media/capture/content/screen_capture_device_core.h

   1 // Copyright 2014 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 #ifndef MEDIA_CAPTURE_SCREEN_CAPTURE_DEVICE_CORE_H_
   6 #define MEDIA_CAPTURE_SCREEN_CAPTURE_DEVICE_CORE_H_
   7
   8 #include <string>
   9
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/memory/weak_ptr.h"
  12 #include "base/threading/thread_checker.h"
  13 #include "media/base/media_export.h"
  14 #include "media/capture/content/thread_safe_capture_oracle.h"
  15 #include "media/capture/video/video_capture_device.h"
  16
  17 namespace media {
  18
  19 struct VideoCaptureParams;
  20
  21 class ThreadSafeCaptureOracle;
  22
  23 // Keeps track of the video capture source frames and executes copying.
  24 class MEDIA_EXPORT VideoCaptureMachine {
  25  public:
  26   VideoCaptureMachine();
  27   virtual ~VideoCaptureMachine();
  28
  29   // Starts capturing.
  30   // |callback| is invoked with true if succeeded. Otherwise, with false.
  31   virtual void Start(const scoped_refptr<ThreadSafeCaptureOracle>& oracle_proxy,
  32                      const VideoCaptureParams& params,
  33                      const base::Callback<void(bool)> callback) = 0;
  34
  35   // Stops capturing.
  36   // |callback| is invoked after the capturing has stopped.
  37   virtual void Stop(const base::Closure& callback) = 0;
  38
  39   // Returns true if the video capture is configured to monitor end-to-end
  40   // system utilization, and alter frame sizes and/or frame rates to mitigate
  41   // overloading or under-utilization.
  42   virtual bool IsAutoThrottlingEnabled() const;
  43
  44  private:
  45   DISALLOW_COPY_AND_ASSIGN(VideoCaptureMachine);
  46 };
  47
  48 // The "meat" of a content video capturer.
  49 //
  50 // Separating this from the "shell classes" WebContentsVideoCaptureDevice and
  51 // DesktopCaptureDeviceAura allows safe destruction without needing to block any
  52 // threads, as well as code sharing.
  53 //
  54 // ScreenCaptureDeviceCore manages a simple state machine and the pipeline
  55 // (see notes at top of this file).  It times the start of successive captures
  56 // and facilitates the processing of each through the stages of the
  57 // pipeline.
  58 class MEDIA_EXPORT ScreenCaptureDeviceCore
  59     : public base::SupportsWeakPtr<ScreenCaptureDeviceCore> {
  60  public:
  61   ScreenCaptureDeviceCore(scoped_ptr<VideoCaptureMachine> capture_machine);
  62   virtual ~ScreenCaptureDeviceCore();
  63
  64   // Asynchronous requests to change ScreenCaptureDeviceCore state.
  65   void AllocateAndStart(const VideoCaptureParams& params,
  66                         scoped_ptr<VideoCaptureDevice::Client> client);
  67   void StopAndDeAllocate();
  68
  69  private:
  70   // Flag indicating current state.
  71   enum State { kIdle, kCapturing, kError };
  72
  73   void TransitionStateTo(State next_state);
  74
  75   // Called back in response to StartCaptureMachine().  |success| is true if
  76   // capture machine succeeded to start.
  77   void CaptureStarted(bool success);
  78
  79   // Stops capturing and notifies client_ of an error state.
  80   void Error(const std::string& reason);
  81
  82   // Tracks that all activity occurs on the media stream manager's thread.
  83   base::ThreadChecker thread_checker_;
  84
  85   // Current lifecycle state.
  86   State state_;
  87
  88   // Tracks the CaptureMachine that's doing work on our behalf
  89   // on the device thread or UI thread.
  90   // This value should never be dereferenced by this class.
  91   scoped_ptr<VideoCaptureMachine> capture_machine_;
  92
  93   // Our thread-safe capture oracle which serves as the gateway to the video
  94   // capture pipeline. Besides the VideoCaptureDevice itself, it is the only
  95   // component of the system with direct access to |client_|.
  96   scoped_refptr<ThreadSafeCaptureOracle> oracle_proxy_;
  97
  98   DISALLOW_COPY_AND_ASSIGN(ScreenCaptureDeviceCore);
  99 };
 100
 101 }  // namespace media
 102
 103 #endif  // MEDIA_CAPTURE_SCREEN_CAPTURE_DEVICE_CORE_H_