remoting/host/capture_scheduler.h

   1 // Copyright (c) 2011 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 REMOTING_HOST_CAPTURE_SCHEDULER_H_
   6 #define REMOTING_HOST_CAPTURE_SCHEDULER_H_
   7
   8 #include "base/callback.h"
   9 #include "base/threading/thread_checker.h"
  10 #include "base/time/tick_clock.h"
  11 #include "base/time/time.h"
  12 #include "base/timer/timer.h"
  13 #include "remoting/base/running_average.h"
  14 #include "remoting/protocol/video_feedback_stub.h"
  15
  16 namespace remoting {
  17
  18 class VideoPacket;
  19
  20 // CaptureScheduler is used by the VideoFramePump to schedule frame capturer,
  21 // taking into account capture delay, encoder delay, network bandwidth, etc.
  22 // It implements VideoFeedbackStub to receive frame acknowledgments from the
  23 // client.
  24 //
  25 // It attempts to achieve the following goals when scheduling frames:
  26 //  - Keep round-trip latency as low a possible.
  27 //  - Parallelize capture, encode and transmission, to achieve frame rate as
  28 //    close to the target of 30fps as possible.
  29 //  - Limit CPU usage to 50%.
  30 class CaptureScheduler : public protocol::VideoFeedbackStub {
  31  public:
  32   explicit CaptureScheduler(const base::Closure& capture_closure);
  33   ~CaptureScheduler() override;
  34
  35   // Starts the scheduler.
  36   void Start();
  37
  38   // Pauses or unpauses the stream.
  39   void Pause(bool pause);
  40
  41   // Notifies the scheduler that a capture has been completed.
  42   void OnCaptureCompleted();
  43
  44   // Notifies the scheduler that a frame has been encoded. The scheduler can
  45   // change |packet| if necessary, e.g. set |frame_id|.
  46   void OnFrameEncoded(VideoPacket* packet);
  47
  48   // Notifies the scheduler that a frame has been sent.
  49   void OnFrameSent();
  50
  51   // VideoFeedbackStub interface.
  52   void ProcessVideoAck(scoped_ptr<VideoAck> video_ack) override;
  53
  54   // Sets minimum interval between frames.
  55   void set_minimum_interval(base::TimeDelta minimum_interval) {
  56     minimum_interval_ = minimum_interval;
  57   }
  58
  59   // Helper functions for tests.
  60   void SetTickClockForTest(scoped_ptr<base::TickClock> tick_clock);
  61   void SetTimerForTest(scoped_ptr<base::Timer> timer);
  62   void SetNumOfProcessorsForTest(int num_of_processors);
  63
  64  private:
  65   // Schedules |capture_timer_| to call CaptureNextFrame() at appropriate time.
  66   // Doesn't do anything if next frame cannot be captured yet (e.g. because
  67   // there are too many frames being processed).
  68   void ScheduleNextCapture();
  69
  70   // Called by |capture_timer_|. Calls |capture_closure_| to start capturing a
  71   // new frame.
  72   void CaptureNextFrame();
  73
  74   base::Closure capture_closure_;
  75
  76   scoped_ptr<base::TickClock> tick_clock_;
  77
  78   // Timer used to schedule CaptureNextFrame().
  79   scoped_ptr<base::Timer> capture_timer_;
  80
  81   // Minimum interval between frames that determines maximum possible framerate.
  82   base::TimeDelta minimum_interval_;
  83
  84   int num_of_processors_;
  85
  86   RunningAverage capture_time_;
  87   RunningAverage encode_time_;
  88
  89   // Number of frames pending encoding.
  90   int num_encoding_frames_;
  91
  92   // Number of outgoing frames for which we haven't received an acknowledgment.
  93   int num_unacknowledged_frames_;
  94
  95   // Set to true when capture is pending.
  96   bool capture_pending_;
  97
  98   // Time at which the last capture started. Used to schedule |capture_timer_|.
  99   base::TimeTicks last_capture_started_time_;
 100
 101   bool is_paused_;
 102
 103   // Frame ID to be assigned to the next outgoing video frame.
 104   uint32_t next_frame_id_;
 105
 106   base::ThreadChecker thread_checker_;
 107
 108   DISALLOW_COPY_AND_ASSIGN(CaptureScheduler);
 109 };
 110
 111 }  // namespace remoting
 112
 113 #endif  // REMOTING_HOST_CAPTURE_SCHEDULER_H_