root/media/audio/audio_logging.h

INCLUDED FROM

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_AUDIO_AUDIO_LOGGING_H_
#define MEDIA_AUDIO_AUDIO_LOGGING_H_

#include <string>

#include "base/memory/scoped_ptr.h"

namespace media {
class AudioParameters;

// AudioLog logs state information about an active audio component.  Each method
// takes a |component_id| along with method specific information.  Its methods
// are safe to call from any thread.
class AudioLog {
 public:
  virtual ~AudioLog() {}

  // Called when an audio component is created.  |params| are the parameters of
  // the created stream.  |device_id| is the id of the audio device opened by
  // the created stream.
  virtual void OnCreated(int component_id,
                         const media::AudioParameters& params,
                         const std::string& device_id) = 0;

  // Called when an audio component is started, generally this is synonymous
  // with "playing."
  virtual void OnStarted(int component_id) = 0;

  // Called when an audio component is stopped, generally this is synonymous
  // with "paused."
  virtual void OnStopped(int component_id) = 0;

  // Called when an audio component is closed, generally this is synonymous
  // with "deleted."
  virtual void OnClosed(int component_id) = 0;

  // Called when an audio component encounters an error.
  virtual void OnError(int component_id) = 0;

  // Called when an audio component changes volume.  |volume| is the new volume.
  virtual void OnSetVolume(int component_id, double volume) = 0;
};

// AudioLogFactory dispenses AudioLog instances to owning classes for tracking
// AudioComponent behavior.  All AudioComponents have the concept of an owning
// class:
//
//    - AudioInputRendererHost for AudioInputController
//    - AudioRendererHost for AudioOutputController
//    - AudioOutputDispatcherImpl for AudioOutputStream
//
// Each of these owning classes may own multiple instances of each component, as
// such each AudioLog supports logging for multiple instances.
class AudioLogFactory {
 public:
  enum AudioComponent {
    // Input controllers have a 1:1 mapping with streams, so there's no need to
    // track both controllers and streams.
    AUDIO_INPUT_CONTROLLER,
    // Output controllers may or may not be backed by an active stream, so we
    // need to track both controllers and streams.
    AUDIO_OUTPUT_CONTROLLER,
    AUDIO_OUTPUT_STREAM,
    AUDIO_COMPONENT_MAX
  };

  // Create a new AudioLog object for tracking the behavior for one or more
  // instances of the given component.  Each instance of an "owning" class must
  // create its own AudioLog.
  virtual scoped_ptr<AudioLog> CreateAudioLog(AudioComponent component) = 0;

 protected:
  virtual ~AudioLogFactory() {}
};

}  // namespace media

#endif  // MEDIA_AUDIO_AUDIO_LOGGING_H_