Support audio output device enumeration and selection in PPAPI

content/renderer/pepper/pepper_platform_audio_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.
 
 #ifndef CONTENT_RENDERER_PEPPER_PEPPER_PLATFORM_AUDIO_OUTPUT_H_
 #define CONTENT_RENDERER_PEPPER_PEPPER_PLATFORM_AUDIO_OUTPUT_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "media/audio/audio_output_ipc.h"
+#include "media/base/audio_parameters.h"
+#include "media/base/output_device_info.h"
 
-namespace media {
-class AudioParameters;
+namespace base {
+class OneShotTimer;
+class SingleThreadTaskRunner;
 }
 
-namespace base {
-class SingleThreadTaskRunner;
+namespace {
+#if defined(OS_WIN) || defined(OS_MACOSX)
+  const int64_t kMaxAuthorizationTimeoutMs = 4000;
+#else
+  const int64_t kMaxAuthorizationTimeoutMs = 0;  // No timeout.
+#endif
 }
 
 namespace content {
 class AudioHelper;
+class PepperAudioOutputHost;
+
+// We need to support both public PPAPI |PPB_Audio| and the new
+// dev PPAPI |PPB_AudioOutput_Dev| at the same time, so that the
+// existing users of |PPB_Audio| won't be affected.
+// To achieve this, we have to keep references to both |AudioHelper|
+// object and |PepperAudioOutputHost| object, so we can dispatch
+// callbacks properly.

[bbudge, 2017/03/23 18:05:45]

Your changes to this class risk breaking the old PPB_Audio interface.

I think it would be better to create a separate class for the new behavior, e.g.
PepperPlatformAudioOutputDev.

[Xing, 2017/03/29 21:14:32]

New implementation has been moved to pepper_platform_audio_output_dev.cc{h}, new
class is called PepperPlatformAudioOutputDev.

 
 class PepperPlatformAudioOutput
     : public media::AudioOutputIPCDelegate,
       public base::RefCountedThreadSafe<PepperPlatformAudioOutput> {
  public:
   // Factory function, returns NULL on failure. StreamCreated() will be called
   // when the stream is created.
   static PepperPlatformAudioOutput* Create(int sample_rate,
                                            int frames_per_buffer,
                                            int source_render_frame_id,
                                            AudioHelper* client);
 
+  static PepperPlatformAudioOutput* Create(int render_frame_id,
+                                           const std::string& device_id,
+                                           const GURL& document_url,
+                                           int sample_rate,
+                                           int frames_per_buffer,
+                                           PepperAudioOutputHost* client);
+
   // The following three methods are all called on main thread.
 
+  // Request authorization to use the device.

[bbudge, 2017/03/23 18:05:45]

nit: comment isn't necessary

[Xing, 2017/03/29 21:14:32]

Done.

+  void RequestDeviceAuthorization();
+
   // Starts the playback. Returns false on error or if called before the
   // stream is created or after the stream is closed.
   bool StartPlayback();
 
   // Stops the playback. Returns false on error or if called before the stream
   // is created or after the stream is closed.
   bool StopPlayback();
 
   // Sets the volume. Returns false on error or if called before the stream
   // is created or after the stream is closed.
@@ skipping 10 matching lines @@
                           const std::string& matched_device_id) override;
   void OnStreamCreated(base::SharedMemoryHandle handle,
                        base::SyncSocket::Handle socket_handle,
                        int length) override;
   void OnIPCClosed() override;
 
  protected:
   ~PepperPlatformAudioOutput() override;
 
  private:
+  enum State {
+    IPC_CLOSED,       // No more IPCs can take place.
+    IDLE,             // Not started.
+    AUTHORIZING,      // Sent device authorization request, waiting for reply.
+    AUTHORIZED,       // Successful device authorization received.
+    CREATING_STREAM,  // Waiting for OnStreamCreated() to be called back.
+    PAUSED,   // Paused.  OnStreamCreated() has been called.  Can Play()/Stop().
+    PLAYING,  // Playing back.  Can Pause()/Stop().
+  };
+
   friend class base::RefCountedThreadSafe<PepperPlatformAudioOutput>;
 
   PepperPlatformAudioOutput();
+  PepperPlatformAudioOutput(int render_frame_id,
+                            const std::string& device_id,
+                            const GURL& document_url,
+                            base::TimeDelta authorization_timeout);
 
+  // Used for old Pepper audio interface.

[bbudge, 2017/03/23 18:05:45]

nit: be specific, PPB_Audio

[Xing, 2017/03/29 21:14:32]

Done.

   bool Initialize(int sample_rate,
                   int frames_per_buffer,
                   int source_render_frame_id,
                   AudioHelper* client);
 
+  // Creates audio stream. Used for new Pepper audio output interface.

[bbudge, 2017/03/23 18:05:45]

ditto: PPB_AudioOutput_Dev

[Xing, 2017/03/29 21:14:32]

Done.

+  bool Initialize(int sample_rate,
+                  int frames_per_buffer,
+                  PepperAudioOutputHost* client);
+
   // I/O thread backends to above functions.
+  // Used only by old Pepper audio interface.

[bbudge, 2017/03/23 18:05:45]

ditto

[Xing, 2017/03/29 21:14:32]

Done.

   void InitializeOnIOThread(const media::AudioParameters& params);
+
+  void RequestDeviceAuthorizationOnIOThread();

[bbudge, 2017/03/23 18:05:44]

I assume these are only used to support PPB_AudioOutput_Dev. Could you segregate
the methods into two groups, for the two Pepper interfaces?

[Xing, 2017/03/29 21:14:32]

Done.

+  void CreateStreamOnIOThread(const media::AudioParameters& params);
   void StartPlaybackOnIOThread();
   void StopPlaybackOnIOThread();
   void SetVolumeOnIOThread(double volume);
   void ShutDownOnIOThread();
 
+  void NotifyStreamCreationFailed();
+
   // The client to notify when the stream is created. THIS MUST ONLY BE
   // ACCESSED ON THE MAIN THREAD.
   AudioHelper* client_;
+  // TODO: This PepperAudioOutputHost client will eventually replace

[bbudge, 2017/03/23 18:05:45]

nit: chromium style requires TODO(owner), e.g. TODO(xing)

Do you really intend to do this work?

[Xing, 2017/03/29 21:14:32]

Removed this TODO comment, since future modification to Pepper will not be
accepted.

+  // AudioHelper client. Only one of them can be valid. We keep them
+  // for backward compatibility purpose.
+  PepperAudioOutputHost* host_client_;
 
   // Used to send/receive IPC. THIS MUST ONLY BE ACCESSED ON THE
   // I/O thread except to send messages and get the message loop.
   std::unique_ptr<media::AudioOutputIPC> ipc_;
 
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 
+  // The frame containing the Pepper widget.
+  int render_frame_id_;
+
+  // Initialized on the main thread and accessed on the I/O thread afterwards.
+  media::AudioParameters params_;
+
+  // Current state (must only be accessed from the IO thread).
+  State state_;
+
+  // State of Start() calls before OnDeviceAuthorized() is called.
+  bool start_on_authorized_;
+
+  // State of StartPlayback() calls before OnStreamCreated() is called.
+  bool play_on_start_;
+
+  // The media session ID used to identify which output device to be started.
+  // Only used by Unified IO.

[bbudge, 2017/03/23 18:05:44]

What is Unified IO?

[Xing, 2017/03/29 21:14:32]

Removed.

+  int session_id_;
+
+  // ID of hardware output device to be used (provided session_id_ is zero)
+  const std::string device_id_;
+  const url::Origin security_origin_;
+
+  // If |device_id_| is empty and |session_id_| is not, |matched_device_id_| is
+  // received in OnDeviceAuthorized().
+  std::string matched_device_id_;
+
+  base::WaitableEvent did_receive_auth_;
+  media::AudioParameters output_params_;
+  media::OutputDeviceStatus device_status_;
+
+  const base::TimeDelta auth_timeout_;
+  std::unique_ptr<base::OneShotTimer> auth_timeout_action_;
+
   DISALLOW_COPY_AND_ASSIGN(PepperPlatformAudioOutput);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PEPPER_PEPPER_PLATFORM_AUDIO_OUTPUT_H_