Queue commands to the Os to start a video device.

content/browser/renderer_host/media/video_capture_manager.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.
 
 // VideoCaptureManager is used to open/close, start/stop, enumerate available
 // video capture devices, and manage VideoCaptureController's.
 // All functions are expected to be called from Browser::IO thread. Some helper
 // functions (*OnDeviceThread) will dispatch operations to the device thread.
 // VideoCaptureManager will open OS dependent instances of VideoCaptureDevice.
 // A device can only be opened once.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_
 
+#include <list>
 #include <map>
 #include <set>
 #include <string>
 
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_vector.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/process/process_handle.h"
 #include "base/timer/elapsed_timer.h"
 #include "content/browser/renderer_host/media/media_stream_provider.h"
 #include "content/browser/renderer_host/media/video_capture_controller_event_handler.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
 #include "media/video/capture/video_capture_device.h"
 #include "media/video/capture/video_capture_device_factory.h"
@@ skipping 145 matching lines @@
   // Consolidates the cached devices list with the list of currently connected
   // devices in the system |names_snapshot|. Retrieves the supported formats of
   // the new devices and sends the new cache to OnDevicesInfoEnumerated().
   void ConsolidateDevicesInfoOnDeviceThread(
       base::Callback<void(const media::VideoCaptureDeviceInfos&)>
           on_devices_enumerated_callback,
       MediaStreamType stream_type,
       const media::VideoCaptureDeviceInfos& old_device_info_cache,
       scoped_ptr<media::VideoCaptureDevice::Names> names_snapshot);
 
-  // Creates and Starts a new VideoCaptureDevice, storing the result in
-  // |entry->video_capture_device|. Ownership of |client| passes to
+  // Starting a capture device can take 1-2 seconds.
+  // To avoid multiple unnecessary start/stop commands to the OS, each start
+  // request is queued in |device_start_queue_|.
+  // QueueStartDevice creates a new entry in |device_start_queue_| and posts a
+  // request to start the device on the device thread unless there is
+  // another request pending start.
+  void QueueStartDevice(media::VideoCaptureSessionId session_id,
+                        DeviceEntry* entry,
+                        const media::VideoCaptureParams& params);
+  void OnDeviceStarted(DeviceEntry* device_entry,
+                       scoped_ptr<media::VideoCaptureDevice> device);
+  void DoStopDevice(DeviceEntry* entry);
+  void HandleQueuedStartRequest();
+
+  // Creates and Starts a new VideoCaptureDevice. The resulting
+  // VideoCaptureDevice is returned to the IO-thread and stored in
+  // a DeviceEntry in |devices_|. Ownership of |client| passes to
   // the device.
-  void DoStartDeviceOnDeviceThread(
+  scoped_ptr<media::VideoCaptureDevice> DoStartDeviceOnDeviceThread(
       media::VideoCaptureSessionId session_id,
-      DeviceEntry* entry,
+      const std::string& device_id,
+      MediaStreamType stream_type,
       const media::VideoCaptureParams& params,
       scoped_ptr<media::VideoCaptureDevice::Client> client);
 
   // Stops and destroys the VideoCaptureDevice held in
-  // |entry->video_capture_device|.
-  void DoStopDeviceOnDeviceThread(DeviceEntry* entry);
+  // |device|.
+  void DoStopDeviceOnDeviceThread(scoped_ptr<media::VideoCaptureDevice> device);
 
   media::VideoCaptureDeviceInfo* FindDeviceInfoById(
       const std::string& id,
       media::VideoCaptureDeviceInfos& device_vector);
 
   void SetDesktopCaptureWindowIdOnDeviceThread(DeviceEntry* entry,
                                                gfx::NativeViewId window_id);
 
   void SaveDesktopCaptureWindowIdOnDeviceThread(
       media::VideoCaptureSessionId session_id,
@@ skipping 12 matching lines @@
   // determine which device to use when StartCaptureForClient() occurs. Used
   // only on the IO thread.
   SessionMap sessions_;
 
   // An entry, kept in a map, that owns a VideoCaptureDevice and its associated
   // VideoCaptureController. VideoCaptureManager owns all VideoCaptureDevices
   // and VideoCaptureControllers and is responsible for deleting the instances
   // when they are not used any longer.
   //
   // The set of currently started VideoCaptureDevice and VideoCaptureController
-  // objects is only accessed from IO thread, though the DeviceEntry instances
-  // themselves may visit to the device thread for device creation and
-  // destruction.
+  // objects is only accessed from IO thread.
   struct DeviceEntry {
     DeviceEntry(MediaStreamType stream_type,
                 const std::string& id,
                 scoped_ptr<VideoCaptureController> controller);
     ~DeviceEntry();
 
     const MediaStreamType stream_type;
     const std::string id;
 
     // The controller. Only used from the IO thread.
     scoped_ptr<VideoCaptureController> video_capture_controller;
 
     // The capture device. Only used from the device thread.
     scoped_ptr<media::VideoCaptureDevice> video_capture_device;
   };
-  typedef std::set<DeviceEntry*> DeviceEntries;
+
+  typedef ScopedVector<DeviceEntry> DeviceEntries;
+  // Currently opened devices. The device may or may not be started.
   DeviceEntries devices_;
 
+  // Struct used for queuing request for starting a device.
+  struct CaptureDeviceStartRequest {
+    CaptureDeviceStartRequest(
+        DeviceEntry* entry,
+        media::VideoCaptureSessionId session_id,
+        const media::VideoCaptureParams& params);
+
+    DeviceEntry* entry; // Owned by |devices_|
+    media::VideoCaptureSessionId session_id;
+    media::VideoCaptureParams params;
+    // Set to true if the device should be stopped before it have successfully

[tommi (sloooow) - chröme, 2014/12/17 14:46:12]

it have -> it has

[perkj_chrome, 2014/12/18 12:15:32]

Done.

+    // been started.
+    bool abort_start;
+  };
+
+  typedef std::list<CaptureDeviceStartRequest> DeviceStartQueue;
+  DeviceStartQueue device_start_queue_;
+
   // Device creation factory injected on construction from MediaStreamManager or
   // from the test harness.
   scoped_ptr<media::VideoCaptureDeviceFactory> video_capture_device_factory_;
 
   // Local cache of the enumerated video capture devices' names and capture
   // supported formats. A snapshot of the current devices and their capabilities
   // is composed in VideoCaptureDeviceFactory::EnumerateDeviceNames() and
   // ConsolidateDevicesInfoOnDeviceThread(), and this snapshot is used to update
   // this list in OnDevicesInfoEnumerated(). GetDeviceSupportedFormats() will
   // use this list if the device is not started, otherwise it will retrieve the
   // active device capture format from the VideoCaptureController associated.
   media::VideoCaptureDeviceInfos devices_info_cache_;
 
   // Accessed on the device thread only.
   std::map<media::VideoCaptureSessionId, gfx::NativeViewId>
       notification_window_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_MANAGER_H_