDs of the sender that the StreamParams object is associated
   // with. In Plan B this should always be size of 1, while in Unified Plan this
   // could be none or multiple stream IDs.
   std::vector<std::string> stream_ids_;

   std::vector<RidDescription> rids_;
 };

 // A Stream can be selected by either groupid+id or ssrc.
 struct StreamSelector {
   explicit StreamSelector(uint32_t ssrc) : ssrc(ssrc) {}

   StreamSelector(const std::string& groupid, const std::string& streamid)
       : ssrc(0), groupid(groupid), streamid(streamid) {}

   explicit StreamSelector(const std::string& streamid)
       : ssrc(0), streamid(streamid) {}

   bool Matches(const StreamParams& stream) const {
     if (ssrc == 0) {
       return stream.groupid == groupid && stream.id == streamid;
     } else {
       return stream.has_ssrc(ssrc);
     }
   }

   uint32_t ssrc;
   std::string groupid;
   std::string streamid;
 };

 typedef std::vector<StreamParams> StreamParamsVec;

 template <class Condition>
 const StreamParams* GetStream(const StreamParamsVec& streams,
                               Condition condition) {
   auto found = absl::c_find_if(streams, condition);
   return found == streams.end() ? nullptr : &(*found);
 }

 template <class Condition>
 StreamParams* GetStream(StreamParamsVec& streams, Condition condition) {
   auto found = absl::c_find_if(streams, condition);
   return found == streams.end() ? nullptr : &(*found);
 }

 inline bool HasStreamWithNoSsrcs(const StreamParamsVec& streams) {
   return GetStream(streams,
                    [](const StreamParams& sp) { return !sp.has_ssrcs(); });
 }

 inline const StreamParams* GetStreamBySsrc(const StreamParamsVec& streams,
                                            uint32_t ssrc) {
   return GetStream(
       streams, [&ssrc](const StreamParams& sp) { return sp.has_ssrc(ssrc); });
 }

 inline const StreamParams* GetStreamByIds(const StreamParamsVec& streams,
                                           const std::string& groupid,
                                           const std::string& id) {
   return GetStream(streams, [&groupid, &id](const StreamParams& sp) {
     return sp.groupid == groupid && sp.id == id;
   });
 }

 inline StreamParams* GetStreamByIds(StreamParamsVec& streams,
                                     const std::string& groupid,
                                     const std::string& id) {
   return GetStream(streams, [&groupid, &id](const StreamParams& sp) {
     return sp.groupid == groupid && sp.id == id;
   });
 }

 inline const StreamParams* GetStream(const StreamParamsVec& streams,
                                      const StreamSelector& selector) {
   return GetStream(streams, [&selector](const StreamParams& sp) {
     return selector.Matches(sp);
   });
 }

 template <class Condition>
 bool RemoveStream(StreamParamsVec* streams, Condition condition) {
   auto iter(std::remove_if(streams->begin(), streams->end(), condition));
   if (iter == streams->end())
     return false;
   streams->erase(iter, streams->end());
   return true;
 }

 // Removes the stream from streams. Returns true if a stream is
 // found and removed.
 inline bool RemoveStream(StreamParamsVec* streams,
                          const StreamSelector& selector) {
   return RemoveStream(streams, [&selector](const StreamParams& sp) {
     return selector.Matches(sp);
   });
 }
 inline bool RemoveStreamBySsrc(StreamParamsVec* streams, uint32_t ssrc) {
   return RemoveStream(
       streams, [&ssrc](const StreamParams& sp) { return sp.has_ssrc(ssrc); });
 }
 inline bool RemoveStreamByIds(StreamParamsVec* streams,
                               const std::string& groupid,
                               const std::string& id) {
   return RemoveStream(streams, [&groupid, &id](const StreamParams& sp) {
     return sp.groupid == groupid && sp.id == id;
   });
 }

 }  // namespace cricket

 #endif  // MEDIA_BASE_STREAM_PARAMS_H_
	/*
	* Copyright (c) 2011 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.
	*/

	// This file contains structures for describing SSRCs from a media source such
	// as a MediaStreamTrack when it is sent across an RTP session. Multiple media
	// sources may be sent across the same RTP session, each of them will be
	// described by one StreamParams object
	// SsrcGroup is used to describe the relationship between the SSRCs that
	// are used for this media source.
	// E.x: Consider a source that is sent as 3 simulcast streams
	// Let the simulcast elements have SSRC 10, 20, 30.
	// Let each simulcast element use FEC and let the protection packets have
	// SSRC 11,21,31.
	// To describe this 4 SsrcGroups are needed,
	// StreamParams would then contain ssrc = {10,11,20,21,30,31} and
	// ssrc_groups = {{SIM,{10,20,30}, {FEC,{10,11}, {FEC, {20,21}, {FEC {30,31}}}
	// Please see RFC 5576.
	// A spec-compliant way to achieve this is to use RIDs and Simulcast attribute
	// instead of the ssrc-group. In this method, the StreamParam object will
	// have multiple RidDescriptions, each corresponding to a simulcast layer
	// and the media section will have a simulcast attribute that indicates
	// that these layers are for the same source. This also removes the extra
	// lines for redundancy streams, as the same RIDs appear in the redundancy
	// packets.
	// Note: in the spec compliant simulcast scenario, some of the RIDs might be
	// alternatives for one another (such as different encodings for same data).
	// In the context of the StreamParams class, the notion of alternatives does
	// not exist and all the RIDs will describe different layers of the same source.
	// When the StreamParams class is used to configure the media engine, simulcast
	// considerations will be used to remove the alternative layers outside of this
	// class.
	// As an example, let the simulcast layers have RID 10, 20, 30.
	// StreamParams would contain rid = { 10, 20, 30 }.
	// MediaSection would contain SimulcastDescription specifying these rids.
	// a=simulcast:send 10;20;30 (or a=simulcast:send 10,20;30 or similar).
	// See https://tools.ietf.org/html/draft-ietf-mmusic-sdp-simulcast-13
	// and https://tools.ietf.org/html/draft-ietf-mmusic-rid-15.

	#ifndef MEDIA_BASE_STREAM_PARAMS_H_
	#define MEDIA_BASE_STREAM_PARAMS_H_

	#include <stddef.h>
	#include <cstdint>
	#include <string>
	#include <vector>

	#include "absl/algorithm/container.h"
	#include "media/base/rid_description.h"
	#include "rtc_base/constructor_magic.h"
	#include "rtc_base/unique_id_generator.h"

	namespace cricket {

	extern const char kFecSsrcGroupSemantics[];
	extern const char kFecFrSsrcGroupSemantics[];
	extern const char kFidSsrcGroupSemantics[];
	extern const char kSimSsrcGroupSemantics[];

	struct SsrcGroup {
	SsrcGroup(const std::string& usage, const std::vector<uint32_t>& ssrcs);
	SsrcGroup(const SsrcGroup&);
	SsrcGroup(SsrcGroup&&);
	~SsrcGroup();
	SsrcGroup& operator=(const SsrcGroup&);
	SsrcGroup& operator=(SsrcGroup&&);

	bool operator==(const SsrcGroup& other) const {
	return (semantics == other.semantics && ssrcs == other.ssrcs);
	}
	bool operator!=(const SsrcGroup& other) const { return !(*this == other); }

	bool has_semantics(const std::string& semantics) const;

	std::string ToString() const;

	std::string semantics; // e.g FIX, FEC, SIM.
	std::vector<uint32_t> ssrcs; // SSRCs of this type.
	};

	// StreamParams is used to represent a sender/track in a SessionDescription.
	// In Plan B, this means that multiple StreamParams can exist within one
	// MediaContentDescription, while in UnifiedPlan this means that there is one
	// StreamParams per MediaContentDescription.
	struct StreamParams {
	StreamParams();
	StreamParams(const StreamParams&);
	StreamParams(StreamParams&&);
	~StreamParams();
	StreamParams& operator=(const StreamParams&);
	StreamParams& operator=(StreamParams&&);

	static StreamParams CreateLegacy(uint32_t ssrc) {
	StreamParams stream;
	stream.ssrcs.push_back(ssrc);
	return stream;
	}

	bool operator==(const StreamParams& other) const;
	bool operator!=(const StreamParams& other) const { return !(*this == other); }

	uint32_t first_ssrc() const {
	if (ssrcs.empty()) {
	return 0;
	}

	return ssrcs[0];
	}
	bool has_ssrcs() const { return !ssrcs.empty(); }
	bool has_ssrc(uint32_t ssrc) const {
	return absl::c_linear_search(ssrcs, ssrc);
	}
	void add_ssrc(uint32_t ssrc) { ssrcs.push_back(ssrc); }
	bool has_ssrc_groups() const { return !ssrc_groups.empty(); }
	bool has_ssrc_group(const std::string& semantics) const {
	return (get_ssrc_group(semantics) != NULL);
	}
	const SsrcGroup* get_ssrc_group(const std::string& semantics) const {
	for (std::vector<SsrcGroup>::const_iterator it = ssrc_groups.begin();
	it != ssrc_groups.end(); ++it) {
	if (it->has_semantics(semantics)) {
	return &(*it);
	}
	}
	return NULL;
	}

	// Convenience function to add an FID ssrc for a primary_ssrc
	// that's already been added.
	bool AddFidSsrc(uint32_t primary_ssrc, uint32_t fid_ssrc) {
	return AddSecondarySsrc(kFidSsrcGroupSemantics, primary_ssrc, fid_ssrc);
	}

	// Convenience function to lookup the FID ssrc for a primary_ssrc.
	// Returns false if primary_ssrc not found or FID not defined for it.
	bool GetFidSsrc(uint32_t primary_ssrc, uint32_t* fid_ssrc) const {
	return GetSecondarySsrc(kFidSsrcGroupSemantics, primary_ssrc, fid_ssrc);
	}

	// Convenience function to add an FEC-FR ssrc for a primary_ssrc
	// that's already been added.
	bool AddFecFrSsrc(uint32_t primary_ssrc, uint32_t fecfr_ssrc) {
	return AddSecondarySsrc(kFecFrSsrcGroupSemantics, primary_ssrc, fecfr_ssrc);
	}

	// Convenience function to lookup the FEC-FR ssrc for a primary_ssrc.
	// Returns false if primary_ssrc not found or FEC-FR not defined for it.
	bool GetFecFrSsrc(uint32_t primary_ssrc, uint32_t* fecfr_ssrc) const {
	return GetSecondarySsrc(kFecFrSsrcGroupSemantics, primary_ssrc, fecfr_ssrc);
	}

	// Convenience function to populate the StreamParams with the requested number
	// of SSRCs along with accompanying FID and FEC-FR ssrcs if requested.
	// SSRCs are generated using the given generator.
	void GenerateSsrcs(int num_layers,
	bool generate_fid,
	bool generate_fec_fr,
	rtc::UniqueRandomIdGenerator* ssrc_generator);

	// Convenience to get all the SIM SSRCs if there are SIM ssrcs, or
	// the first SSRC otherwise.
	void GetPrimarySsrcs(std::vector<uint32_t>* ssrcs) const;

	// Convenience to get all the FID SSRCs for the given primary ssrcs.
	// If a given primary SSRC does not have a FID SSRC, the list of FID
	// SSRCS will be smaller than the list of primary SSRCs.
	void GetFidSsrcs(const std::vector<uint32_t>& primary_ssrcs,
	std::vector<uint32_t>* fid_ssrcs) const;

	// Stream ids serialized to SDP.
	std::vector<std::string> stream_ids() const;
	void set_stream_ids(const std::vector<std::string>& stream_ids);

	// Returns the first stream id or "" if none exist. This method exists only
	// as temporary backwards compatibility with the old sync_label.
	std::string first_stream_id() const;

	std::string ToString() const;

	// Resource of the MUC jid of the participant of with this stream.
	// For 1:1 calls, should be left empty (which means remote streams
	// and local streams should not be mixed together). This is not used
	// internally and should be deprecated.
	std::string groupid;
	// A unique identifier of the StreamParams object. When the SDP is created,
	// this comes from the track ID of the sender that the StreamParams object
	// is associated with.
	std::string id;
	// There may be no SSRCs stored in unsignaled case when stream_ids are
	// signaled with a=msid lines.
	std::vector<uint32_t> ssrcs; // All SSRCs for this source
	std::vector<SsrcGroup> ssrc_groups; // e.g. FID, FEC, SIM
	std::string cname; // RTCP CNAME

	// RID functionality according to
	// https://tools.ietf.org/html/draft-ietf-mmusic-rid-15
	// Each layer can be represented by a RID identifier and can also have
	// restrictions (such as max-width, max-height, etc.)
	// If the track has multiple layers (ex. Simulcast), each layer will be
	// represented by a RID.
	bool has_rids() const { return !rids_.empty(); }
	const std::vector<RidDescription>& rids() const { return rids_; }
	void set_rids(const std::vector<RidDescription>& rids) { rids_ = rids; }

	private:
	bool AddSecondarySsrc(const std::string& semantics,
	uint32_t primary_ssrc,
	uint32_t secondary_ssrc);
	bool GetSecondarySsrc(const std::string& semantics,
	uint32_t primary_ssrc,
	uint32_t* secondary_ssrc) const;

	// The stream IDs of the sender that the StreamParams object is associated
	// with. In Plan B this should always be size of 1, while in Unified Plan this
	// could be none or multiple stream IDs.
	std::vector<std::string> stream_ids_;

	std::vector<RidDescription> rids_;
	};

	// A Stream can be selected by either groupid+id or ssrc.
	struct StreamSelector {
	explicit StreamSelector(uint32_t ssrc) : ssrc(ssrc) {}

	StreamSelector(const std::string& groupid, const std::string& streamid)
	: ssrc(0), groupid(groupid), streamid(streamid) {}

	explicit StreamSelector(const std::string& streamid)
	: ssrc(0), streamid(streamid) {}

	bool Matches(const StreamParams& stream) const {
	if (ssrc == 0) {
	return stream.groupid == groupid && stream.id == streamid;
	} else {
	return stream.has_ssrc(ssrc);
	}
	}

	uint32_t ssrc;
	std::string groupid;
	std::string streamid;
	};

	typedef std::vector<StreamParams> StreamParamsVec;

	template <class Condition>
	const StreamParams* GetStream(const StreamParamsVec& streams,
	Condition condition) {
	auto found = absl::c_find_if(streams, condition);
	return found == streams.end() ? nullptr : &(*found);
	}

	template <class Condition>
	StreamParams* GetStream(StreamParamsVec& streams, Condition condition) {
	auto found = absl::c_find_if(streams, condition);
	return found == streams.end() ? nullptr : &(*found);
	}

	inline bool HasStreamWithNoSsrcs(const StreamParamsVec& streams) {
	return GetStream(streams,
	[](const StreamParams& sp) { return !sp.has_ssrcs(); });
	}

	inline const StreamParams* GetStreamBySsrc(const StreamParamsVec& streams,
	uint32_t ssrc) {
	return GetStream(
	streams, [&ssrc](const StreamParams& sp) { return sp.has_ssrc(ssrc); });
	}

	inline const StreamParams* GetStreamByIds(const StreamParamsVec& streams,
	const std::string& groupid,
	const std::string& id) {
	return GetStream(streams, [&groupid, &id](const StreamParams& sp) {
	return sp.groupid == groupid && sp.id == id;
	});
	}

	inline StreamParams* GetStreamByIds(StreamParamsVec& streams,
	const std::string& groupid,
	const std::string& id) {
	return GetStream(streams, [&groupid, &id](const StreamParams& sp) {
	return sp.groupid == groupid && sp.id == id;
	});
	}

	inline const StreamParams* GetStream(const StreamParamsVec& streams,
	const StreamSelector& selector) {
	return GetStream(streams, [&selector](const StreamParams& sp) {
	return selector.Matches(sp);
	});
	}

	template <class Condition>
	bool RemoveStream(StreamParamsVec* streams, Condition condition) {
	auto iter(std::remove_if(streams->begin(), streams->end(), condition));
	if (iter == streams->end())
	return false;
	streams->erase(iter, streams->end());
	return true;
	}

	// Removes the stream from streams. Returns true if a stream is
	// found and removed.
	inline bool RemoveStream(StreamParamsVec* streams,
	const StreamSelector& selector) {
	return RemoveStream(streams, [&selector](const StreamParams& sp) {
	return selector.Matches(sp);
	});
	}
	inline bool RemoveStreamBySsrc(StreamParamsVec* streams, uint32_t ssrc) {
	return RemoveStream(
	streams, [&ssrc](const StreamParams& sp) { return sp.has_ssrc(ssrc); });
	}
	inline bool RemoveStreamByIds(StreamParamsVec* streams,
	const std::string& groupid,
	const std::string& id) {
	return RemoveStream(streams, [&groupid, &id](const StreamParams& sp) {
	return sp.groupid == groupid && sp.id == id;
	});
	}

	} // namespace cricket

	#endif // MEDIA_BASE_STREAM_PARAMS_H_