Switching audio clients to using RestartableAudioRendererSink interface as a sink.

media/audio/restartable_audio_output_device_impl.h

+// Copyright (c) 2016 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_RESTARTABLE_AUDIO_OUTPUT_DEVICE_IMPL_H_
+#define MEDIA_AUDIO_RESTARTABLE_AUDIO_OUTPUT_DEVICE_IMPL_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+#include "media/audio/audio_parameters.h"
+#include "media/base/audio_renderer_sink.h"
+#include "media/base/media_export.h"
+#include "media/base/output_device.h"
+
+// Adapter class to implement RestartableAudioOutputDevice interface on top of
+// AudioOutputDevice. Used by RestartableAudioOutputDeviceFactory to instanciate
+// the interface in cases when audio output should not go through
+// AudioRendererMixer (as opposite to AudioRendererMixerInput implementation of
+// the interface).
+//
+// Behavior differences from AudioOutputDevice:
+// (1) Restartable, i.e. Start() can be called again after Stop().
+//     - This is not utilized now, but implemented in order to be aligned with
+//       AudioRendererMixerInput, which is a restartable sink.
+// (2) Does not play on start (similar to AudioRendererMixerInput)
+// (3) Play/Pause do not take an effect if Start() has not been called.
+//     - Similar to AudioRendererMixerInput.
+//
+// Behaviour differences from AudioRendererMixerInput:
+// (1) SwitchOutputDevice() is not implemented.
+//     - Used for media elements playout only, and there is not plan to use
+//       RestartableAudioOutputDeviceImpl as a sink for their playout.
+namespace media {
+class AudioOutputDevice;
+
+class MEDIA_EXPORT RestartableAudioOutputDeviceImpl
+    : public RestartableAudioRendererSink,
+      public OutputDevice {
+ public:
+  // TODO(olka): If device switching needs to be supported, these callbacks
+  // should receive session_id, device_id and security_origin as parameters.
+  typedef base::Callback<scoped_refptr<AudioOutputDevice>()> GetSinkCB;
+  typedef base::Callback<AudioParameters()> GetHWParamsCB;
+
+  RestartableAudioOutputDeviceImpl(const GetSinkCB& get_sink_cb,
+                                   const GetHWParamsCB& get_hw_params_cb);
+
+  //----AudioRendererSink implementation.
+  // NOTE: Clients must call Initialize() before starting it for the first time.
+  // Calling Initialize() between Stop() and subsequent Start() is optional,
+  void Initialize(const AudioParameters& params,
+                  RenderCallback* callback) override;
+  void Start() override;
+  void Stop() override;
+
+  // Play/Pause take an effect only when the device is already started. This is
+  // to copy AudioRendererMixerInput behavior.
+  void Play() override;
+  void Pause() override;
+
+  bool SetVolume(double volume) override;
+  OutputDevice* GetOutputDevice() override;
+
+  //----OutputDevice implementation.
+  AudioParameters GetOutputParameters() override;
+  OutputDeviceStatus GetDeviceStatus() override;
+
+ protected:
+  // Magic required by ref_counted.h to avoid any code deleting the object
+  // accidentally while there are references to it.
+  friend class base::RefCountedThreadSafe<RestartableAudioOutputDeviceImpl>;
+  ~RestartableAudioOutputDeviceImpl() override;
+
+ private:
+  // kStopped -> kStarted -> kPlaying <-> kPaused
+  //     ^           |           |           |
+  //     '-----------+-----------+-----------'
+  enum State { kStopped = 0, kStarted, kPlaying, kPaused };
+
+  // Unsupported OutputDevice implementation
+  void SwitchOutputDevice(const std::string& device_id,
+                          const url::Origin& security_origin,
+                          const SwitchOutputDeviceCB& callback) override;
+
+  // Internal state.
+  State state_;
+
+  // Output volume.
+  double volume_;
+
+  // Output audio parameters.
+  AudioParameters params_;
+
+  // Source of audio data which is provided to the sink.
+  AudioRendererSink::RenderCallback* render_cb_;
+
+  // Factory callback to create a new sink, provided during construction.
+  const GetSinkCB get_sink_cb_;
+
+  // Callback to access hardware output parameters, provided during
+  // construction.
+  const GetHWParamsCB get_hw_params_cb_;
+
+  scoped_refptr<AudioOutputDevice> sink_;
+
+  DISALLOW_COPY_AND_ASSIGN(RestartableAudioOutputDeviceImpl);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_RESTARTABLE_AUDIO_OUTPUT_DEVICE_IMPL_H_