remoting/host/video_scheduler.h

   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 #ifndef REMOTING_HOST_VIDEO_SCHEDULER_H_
   6 #define REMOTING_HOST_VIDEO_SCHEDULER_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/time/time.h"
  14 #include "base/timer/timer.h"
  15 #include "remoting/codec/video_encoder.h"
  16 #include "remoting/host/capture_scheduler.h"
  17 #include "remoting/proto/video.pb.h"
  18 #include "third_party/webrtc/modules/desktop_capture/desktop_capturer.h"
  19 #include "third_party/webrtc/modules/desktop_capture/mouse_cursor_monitor.h"
  20
  21 namespace base {
  22 class SingleThreadTaskRunner;
  23 }  // namespace base
  24
  25 namespace media {
  26 class DesktopCapturer;
  27 }  // namespace media
  28
  29 namespace remoting {
  30
  31 class CursorShapeInfo;
  32
  33 namespace protocol {
  34 class CursorShapeInfo;
  35 class CursorShapeStub;
  36 class VideoStub;
  37 }  // namespace protocol
  38
  39 // Class responsible for scheduling frame captures from a
  40 // webrtc::DesktopCapturer, delivering them to a VideoEncoder to encode, and
  41 // finally passing the encoded video packets to the specified VideoStub to send
  42 // on the network.
  43 //
  44 // THREADING
  45 //
  46 // This class is supplied TaskRunners to use for capture, encode and network
  47 // operations.  Capture, encode and network transmission tasks are interleaved
  48 // as illustrated below:
  49 //
  50 // |       CAPTURE       ENCODE     NETWORK
  51 // |    .............
  52 // |    .  Capture  .
  53 // |    .............
  54 // |                  ............
  55 // |                  .          .
  56 // |    ............. .          .
  57 // |    .  Capture  . .  Encode  .
  58 // |    ............. .          .
  59 // |                  .          .
  60 // |                  ............
  61 // |    ............. ............ ..........
  62 // |    .  Capture  . .          . .  Send  .
  63 // |    ............. .          . ..........
  64 // |                  .  Encode  .
  65 // |                  .          .
  66 // |                  .          .
  67 // |                  ............
  68 // | Time
  69 // v
  70 //
  71 // VideoScheduler would ideally schedule captures so as to saturate the slowest
  72 // of the capture, encode and network processes.  However, it also needs to
  73 // rate-limit captures to avoid overloading the host system, either by consuming
  74 // too much CPU, or hogging the host's graphics subsystem.
  75
  76 class VideoScheduler : public base::RefCountedThreadSafe<VideoScheduler>,
  77                        public webrtc::DesktopCapturer::Callback,
  78                        public webrtc::MouseCursorMonitor::Callback {
  79  public:
  80   // Enables timestamps for generated frames. Used for testing.
  81   static void EnableTimestampsForTests();
  82
  83   // Creates a VideoScheduler running capture, encode and network tasks on the
  84   // supplied TaskRunners.  Video and cursor shape updates will be pumped to
  85   // |video_stub| and |client_stub|, which must remain valid until Stop() is
  86   // called. |capturer| is used to capture frames.
  87   VideoScheduler(
  88       scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner,
  89       scoped_refptr<base::SingleThreadTaskRunner> encode_task_runner,
  90       scoped_refptr<base::SingleThreadTaskRunner> network_task_runner,
  91       scoped_ptr<webrtc::DesktopCapturer> capturer,
  92       scoped_ptr<webrtc::MouseCursorMonitor> mouse_cursor_monitor,
  93       scoped_ptr<VideoEncoder> encoder,
  94       protocol::CursorShapeStub* cursor_stub,
  95       protocol::VideoStub* video_stub);
  96
  97   // webrtc::DesktopCapturer::Callback implementation.
  98   webrtc::SharedMemory* CreateSharedMemory(size_t size) override;
  99   void OnCaptureCompleted(webrtc::DesktopFrame* frame) override;
 100
 101   // webrtc::MouseCursorMonitor::Callback implementation.
 102   void OnMouseCursor(webrtc::MouseCursor* mouse_cursor) override;
 103   void OnMouseCursorPosition(webrtc::MouseCursorMonitor::CursorState state,
 104                              const webrtc::DesktopVector& position) override;
 105
 106   // Starts scheduling frame captures.
 107   void Start();
 108
 109   // Stop scheduling frame captures. This object cannot be re-used once
 110   // it has been stopped.
 111   void Stop();
 112
 113   // Pauses or resumes scheduling of frame captures.  Pausing/resuming captures
 114   // only affects capture scheduling and does not stop/start the capturer.
 115   void Pause(bool pause);
 116
 117   // Updates the sequence number embedded in VideoPackets.
 118   // Sequence numbers are used for performance measurements.
 119   void UpdateSequenceNumber(int64 sequence_number);
 120
 121   // Sets whether the video encoder should be requested to encode losslessly,
 122   // or to use a lossless color space (typically requiring higher bandwidth).
 123   void SetLosslessEncode(bool want_lossless);
 124   void SetLosslessColor(bool want_lossless);
 125
 126  private:
 127   friend class base::RefCountedThreadSafe<VideoScheduler>;
 128   ~VideoScheduler() override;
 129
 130   // Capturer thread ----------------------------------------------------------
 131
 132   // Starts the capturer on the capture thread.
 133   void StartOnCaptureThread();
 134
 135   // Stops scheduling frame captures on the capture thread.
 136   void StopOnCaptureThread();
 137
 138   // Schedules the next call to CaptureNextFrame.
 139   void ScheduleNextCapture();
 140
 141   // Starts the next frame capture, unless there are already too many pending.
 142   void CaptureNextFrame();
 143
 144   // Called when a frame capture has been encoded & sent to the client.
 145   void FrameCaptureCompleted();
 146
 147   // Network thread -----------------------------------------------------------
 148
 149   // Send |packet| to the client, unless we are in the process of stopping.
 150   void SendVideoPacket(scoped_ptr<VideoPacket> packet);
 151
 152   // Callback passed to |video_stub_| for the last packet in each frame, to
 153   // rate-limit frame captures to network throughput.
 154   void OnVideoPacketSent();
 155
 156   // Called by |keep_alive_timer_|.
 157   void SendKeepAlivePacket();
 158
 159   // Callback for |video_stub_| called after a keep-alive packet is sent.
 160   void OnKeepAlivePacketSent();
 161
 162   // Send updated cursor shape to client.
 163   void SendCursorShape(scoped_ptr<protocol::CursorShapeInfo> cursor_shape);
 164
 165   // Encoder thread -----------------------------------------------------------
 166
 167   // Encode a frame, passing generated VideoPackets to SendVideoPacket().
 168   void EncodeFrame(scoped_ptr<webrtc::DesktopFrame> frame,
 169                    int64 sequence_number,
 170                    base::TimeTicks timestamp);
 171
 172   void EncodedDataAvailableCallback(int64 sequence_number,
 173                                     scoped_ptr<VideoPacket> packet);
 174
 175   // Task runners used by this class.
 176   scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner_;
 177   scoped_refptr<base::SingleThreadTaskRunner> encode_task_runner_;
 178   scoped_refptr<base::SingleThreadTaskRunner> network_task_runner_;
 179
 180   // Used to capture frames. Always accessed on the capture thread.
 181   scoped_ptr<webrtc::DesktopCapturer> capturer_;
 182
 183   // Used to capture mouse cursor shapes. Always accessed on the capture thread.
 184   scoped_ptr<webrtc::MouseCursorMonitor> mouse_cursor_monitor_;
 185
 186   // Used to encode captured frames. Always accessed on the encode thread.
 187   scoped_ptr<VideoEncoder> encoder_;
 188
 189   // Interfaces through which video frames and cursor shapes are passed to the
 190   // client. These members are always accessed on the network thread.
 191   protocol::CursorShapeStub* cursor_stub_;
 192   protocol::VideoStub* video_stub_;
 193
 194   // Timer used to schedule CaptureNextFrame().
 195   scoped_ptr<base::OneShotTimer<VideoScheduler> > capture_timer_;
 196
 197   // Timer used to ensure that we send empty keep-alive frames to the client
 198   // even when the video stream is paused or encoder is busy.
 199   scoped_ptr<base::DelayTimer<VideoScheduler> > keep_alive_timer_;
 200
 201   // The number of frames being processed, i.e. frames that we are currently
 202   // capturing, encoding or sending. The value is capped at 2 to minimize
 203   // latency.
 204   int pending_frames_;
 205
 206   // Set when the capturer is capturing a frame.
 207   bool capture_pending_;
 208
 209   // True if the previous scheduled capture was skipped.
 210   bool did_skip_frame_;
 211
 212   // True if capture of video frames is paused.
 213   bool is_paused_;
 214
 215   // Number updated by the caller to trace performance.
 216   int64 sequence_number_;
 217
 218   // An object to schedule capturing.
 219   CaptureScheduler scheduler_;
 220
 221   DISALLOW_COPY_AND_ASSIGN(VideoScheduler);
 222 };
 223
 224 }  // namespace remoting
 225
 226 #endif  // REMOTING_HOST_VIDEO_SCHEDULER_H_