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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 //
      5 // VideoCaptureController is the glue between a VideoCaptureDevice and all
      6 // VideoCaptureHosts that have connected to it. A controller exists on behalf of
      7 // one (and only one) VideoCaptureDevice; both are owned by the
      8 // VideoCaptureManager.
      9 //
     10 // The VideoCaptureController is responsible for:
     11 //
     12 //   * Allocating and keeping track of shared memory buffers, and filling them
     13 //     with I420 video frames for IPC communication between VideoCaptureHost (in
     14 //     the browser process) and VideoCaptureMessageFilter (in the renderer
     15 //     process).
     16 //   * Broadcasting the events from a single VideoCaptureDevice, fanning them
     17 //     out to multiple clients.
     18 //   * Keeping track of the clients on behalf of the VideoCaptureManager, making
     19 //     it possible for the Manager to delete the Controller and its Device when
     20 //     there are no clients left.
     21 //
     22 // A helper class, VCC::VideoCaptureDeviceClient, is responsible for:
     23 //
     24 //   * Conveying events from the device thread (where VideoCaptureDevices live)
     25 //     the IO thread (where the VideoCaptureController lives).
     26 //   * Performing some image transformations on the output of the Device;
     27 //     specifically, colorspace conversion and rotation.
     28 //
     29 // Interactions between VideoCaptureController and other classes:
     30 //
     31 //   * VideoCaptureController indirectly observes a VideoCaptureDevice
     32 //     by means of its proxy, VideoCaptureDeviceClient, which implements
     33 //     the VideoCaptureDevice::Client interface. The proxy forwards
     34 //     observed events to the VideoCaptureController on the IO thread.
     35 //   * A VideoCaptureController interacts with its clients (VideoCaptureHosts)
     36 //     via the VideoCaptureControllerEventHandler interface.
     37 //   * Conversely, a VideoCaptureControllerEventHandler (typically,
     38 //     VideoCaptureHost) will interact directly with VideoCaptureController to
     39 //     return leased buffers by means of the ReturnBuffer() public method of
     40 //     VCC.
     41 //   * VideoCaptureManager (which owns the VCC) interacts directly with
     42 //     VideoCaptureController through its public methods, to add and remove
     43 //     clients.
     44 //
     45 // VideoCaptureController is not thread safe and operates on the IO thread only.
     46 
     47 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_CONTROLLER_H_
     48 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_CONTROLLER_H_
     49 
     50 #include <list>
     51 
     52 #include "base/compiler_specific.h"
     53 #include "base/memory/ref_counted.h"
     54 #include "base/memory/scoped_ptr.h"
     55 #include "base/memory/weak_ptr.h"
     56 #include "base/process/process.h"
     57 #include "content/browser/renderer_host/media/video_capture_buffer_pool.h"
     58 #include "content/browser/renderer_host/media/video_capture_controller_event_handler.h"
     59 #include "content/common/content_export.h"
     60 #include "content/common/media/video_capture.h"
     61 #include "media/video/capture/video_capture.h"
     62 #include "media/video/capture/video_capture_device.h"
     63 #include "media/video/capture/video_capture_types.h"
     64 
     65 namespace content {
     66 class VideoCaptureBufferPool;
     67 
     68 class CONTENT_EXPORT VideoCaptureController {
     69  public:
     70   VideoCaptureController();
     71   virtual ~VideoCaptureController();
     72 
     73   base::WeakPtr<VideoCaptureController> GetWeakPtr();
     74 
     75   // Return a new VideoCaptureDeviceClient to forward capture events to this
     76   // instance.
     77   scoped_ptr<media::VideoCaptureDevice::Client> NewDeviceClient();
     78 
     79   // Start video capturing and try to use the resolution specified in |params|.
     80   // Buffers will be shared to the client as necessary. The client will continue
     81   // to receive frames from the device until RemoveClient() is called.
     82   void AddClient(const VideoCaptureControllerID& id,
     83                  VideoCaptureControllerEventHandler* event_handler,
     84                  base::ProcessHandle render_process,
     85                  media::VideoCaptureSessionId session_id,
     86                  const media::VideoCaptureParams& params);
     87 
     88   // Stop video capture. This will take back all buffers held by by
     89   // |event_handler|, and |event_handler| shouldn't use those buffers any more.
     90   // Returns the session_id of the stopped client, or
     91   // kInvalidMediaCaptureSessionId if the indicated client was not registered.
     92   int RemoveClient(const VideoCaptureControllerID& id,
     93                    VideoCaptureControllerEventHandler* event_handler);
     94 
     95   int GetClientCount();
     96 
     97   // API called directly by VideoCaptureManager in case the device is
     98   // prematurely closed.
     99   void StopSession(int session_id);
    100 
    101   // Return a buffer previously given in
    102   // VideoCaptureControllerEventHandler::OnBufferReady.
    103   void ReturnBuffer(const VideoCaptureControllerID& id,
    104                     VideoCaptureControllerEventHandler* event_handler,
    105                     int buffer_id);
    106 
    107   const media::VideoCaptureFormat& GetVideoCaptureFormat() const;
    108 
    109  private:
    110   class VideoCaptureDeviceClient;
    111 
    112   struct ControllerClient;
    113   typedef std::list<ControllerClient*> ControllerClients;
    114 
    115   // Worker functions on IO thread. Called by the VideoCaptureDeviceClient.
    116   void DoIncomingCapturedI420BufferOnIOThread(
    117       scoped_refptr<media::VideoCaptureDevice::Client::Buffer> buffer,
    118       const gfx::Size& dimensions,
    119       int frame_rate,
    120       base::Time timestamp);
    121   void DoErrorOnIOThread();
    122   void DoDeviceStoppedOnIOThread();
    123   void DoBufferDestroyedOnIOThread(int buffer_id_to_drop);
    124 
    125   // Find a client of |id| and |handler| in |clients|.
    126   ControllerClient* FindClient(
    127       const VideoCaptureControllerID& id,
    128       VideoCaptureControllerEventHandler* handler,
    129       const ControllerClients& clients);
    130 
    131   // Find a client of |session_id| in |clients|.
    132   ControllerClient* FindClient(
    133       int session_id,
    134       const ControllerClients& clients);
    135 
    136   // The pool of shared-memory buffers used for capturing.
    137   const scoped_refptr<VideoCaptureBufferPool> buffer_pool_;
    138 
    139   // All clients served by this controller.
    140   ControllerClients controller_clients_;
    141 
    142   // Takes on only the states 'STARTED' and 'ERROR'. 'ERROR' is an absorbing
    143   // state which stops the flow of data to clients.
    144   VideoCaptureState state_;
    145 
    146   media::VideoCaptureFormat video_capture_format_;
    147 
    148   base::WeakPtrFactory<VideoCaptureController> weak_ptr_factory_;
    149 
    150   DISALLOW_COPY_AND_ASSIGN(VideoCaptureController);
    151 };
    152 
    153 }  // namespace content
    154 
    155 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_CONTROLLER_H_
    156