MediaPipelineFilter.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: softtabstop=2:shiftwidth=2:expandtab

 * */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this file,

 * You can obtain one at http://mozilla.org/MPL/2.0/. */

// Original author: bcampen@mozilla.com

#ifndef mediapipelinefilter_h__

#define mediapipelinefilter_h__

#include <cstddef>

#include <stdint.h>

#include <string>

#include <set>

#include <vector>

#include "api/rtp_parameters.h"

#include "mozilla/Maybe.h"

namespace webrtc {

struct RTPHeader;

}  // namespace webrtc

namespace mozilla {

// TODO @@NG update documentation after initial review

// A class that handles the work of filtering RTP packets that arrive at a

// MediaPipeline. This is primarily important for the use of BUNDLE (ie;

// multiple m-lines share the same RTP stream). There are three ways that this

// can work;

//

// 1) In our SDP, we include a media-level extmap parameter with a unique

//    integer of our choosing, with the hope that the other side will include

//    this value in a header in the first few RTP packets it sends us. This

//    allows us to perform correlation in cases where the other side has not

//    informed us of the ssrcs it will be sending (either because it did not

//    include them in its SDP, or their SDP has not arrived yet)

//    and also gives us the opportunity to learn SSRCs from packets so adorned.

//

// 2) If the remote endpoint includes SSRC media-level attributes in its SDP,

//    we can simply use this information to populate the filter. The only

//    shortcoming here is when RTP packets arrive before the answer does. See

//    above.

//

// 3) As a fallback, we can try to use payload type IDs to perform correlation,

//    but only when the type id is unique to this media section.

//    This too allows us to learn about SSRCs (mostly useful for filtering

//    sender reports later).

class MediaPipelineFilter {

 public:

  MediaPipelineFilter() = default;

  explicit MediaPipelineFilter(

      const std::vector<webrtc::RtpExtension>& aExtMap);

  // Checks whether this packet passes the filter, possibly updating the filter

  // in the process (if the MID or payload types are used, they can teach

  // the filter about ssrcs)

  bool Filter(const webrtc::RTPHeader& header);

  void AddRemoteSSRC(uint32_t ssrc);

  void SetRemoteMediaStreamId(const Maybe<std::string>& aMid);

  // When a payload type id is unique to our media section, add it here.

  void AddUniqueReceivePT(uint8_t payload_type);

  void Update(const MediaPipelineFilter& filter_update);

  std::vector<webrtc::RtpExtension> GetExtmap() const { return mExtMap; }

 private:

  // The number of filters we manage here is quite small, so I am optimizing

  // for readability.

  std::set<uint32_t> remote_ssrc_set_;

  std::set<uint8_t> receive_payload_type_set_;

  Maybe<std::string> mRemoteMid;

  std::set<uint32_t> mRemoteMidBindings;

  // RID extension can be set by tests and is sticky, the rest of

  // the mapping is not.

  std::vector<webrtc::RtpExtension> mExtMap;

};

}  // end namespace mozilla

#endif  // mediapipelinefilter_h__