refactor video capture in browser process to support device sharing across multiple renderer proc...

content/browser/renderer_host/media/video_capture_manager.h

Index: content/browser/renderer_host/media/video_capture_manager.h
===================================================================
--- content/browser/renderer_host/media/video_capture_manager.h	(revision 108126)
+++ content/browser/renderer_host/media/video_capture_manager.h	(working copy)
@@ -2,14 +2,16 @@
 // 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 as well as enumerate
-// available video capture devices. All functions are expected to be called from
-// the Browser::IO thread. VideoCaptureManager will open OS dependent instances
-// of VideoCaptureDevice. A device can only be opened once.
+// 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.
+// 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 "base/threading/thread.h"
@@ -19,6 +21,9 @@
 #include "media/video/capture/video_capture_device.h"
 #include "media/video/capture/video_capture_types.h"
 
+class VideoCaptureController;
+class VideoCaptureControllerEventHandler;
+
 namespace media_stream {
 
 // VideoCaptureManager opens/closes and start/stops video capture devices.
@@ -66,7 +71,21 @@
   void UseFakeDevice();
   MessageLoop* GetMessageLoop();
 
+  // Called by VideoCaptureHost to get a controller for |capture_params|.
+  // The controller is returned via calling |added_cb|.
+  void AddController(
+      const media::VideoCaptureParams& capture_params,

[perkj_chrome, 2011/11/02 09:18:13]

Why is capture_params needed both here and in void Start? Should only need them
once.

Even better: Remove AddController and RemoveController. They can be combined
with Start and Stop above.
VideoCaptureHost call Start(capture_params, handler)
VideoCapureManager::Start looks up the handler and creates a new controller if
needed. The controller implements media::VideoCaptureDevice::EventHander so
there is no longer any need for the VideoCaptureHost to pass it in since
VideoCaptureManager now owns / creates it.

This way you should be able to simplify things a bit.

[wjia(left Chromium), 2011/11/03 07:02:02]

AddController needs session_id in capture_params (I may just use session_id
directly), while Start() needs it for capture configurations.

I have thought about moving most of the logic into Manager. It indeed simplifies
code a bit. But it makes more sense for Host to deal with Controller directly
when it returns buffers (calling controller->ReturnBuffer()). Manager is mainly
for open/close/start/stop of device, while Controller is for other operations.

+      VideoCaptureControllerEventHandler* handler,
+      base::Callback<void(VideoCaptureController*)> added_cb);
+  // Called by VideoCaptureHost to remove the |controller|.
+  void RemoveController(
+      VideoCaptureController* controller,
+      VideoCaptureControllerEventHandler* handler);
+
  private:
+  typedef std::list<VideoCaptureControllerEventHandler*> Handlers;
+  struct Controller;
+
   // Called by the public functions, executed on vc_device_thread_.
   void OnEnumerateDevices();
   void OnOpen(int capture_session_id, const StreamDeviceInfo& device);
@@ -75,6 +94,13 @@
                media::VideoCaptureDevice::EventHandler* video_capture_receiver);
   void OnStop(const media::VideoCaptureSessionId capture_session_id,
               base::Closure stopped_cb);
+  void DoAddControllerOnDeviceThread(
+      const media::VideoCaptureParams capture_params,
+      VideoCaptureControllerEventHandler* handler,
+      base::Callback<void(VideoCaptureController*)> added_cb);
+  void DoRemoveControllerOnDeviceThread(
+      VideoCaptureController* controller,
+      VideoCaptureControllerEventHandler* handler);
 
   // Executed on Browser::IO thread to call Listener.
   void OnOpened(int capture_session_id);
@@ -94,6 +120,7 @@
   bool DeviceOpened(const media::VideoCaptureDevice::Name& device_name);
   bool DeviceOpened(const StreamDeviceInfo& device_info);
   bool IsOnCaptureDeviceThread() const;
+  media::VideoCaptureDevice* GetDeviceInternal(int capture_session_id);
 
   // Thread for all calls to VideoCaptureDevice.
   base::Thread vc_device_thread_;
@@ -111,6 +138,13 @@
   // Set to true if using fake devices for testing, false by default.
   bool use_fake_device_;
 
+  // Only accessed from vc_device_thread_.
+  // VideoCaptureManager owns all VideoCaptureController's and is responsible
+  // for deleting the instances when they are not used any longer.
+  // VideoCaptureDevice is one-to-one mapped to VideoCaptureController.
+  typedef std::map<media::VideoCaptureDevice*, Controller*> Controllers;
+  Controllers controllers_;
+
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureManager);
 };