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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "remoting/protocol/capture_scheduler.h"
#include <algorithm>
#include <utility>
#include "base/check_op.h"
#include "base/functional/bind.h"
#include "base/system/sys_info.h"
#include "base/time/default_tick_clock.h"
#include "base/time/time.h"
#include "remoting/proto/video.pb.h"
namespace {
// Number of samples to average the most recent capture and encode time
// over.
const int kStatisticsWindow = 3;
// The hard limit is 30fps or 33ms per recording cycle.
const int64_t kDefaultMinimumIntervalMs = 33;
// Controls how much CPU time we can use for encode and capture.
// Range of this value is between 0 to 1. 0 means using 0% of of all CPUs
// available while 1 means using 100% of all CPUs available.
const double kRecordingCpuConsumption = 0.5;
// Maximum number of captured frames in the encoding queue. Currently capturer
// implementations do not allow to keep more than 2 DesktopFrame objects.
static const int kMaxFramesInEncodingQueue = 2;
// Maximum number of unacknowledged frames. Ignored if the client doesn't
// support ACKs. This value was chosen experimentally, using synthetic
// performance tests (see ProtocolPerfTest), to maximize frame rate, while
// keeping round-trip latency low.
static const int kMaxUnacknowledgedFrames = 4;
} // namespace
namespace remoting::protocol {
// We assume that the number of available cores is constant.
CaptureScheduler::CaptureScheduler(
const base::RepeatingClosure& capture_closure)
: capture_closure_(capture_closure),
tick_clock_(base::DefaultTickClock::GetInstance()),
capture_timer_(new base::OneShotTimer()),
minimum_interval_(base::Milliseconds(kDefaultMinimumIntervalMs)),
num_of_processors_(base::SysInfo::NumberOfProcessors()),
capture_time_(kStatisticsWindow),
encode_time_(kStatisticsWindow),
num_encoding_frames_(0),
num_unacknowledged_frames_(0),
capture_pending_(false),
is_paused_(false),
next_frame_id_(0) {
DCHECK(num_of_processors_);
}
CaptureScheduler::~CaptureScheduler() {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
}
void CaptureScheduler::Start() {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
ScheduleNextCapture();
}
void CaptureScheduler::Pause(bool pause) {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
if (is_paused_ != pause) {
is_paused_ = pause;
if (is_paused_) {
capture_timer_->Stop();
} else {
ScheduleNextCapture();
}
}
}
void CaptureScheduler::OnCaptureCompleted() {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
capture_pending_ = false;
capture_time_.Record(
(tick_clock_->NowTicks() - last_capture_started_time_).InMilliseconds());
++num_encoding_frames_;
ScheduleNextCapture();
}
void CaptureScheduler::OnFrameEncoded(VideoPacket* packet) {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
// Set packet_id for the outgoing packet.
packet->set_frame_id(next_frame_id_);
++next_frame_id_;
// Update internal stats.
encode_time_.Record(packet->encode_time_ms());
--num_encoding_frames_;
++num_unacknowledged_frames_;
ScheduleNextCapture();
}
void CaptureScheduler::OnFrameSent() {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
ScheduleNextCapture();
}
void CaptureScheduler::ProcessVideoAck(std::unique_ptr<VideoAck> video_ack) {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
--num_unacknowledged_frames_;
DCHECK_GE(num_unacknowledged_frames_, 0);
ScheduleNextCapture();
}
void CaptureScheduler::SetTickClockForTest(const base::TickClock* tick_clock) {
tick_clock_ = tick_clock;
}
void CaptureScheduler::SetTimerForTest(
std::unique_ptr<base::OneShotTimer> timer) {
capture_timer_ = std::move(timer);
}
void CaptureScheduler::SetNumOfProcessorsForTest(int num_of_processors) {
num_of_processors_ = num_of_processors;
}
void CaptureScheduler::ScheduleNextCapture() {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
if (is_paused_ || capture_pending_ ||
num_encoding_frames_ >= kMaxFramesInEncodingQueue) {
return;
}
if (num_encoding_frames_ + num_unacknowledged_frames_ >=
kMaxUnacknowledgedFrames) {
return;
}
// Delay by an amount chosen such that if capture and encode times
// continue to follow the averages, then we'll consume the target
// fraction of CPU across all cores.
base::TimeDelta delay = std::max(
minimum_interval_,
base::Milliseconds((capture_time_.Average() + encode_time_.Average()) /
(kRecordingCpuConsumption * num_of_processors_)));
// Account for the time that has passed since the last capture.
delay = std::max(base::TimeDelta(), delay - (tick_clock_->NowTicks() -
last_capture_started_time_));
capture_timer_->Start(FROM_HERE, delay,
base::BindOnce(&CaptureScheduler::CaptureNextFrame,
base::Unretained(this)));
}
void CaptureScheduler::CaptureNextFrame() {
DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
DCHECK(!is_paused_);
DCHECK(!capture_pending_);
capture_pending_ = true;
last_capture_started_time_ = tick_clock_->NowTicks();
capture_closure_.Run();
}
} // namespace remoting::protocol
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