remoting/host/capture_scheduler.cc

   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 #include "remoting/host/capture_scheduler.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/logging.h"
  10 #include "base/sys_info.h"
  11 #include "base/time/default_tick_clock.h"
  12 #include "base/time/time.h"
  13 #include "remoting/proto/video.pb.h"
  14
  15 namespace {
  16
  17 // Number of samples to average the most recent capture and encode time
  18 // over.
  19 const int kStatisticsWindow = 3;
  20
  21 // The hard limit is 30fps or 33ms per recording cycle.
  22 const int64 kDefaultMinimumIntervalMs = 33;
  23
  24 // Controls how much CPU time we can use for encode and capture.
  25 // Range of this value is between 0 to 1. 0 means using 0% of of all CPUs
  26 // available while 1 means using 100% of all CPUs available.
  27 const double kRecordingCpuConsumption = 0.5;
  28
  29 // Maximum number of captured frames in the encoding queue. Currently capturer
  30 // implementations do not allow to keep more than 2 DesktopFrame objects.
  31 static const int kMaxFramesInEncodingQueue = 2;
  32
  33 // Maximum number of unacknowledged frames. Ignored if the client doesn't
  34 // support ACKs. This value was chosen experimentally, using synthetic
  35 // performance tests (see ProtocolPerfTest), to maximize frame rate, while
  36 // keeping round-trip latency low.
  37 static const int kMaxUnacknowledgedFrames = 4;
  38
  39 }  // namespace
  40
  41 namespace remoting {
  42
  43 // We assume that the number of available cores is constant.
  44 CaptureScheduler::CaptureScheduler(const base::Closure& capture_closure)
  45     : capture_closure_(capture_closure),
  46       tick_clock_(new base::DefaultTickClock()),
  47       capture_timer_(new base::Timer(false, false)),
  48       minimum_interval_(
  49           base::TimeDelta::FromMilliseconds(kDefaultMinimumIntervalMs)),
  50       num_of_processors_(base::SysInfo::NumberOfProcessors()),
  51       capture_time_(kStatisticsWindow),
  52       encode_time_(kStatisticsWindow),
  53       num_encoding_frames_(0),
  54       num_unacknowledged_frames_(0),
  55       capture_pending_(false),
  56       is_paused_(false),
  57       next_frame_id_(0) {
  58   DCHECK(num_of_processors_);
  59 }
  60
  61 CaptureScheduler::~CaptureScheduler() {
  62 }
  63
  64 void CaptureScheduler::Start() {
  65   DCHECK(thread_checker_.CalledOnValidThread());
  66
  67   ScheduleNextCapture();
  68 }
  69
  70 void CaptureScheduler::Pause(bool pause) {
  71   DCHECK(thread_checker_.CalledOnValidThread());
  72
  73   if (is_paused_ != pause) {
  74     is_paused_ = pause;
  75
  76     if (is_paused_) {
  77       capture_timer_->Stop();
  78     } else {
  79       ScheduleNextCapture();
  80     }
  81   }
  82 }
  83
  84 void CaptureScheduler::OnCaptureCompleted() {
  85   DCHECK(thread_checker_.CalledOnValidThread());
  86
  87   capture_pending_ = false;
  88   capture_time_.Record(
  89       (tick_clock_->NowTicks() - last_capture_started_time_).InMilliseconds());
  90
  91   ++num_encoding_frames_;
  92
  93   ScheduleNextCapture();
  94 }
  95
  96 void CaptureScheduler::OnFrameEncoded(VideoPacket* packet) {
  97   DCHECK(thread_checker_.CalledOnValidThread());
  98
  99   // Set packet_id for the outgoing packet.
 100   packet->set_frame_id(next_frame_id_);
 101   ++next_frame_id_;
 102
 103   // Update internal stats.
 104   encode_time_.Record(packet->encode_time_ms());
 105
 106   --num_encoding_frames_;
 107   ++num_unacknowledged_frames_;
 108
 109   ScheduleNextCapture();
 110 }
 111
 112 void CaptureScheduler::OnFrameSent() {
 113   DCHECK(thread_checker_.CalledOnValidThread());
 114
 115   ScheduleNextCapture();
 116 }
 117
 118 void CaptureScheduler::ProcessVideoAck(scoped_ptr<VideoAck> video_ack) {
 119   DCHECK(thread_checker_.CalledOnValidThread());
 120
 121   --num_unacknowledged_frames_;
 122   DCHECK_GE(num_unacknowledged_frames_, 0);
 123
 124   ScheduleNextCapture();
 125 }
 126
 127 void CaptureScheduler::SetTickClockForTest(
 128     scoped_ptr<base::TickClock> tick_clock) {
 129   tick_clock_ = tick_clock.Pass();
 130 }
 131
 132 void CaptureScheduler::SetTimerForTest(scoped_ptr<base::Timer> timer) {
 133   capture_timer_ = timer.Pass();
 134 }
 135
 136 void CaptureScheduler::SetNumOfProcessorsForTest(int num_of_processors) {
 137   num_of_processors_ = num_of_processors;
 138 }
 139
 140 void CaptureScheduler::ScheduleNextCapture() {
 141   DCHECK(thread_checker_.CalledOnValidThread());
 142
 143   if (is_paused_ || capture_pending_ ||
 144       num_encoding_frames_ >= kMaxFramesInEncodingQueue) {
 145     return;
 146   }
 147
 148   if (num_encoding_frames_ + num_unacknowledged_frames_ >=
 149       kMaxUnacknowledgedFrames) {
 150     return;
 151   }
 152
 153   // Delay by an amount chosen such that if capture and encode times
 154   // continue to follow the averages, then we'll consume the target
 155   // fraction of CPU across all cores.
 156   base::TimeDelta delay =
 157       std::max(minimum_interval_,
 158                base::TimeDelta::FromMilliseconds(
 159                    (capture_time_.Average() + encode_time_.Average()) /
 160                    (kRecordingCpuConsumption * num_of_processors_)));
 161
 162   // Account for the time that has passed since the last capture.
 163   delay = std::max(base::TimeDelta(), delay - (tick_clock_->NowTicks() -
 164                                                last_capture_started_time_));
 165
 166   capture_timer_->Start(
 167       FROM_HERE, delay,
 168       base::Bind(&CaptureScheduler::CaptureNextFrame, base::Unretained(this)));
 169 }
 170
 171 void CaptureScheduler::CaptureNextFrame() {
 172   DCHECK(thread_checker_.CalledOnValidThread());
 173   DCHECK(!is_paused_);
 174   DCHECK(!capture_pending_);
 175
 176   capture_pending_ = true;
 177   last_capture_started_time_ = tick_clock_->NowTicks();
 178   capture_closure_.Run();
 179 }
 180
 181 }  // namespace remoting