Let default device in PulseAudio be the system default device

media/audio/pulse/pulse_output.h

 // Copyright (c) 2012 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.
 //
 // Creates an audio output stream based on the PulseAudio asynchronous API;
 // specifically using the pa_threaded_mainloop model.
 //
 // If the stream is successfully opened, Close() must be called before the
 // stream is deleted as Close() is responsible for ensuring resource cleanup
 // occurs.
 //
 // This object is designed so that all AudioOutputStream methods will be called
 // on the same thread that created the object.
 //
 // WARNING: This object blocks on internal PulseAudio calls in Open() while
 // waiting for PulseAudio's context structure to be ready.  It also blocks in
 // inside PulseAudio in Start() and repeated during playback, waiting for
 // PulseAudio write callbacks to occur.
 
 #ifndef MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_
 #define MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_
 
+#include <pulse/pulseaudio.h>
 #include <stddef.h>
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_parameters.h"
 
@@ skipping 23 matching lines @@
 
  private:
   // Called by PulseAudio when |pa_stream_| change state.  If an unexpected
   // failure state change happens and |source_callback_| is set
   // this method will forward the error via OnError().
   static void StreamNotifyCallback(pa_stream* s, void* p_this);
 
   // Called by PulseAudio when it needs more audio data.
   static void StreamRequestCallback(pa_stream* s, size_t len, void* p_this);
 
+  // pa_context_get_server_info callback. It's used by
+  // GetSystemDefaultOutputDevice to set |default_system_device_name_| to the
+  // default system output device.
+  static void GetSystemDefaultOutputDeviceCallback(pa_context* context,
+                                                   const pa_server_info* info,
+                                                   void* user_data);
+
+  // Initialize |pa_mainloop_| and |pa_context_| and prepare them for creating
+  // an output stream.
+  bool InitializeMainloopAndContext();
+
+  // Get default system output device for the output stream.
+  void GetSystemDefaultOutputDevice();
+
   // Fulfill a write request from the write request callback.  Outputs silence
   // if the request could not be fulfilled.
   void FulfillWriteRequest(size_t requested_bytes);
 
   // Close() helper function to free internal structs.
   void Reset();
 
   // AudioParameters from the constructor.
   const AudioParameters params_;
 
   // The device ID for the device to open.
   const std::string device_id_;
+  // The name of the system default device. Set by
+  // GetSystemDefaultOutputDeviceCallback if |device_id_| is set to be the
+  // default device.
+  std::string default_system_device_name_;
 
   // Audio manager that created us.  Used to report that we've closed.
   AudioManagerBase* manager_;
 
   // PulseAudio API structs.
   pa_context* pa_context_;
   pa_threaded_mainloop* pa_mainloop_;
   pa_stream* pa_stream_;
 
   // Float representation of volume from 0.0 to 1.0.
   float volume_;
 
   // Callback to audio data source.  Must only be modified while holding a lock
   // on |pa_mainloop_| via pa_threaded_mainloop_lock().
   AudioSourceCallback* source_callback_;
 
   // Container for retrieving data from AudioSourceCallback::OnMoreData().
   scoped_ptr<AudioBus> audio_bus_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(PulseAudioOutputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_