text: /*
   *  Copyright 2012 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 interfaces for MediaStream, MediaTrack and MediaSource.
  // These interfaces are used for implementing MediaStream and MediaTrack as
  // defined in http://dev.w3.org/2011/webrtc/editor/webrtc.html#stream-api. These
  // interfaces must be used only with PeerConnection. PeerConnectionManager
  // interface provides the factory methods to create MediaStream and MediaTracks.
  
  #ifndef API_MEDIASTREAMINTERFACE_H_
  #define API_MEDIASTREAMINTERFACE_H_
  
  #include <stddef.h>
  
  #include <string>
  #include <vector>
  
  #include "api/optional.h"
  #include "api/video/video_frame.h"
  // TODO(zhihuang): Remove unrelated headers once downstream applications stop
  // relying on them; they were previously transitively included by
  // mediachannel.h, which is no longer a dependency of this file.
  #include "api/videosinkinterface.h"
  #include "api/videosourceinterface.h"
  #include "modules/audio_processing/include/audio_processing_statistics.h"
  #include "rtc_base/ratetracker.h"
  #include "rtc_base/refcount.h"
  #include "rtc_base/scoped_ref_ptr.h"
  #include "rtc_base/thread.h"
  #include "rtc_base/timeutils.h"
  
  namespace webrtc {
  
  // Generic observer interface.
  class ObserverInterface {
   public:
    virtual void OnChanged() = 0;
  
   protected:
    virtual ~ObserverInterface() {}
  };
  
  class NotifierInterface {
   public:
    virtual void RegisterObserver(ObserverInterface* observer) = 0;
    virtual void UnregisterObserver(ObserverInterface* observer) = 0;
  
    virtual ~NotifierInterface() {}
  };
  
  // Base class for sources. A MediaStreamTrack has an underlying source that
  // provides media. A source can be shared by multiple tracks.
  class MediaSourceInterface : public rtc::RefCountInterface,
                               public NotifierInterface {
   public:
    enum SourceState {
      kInitializing,
      kLive,
      kEnded,
      kMuted
    };
  
    virtual SourceState state() const = 0;
  
    virtual bool remote() const = 0;
  
   protected:
    ~MediaSourceInterface() override = default;
  };
  
  // C++ version of MediaStreamTrack.
  // See: https://www.w3.org/TR/mediacapture-streams/#mediastreamtrack
  class MediaStreamTrackInterface : public rtc::RefCountInterface,
                                    public NotifierInterface {
   public:
    enum TrackState {
      kLive,
      kEnded,
    };
  
    static const char kAudioKind[];
    static const char kVideoKind[];
  
    // The kind() method must return kAudioKind only if the object is a
    // subclass of AudioTrackInterface, and kVideoKind only if the
    // object is a subclass of VideoTrackInterface. It is typically used
    // to protect a static_cast<> to the corresponding subclass.
    virtual std::string kind() const = 0;
  
    // Track identifier.
    virtual std::string id() const = 0;
  
    // A disabled track will produce silence (if audio) or black frames (if
    // video). Can be disabled and re-enabled.
    virtual bool enabled() const = 0;
    virtual bool set_enabled(bool enable) = 0;
  
    // Live or ended. A track will never be live again after becoming ended.
    virtual TrackState state() const = 0;
  
   protected:
    ~MediaStreamTrackInterface() override = default;
  };
  
  // VideoTrackSourceInterface is a reference counted source used for
  // VideoTracks. The same source can be used by multiple VideoTracks.
  // VideoTrackSourceInterface is designed to be invoked on the signaling thread
  // except for rtc::VideoSourceInterface<VideoFrame> methods that will be invoked
  // on the worker thread via a VideoTrack. A custom implementation of a source
  // can inherit AdaptedVideoTrackSource instead of directly implementing this
  // interface.
  class VideoTrackSourceInterface
      : public MediaSourceInterface,
        public rtc::VideoSourceInterface<VideoFrame> {
   public:
    struct Stats {
      // Original size of captured frame, before video adaptation.
      int input_width;
      int input_height;
    };
  
    // Indicates that parameters suitable for screencasts should be automatically
    // applied to RtpSenders.
    // TODO(perkj): Remove these once all known applications have moved to
    // explicitly setting suitable parameters for screencasts and don't need this
    // implicit behavior.
    virtual bool is_screencast() const = 0;
  
    // Indicates that the encoder should denoise video before encoding it.
    // If it is not set, the default configuration is used which is different
    // depending on video codec.
    // TODO(perkj): Remove this once denoising is done by the source, and not by
    // the encoder.
    virtual rtc::Optional<bool> needs_denoising() const = 0;
  
    // Returns false if no stats are available, e.g, for a remote source, or a
    // source which has not seen its first frame yet.
    //
    // Implementation should avoid blocking.
    virtual bool GetStats(Stats* stats) = 0;
  
   protected:
    ~VideoTrackSourceInterface() override = default;
  };
  
  // VideoTrackInterface is designed to be invoked on the signaling thread except
  // for rtc::VideoSourceInterface<VideoFrame> methods that must be invoked
  // on the worker thread.
  // PeerConnectionFactory::CreateVideoTrack can be used for creating a VideoTrack
  // that ensures thread safety and that all methods are called on the right
  // thread.
  class VideoTrackInterface
      : public MediaStreamTrackInterface,
        public rtc::VideoSourceInterface<VideoFrame> {
   public:
    // Video track content hint, used to override the source is_screencast
    // property.
    // See https://crbug.com/653531 and https://github.com/WICG/mst-content-hint.
    enum class ContentHint { kNone, kFluid, kDetailed };
  
    // Register a video sink for this track. Used to connect the track to the
    // underlying video engine.
    void AddOrUpdateSink(rtc::VideoSinkInterface<VideoFrame>* sink,
                         const rtc::VideoSinkWants& wants) override {}
    void RemoveSink(rtc::VideoSinkInterface<VideoFrame>* sink) override {}
  
    virtual VideoTrackSourceInterface* GetSource() const = 0;
  
    virtual ContentHint content_hint() const;
    virtual void set_content_hint(ContentHint hint) {}
  
   protected:
    ~VideoTrackInterface() override = default;
  };
  
  // Interface for receiving audio data from a AudioTrack.
  class AudioTrackSinkInterface {
   public:
    virtual void OnData(const void* audio_data,
                        int bits_per_sample,
                        int sample_rate,
                        size_t number_of_channels,
                        size_t number_of_frames) = 0;
  
   protected:
    virtual ~AudioTrackSinkInterface() {}
  };
  
  // AudioSourceInterface is a reference counted source used for AudioTracks.
  // The same source can be used by multiple AudioTracks.
  class AudioSourceInterface : public MediaSourceInterface {
   public:
    class AudioObserver {
     public:
      virtual void OnSetVolume(double volume) = 0;
  
     protected:
      virtual ~AudioObserver() {}
    };
  
    // TODO(deadbeef): Makes all the interfaces pure virtual after they're
    // implemented in chromium.
  
    // Sets the volume of the source. |volume| is in  the range of [0, 10].
    // TODO(tommi): This method should be on the track and ideally volume should
    // be applied in the track in a way that does not affect clones of the track.
    virtual void SetVolume(double volume) {}
  
    // Registers/unregisters observers to the audio source.
    virtual void RegisterAudioObserver(AudioObserver* observer) {}
    virtual void UnregisterAudioObserver(AudioObserver* observer) {}
  
    // TODO(tommi): Make pure virtual.
    virtual void AddSink(AudioTrackSinkInterface* sink) {}
    virtual void RemoveSink(AudioTrackSinkInterface* sink) {}
  };
  
  // Interface of the audio processor used by the audio track to collect
  // statistics.
  class AudioProcessorInterface : public rtc::RefCountInterface {
   public:
    // Deprecated, use AudioProcessorStatistics instead.
    // TODO(ivoc): Remove this when all implementations have switched to the new
    //             GetStats function. See b/67926135.
    struct AudioProcessorStats {
      AudioProcessorStats()
          : typing_noise_detected(false),
            echo_return_loss(0),
            echo_return_loss_enhancement(0),
            echo_delay_median_ms(0),
            echo_delay_std_ms(0),
            residual_echo_likelihood(0.0f),
            residual_echo_likelihood_recent_max(0.0f),
            aec_divergent_filter_fraction(0.0) {}
      ~AudioProcessorStats() {}
  
      bool typing_noise_detected;
      int echo_return_loss;
      int echo_return_loss_enhancement;
      int echo_delay_median_ms;
      int echo_delay_std_ms;
      float residual_echo_likelihood;
      float residual_echo_likelihood_recent_max;
      float aec_divergent_filter_fraction;
    };
    // This struct maintains the optionality of the stats, and will replace the
    // regular stats struct when all users have been updated.
    struct AudioProcessorStatistics {
      bool typing_noise_detected = false;
      AudioProcessingStats apm_statistics;
    };
  
    // Get audio processor statistics.
    virtual void GetStats(AudioProcessorStats* stats);
  
    // Get audio processor statistics. The |has_remote_tracks| argument should be
    // set if there are active remote tracks (this would usually be true during
    // a call). If there are no remote tracks some of the stats will not be set by
    // the AudioProcessor, because they only make sense if there is at least one
    // remote track.
    // TODO(ivoc): Make pure virtual when all implementions are updated.
    virtual AudioProcessorStatistics GetStats(bool has_remote_tracks);
  
   protected:
    ~AudioProcessorInterface() override = default;
  };
  
  class AudioTrackInterface : public MediaStreamTrackInterface {
   public:
    // TODO(deadbeef): Figure out if the following interface should be const or
    // not.
    virtual AudioSourceInterface* GetSource() const =  0;
  
    // Add/Remove a sink that will receive the audio data from the track.
    virtual void AddSink(AudioTrackSinkInterface* sink) = 0;
    virtual void RemoveSink(AudioTrackSinkInterface* sink) = 0;
  
    // Get the signal level from the audio track.
    // Return true on success, otherwise false.
    // TODO(deadbeef): Change the interface to int GetSignalLevel() and pure
    // virtual after it's implemented in chromium.
    virtual bool GetSignalLevel(int* level);
  
    // Get the audio processor used by the audio track. Return null if the track
    // does not have any processor.
    // TODO(deadbeef): Make the interface pure virtual.
    virtual rtc::scoped_refptr<AudioProcessorInterface> GetAudioProcessor();
  
   protected:
    ~AudioTrackInterface() override = default;
  };
  
  typedef std::vector<rtc::scoped_refptr<AudioTrackInterface> >
      AudioTrackVector;
  typedef std::vector<rtc::scoped_refptr<VideoTrackInterface> >
      VideoTrackVector;
  
  // C++ version of https://www.w3.org/TR/mediacapture-streams/#mediastream.
  //
  // A major difference is that remote audio/video tracks (received by a
  // PeerConnection/RtpReceiver) are not synchronized simply by adding them to
  // the same stream; a session description with the correct "a=msid" attributes
  // must be pushed down.
  //
  // Thus, this interface acts as simply a container for tracks.
  class MediaStreamInterface : public rtc::RefCountInterface,
                               public NotifierInterface {
   public:
    // TODO(steveanton): This could be renamed to id() to match the spec.
    virtual std::string label() const = 0;
  
    virtual AudioTrackVector GetAudioTracks() = 0;
    virtual VideoTrackVector GetVideoTracks() = 0;
    virtual rtc::scoped_refptr<AudioTrackInterface>
        FindAudioTrack(const std::string& track_id) = 0;
    virtual rtc::scoped_refptr<VideoTrackInterface>
        FindVideoTrack(const std::string& track_id) = 0;
  
    virtual bool AddTrack(AudioTrackInterface* track) = 0;
    virtual bool AddTrack(VideoTrackInterface* track) = 0;
    virtual bool RemoveTrack(AudioTrackInterface* track) = 0;
    virtual bool RemoveTrack(VideoTrackInterface* track) = 0;
  
   protected:
    ~MediaStreamInterface() override = default;
  };
  
  }  // namespace webrtc
  
  #endif  // API_MEDIASTREAMINTERFACE_H_
  