modules/congestion_controller/probe_controller.cc - src/webrtc - Git at Google

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "webrtc/modules/congestion_controller/probe_controller.h"

 #include <algorithm>
 #include <initializer_list>

 #include "webrtc/rtc_base/logging.h"
 #include "webrtc/rtc_base/safe_conversions.h"
 #include "webrtc/system_wrappers/include/field_trial.h"
 #include "webrtc/system_wrappers/include/metrics.h"

 namespace webrtc {

 namespace {
 // Maximum waiting time from the time of initiating probing to getting
 // the measured results back.
 constexpr int64_t kMaxWaitingTimeForProbingResultMs = 1000;

 // Value of |min_bitrate_to_probe_further_bps_| that indicates
 // further probing is disabled.
 constexpr int kExponentialProbingDisabled = 0;

 // Default probing bitrate limit. Applied only when the application didn't
 // specify max bitrate.
 constexpr int64_t kDefaultMaxProbingBitrateBps = 5000000;

 // Interval between probes when ALR periodic probing is enabled.
 constexpr int64_t kAlrPeriodicProbingIntervalMs = 5000;

 // Minimum probe bitrate percentage to probe further for repeated probes,
 // relative to the previous probe. For example, if 1Mbps probe results in
 // 80kbps, then we'll probe again at 1.6Mbps. In that case second probe won't be
 // sent if we get 600kbps from the first one.
 constexpr int kRepeatedProbeMinPercentage = 70;

 // If the bitrate drops to a factor |kBitrateDropThreshold| or lower
 // and we recover within |kBitrateDropTimeoutMs|, then we'll send
 // a probe at a fraction |kProbeFractionAfterDrop| of the original bitrate.
 constexpr double kBitrateDropThreshold = 0.66;
 constexpr int kBitrateDropTimeoutMs = 5000;
 constexpr double kProbeFractionAfterDrop = 0.85;

 // Timeout for probing after leaving ALR. If the bitrate drops significantly,
 // (as determined by the delay based estimator) and we leave ALR, then we will
 // send a probe if we recover within |kLeftAlrTimeoutMs| ms.
 constexpr int kAlrEndedTimeoutMs = 3000;

 // The expected uncertainty of probe result (as a fraction of the target probe
 // This is a limit on how often probing can be done when there is a BW
 // drop detected in ALR.
 constexpr int64_t kMinTimeBetweenAlrProbesMs = 5000;

 // bitrate). Used to avoid probing if the probe bitrate is close to our current
 // estimate.
 constexpr double kProbeUncertainty = 0.05;

 // Use probing to recover faster after large bitrate estimate drops.
 constexpr char kBweRapidRecoveryExperiment[] =
     "WebRTC-BweRapidRecoveryExperiment";

 }  // namespace

 ProbeController::ProbeController(PacedSender* pacer, const Clock* clock)
     : pacer_(pacer), clock_(clock), enable_periodic_alr_probing_(false) {
   Reset();
   in_rapid_recovery_experiment_ = webrtc::field_trial::FindFullName(
                                       kBweRapidRecoveryExperiment) == "Enabled";
 }

 void ProbeController::SetBitrates(int64_t min_bitrate_bps,
                                   int64_t start_bitrate_bps,
                                   int64_t max_bitrate_bps) {
   rtc::CritScope cs(&critsect_);

   if (start_bitrate_bps > 0)  {
     start_bitrate_bps_ = start_bitrate_bps;
     estimated_bitrate_bps_ = start_bitrate_bps;
   } else if (start_bitrate_bps_ == 0) {
     start_bitrate_bps_ = min_bitrate_bps;
   }

   // The reason we use the variable |old_max_bitrate_pbs| is because we
   // need to set |max_bitrate_bps_| before we call InitiateProbing.
   int64_t old_max_bitrate_bps = max_bitrate_bps_;
   max_bitrate_bps_ = max_bitrate_bps;

   switch (state_) {
     case State::kInit:
       if (network_state_ == kNetworkUp)
         InitiateExponentialProbing();
       break;

     case State::kWaitingForProbingResult:
       break;

     case State::kProbingComplete:
       // If the new max bitrate is higher than the old max bitrate and the
       // estimate is lower than the new max bitrate then initiate probing.
       if (estimated_bitrate_bps_ != 0 &&
           old_max_bitrate_bps < max_bitrate_bps_ &&
           estimated_bitrate_bps_ < max_bitrate_bps_) {
         // The assumption is that if we jump more than 20% in the bandwidth
         // estimate or if the bandwidth estimate is within 90% of the new
         // max bitrate then the probing attempt was successful.
         mid_call_probing_succcess_threshold_ =
             std::min(estimated_bitrate_bps_ * 1.2, max_bitrate_bps_ * 0.9);
         mid_call_probing_waiting_for_result_ = true;
         mid_call_probing_bitrate_bps_ = max_bitrate_bps_;

         RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.MidCallProbing.Initiated",
                                    max_bitrate_bps_ / 1000);

         InitiateProbing(clock_->TimeInMilliseconds(), {max_bitrate_bps}, false);
       }
       break;
   }
 }

 void ProbeController::OnNetworkStateChanged(NetworkState network_state) {
   rtc::CritScope cs(&critsect_);
   network_state_ = network_state;
   if (network_state_ == kNetworkUp && state_ == State::kInit)
     InitiateExponentialProbing();
 }

 void ProbeController::InitiateExponentialProbing() {
   RTC_DCHECK(network_state_ == kNetworkUp);
   RTC_DCHECK(state_ == State::kInit);
   RTC_DCHECK_GT(start_bitrate_bps_, 0);

   // When probing at 1.8 Mbps ( 6x 300), this represents a threshold of
   // 1.2 Mbps to continue probing.
   InitiateProbing(clock_->TimeInMilliseconds(),
                   {3 * start_bitrate_bps_, 6 * start_bitrate_bps_}, true);
 }

 void ProbeController::SetEstimatedBitrate(int64_t bitrate_bps) {
   rtc::CritScope cs(&critsect_);
   int64_t now_ms = clock_->TimeInMilliseconds();

   if (mid_call_probing_waiting_for_result_ &&
       bitrate_bps >= mid_call_probing_succcess_threshold_) {
     RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.MidCallProbing.Success",
                                mid_call_probing_bitrate_bps_ / 1000);
     RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.MidCallProbing.ProbedKbps",
                                bitrate_bps / 1000);
     mid_call_probing_waiting_for_result_ = false;
   }

   if (state_ == State::kWaitingForProbingResult) {
     // Continue probing if probing results indicate channel has greater
     // capacity.
     LOG(LS_INFO) << "Measured bitrate: " << bitrate_bps
                  << " Minimum to probe further: "
                  << min_bitrate_to_probe_further_bps_;

     if (min_bitrate_to_probe_further_bps_ != kExponentialProbingDisabled &&
         bitrate_bps > min_bitrate_to_probe_further_bps_) {
       // Double the probing bitrate.
       InitiateProbing(now_ms, {2 * bitrate_bps}, true);
     }
   }

   if (bitrate_bps < kBitrateDropThreshold * estimated_bitrate_bps_) {
     time_of_last_large_drop_ms_ = now_ms;
     bitrate_before_last_large_drop_bps_ = estimated_bitrate_bps_;
   }

   estimated_bitrate_bps_ = bitrate_bps;
 }

 void ProbeController::EnablePeriodicAlrProbing(bool enable) {
   rtc::CritScope cs(&critsect_);
   enable_periodic_alr_probing_ = enable;
 }

 void ProbeController::SetAlrEndedTimeMs(int64_t alr_end_time_ms) {
   rtc::CritScope cs(&critsect_);
   alr_end_time_ms_.emplace(alr_end_time_ms);
 }

 void ProbeController::RequestProbe() {
   int64_t now_ms = clock_->TimeInMilliseconds();
   rtc::CritScope cs(&critsect_);
   // Called once we have returned to normal state after a large drop in
   // estimated bandwidth. The current response is to initiate a single probe
   // session (if not already probing) at the previous bitrate.
   //
   // If the probe session fails, the assumption is that this drop was a
   // real one from a competing flow or a network change.
   bool in_alr = pacer_->GetApplicationLimitedRegionStartTime().has_value();
   bool alr_ended_recently =
       (alr_end_time_ms_.has_value() &&
        now_ms - alr_end_time_ms_.value() < kAlrEndedTimeoutMs);
   if (in_alr || alr_ended_recently || in_rapid_recovery_experiment_) {
     if (state_ == State::kProbingComplete) {
       uint32_t suggested_probe_bps =
           kProbeFractionAfterDrop * bitrate_before_last_large_drop_bps_;
       uint32_t min_expected_probe_result_bps =
           (1 - kProbeUncertainty) * suggested_probe_bps;
       int64_t time_since_drop_ms = now_ms - time_of_last_large_drop_ms_;
       int64_t time_since_probe_ms = now_ms - last_bwe_drop_probing_time_ms_;
       if (min_expected_probe_result_bps > estimated_bitrate_bps_ &&
           time_since_drop_ms < kBitrateDropTimeoutMs &&
           time_since_probe_ms > kMinTimeBetweenAlrProbesMs) {
         LOG(LS_INFO) << "Detected big bandwidth drop, start probing.";
         // Track how often we probe in response to bandwidth drop in ALR.
         RTC_HISTOGRAM_COUNTS_10000(
             "WebRTC.BWE.BweDropProbingIntervalInS",
             (now_ms - last_bwe_drop_probing_time_ms_) / 1000);
         InitiateProbing(now_ms, {suggested_probe_bps}, false);
         last_bwe_drop_probing_time_ms_ = now_ms;
       }
     }
   }
 }

 void ProbeController::Reset() {
   rtc::CritScope cs(&critsect_);
   network_state_ = kNetworkUp;
   state_ = State::kInit;
   min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
   time_last_probing_initiated_ms_ = 0;
   estimated_bitrate_bps_ = 0;
   start_bitrate_bps_ = 0;
   max_bitrate_bps_ = 0;
   int64_t now_ms = clock_->TimeInMilliseconds();
   last_bwe_drop_probing_time_ms_ = now_ms;
   alr_end_time_ms_.reset();
   mid_call_probing_waiting_for_result_ = false;
   time_of_last_large_drop_ms_ = now_ms;
   bitrate_before_last_large_drop_bps_ = 0;
 }

 void ProbeController::Process() {
   rtc::CritScope cs(&critsect_);

   int64_t now_ms = clock_->TimeInMilliseconds();

   if (now_ms - time_last_probing_initiated_ms_ >
       kMaxWaitingTimeForProbingResultMs) {
     mid_call_probing_waiting_for_result_ = false;

     if (state_ == State::kWaitingForProbingResult) {
       LOG(LS_INFO) << "kWaitingForProbingResult: timeout";
       state_ = State::kProbingComplete;
       min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
     }
   }

   if (state_ != State::kProbingComplete || !enable_periodic_alr_probing_)
     return;

   // Probe bandwidth periodically when in ALR state.
   rtc::Optional<int64_t> alr_start_time =
       pacer_->GetApplicationLimitedRegionStartTime();
   if (alr_start_time && estimated_bitrate_bps_ > 0) {
     int64_t next_probe_time_ms =
         std::max(*alr_start_time, time_last_probing_initiated_ms_) +
         kAlrPeriodicProbingIntervalMs;
     if (now_ms >= next_probe_time_ms) {
       InitiateProbing(now_ms, {estimated_bitrate_bps_ * 2}, true);
     }
   }
 }

 void ProbeController::InitiateProbing(
     int64_t now_ms,
     std::initializer_list<int64_t> bitrates_to_probe,
     bool probe_further) {
   for (int64_t bitrate : bitrates_to_probe) {
     RTC_DCHECK_GT(bitrate, 0);
     int64_t max_probe_bitrate_bps =
         max_bitrate_bps_ > 0 ? max_bitrate_bps_ : kDefaultMaxProbingBitrateBps;
     if (bitrate > max_probe_bitrate_bps) {
       bitrate = max_probe_bitrate_bps;
       probe_further = false;
     }
     pacer_->CreateProbeCluster(rtc::dchecked_cast<int>(bitrate));
   }
   time_last_probing_initiated_ms_ = now_ms;
   if (probe_further) {
     state_ = State::kWaitingForProbingResult;
     min_bitrate_to_probe_further_bps_ =
         (*(bitrates_to_probe.end() - 1)) * kRepeatedProbeMinPercentage / 100;
   } else {
     state_ = State::kProbingComplete;
     min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
   }
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "webrtc/modules/congestion_controller/probe_controller.h"

	#include <algorithm>
	#include <initializer_list>

	#include "webrtc/rtc_base/logging.h"
	#include "webrtc/rtc_base/safe_conversions.h"
	#include "webrtc/system_wrappers/include/field_trial.h"
	#include "webrtc/system_wrappers/include/metrics.h"

	namespace webrtc {

	namespace {
	// Maximum waiting time from the time of initiating probing to getting
	// the measured results back.
	constexpr int64_t kMaxWaitingTimeForProbingResultMs = 1000;

	// Value of \|min_bitrate_to_probe_further_bps_\| that indicates
	// further probing is disabled.
	constexpr int kExponentialProbingDisabled = 0;

	// Default probing bitrate limit. Applied only when the application didn't
	// specify max bitrate.
	constexpr int64_t kDefaultMaxProbingBitrateBps = 5000000;

	// Interval between probes when ALR periodic probing is enabled.
	constexpr int64_t kAlrPeriodicProbingIntervalMs = 5000;

	// Minimum probe bitrate percentage to probe further for repeated probes,
	// relative to the previous probe. For example, if 1Mbps probe results in
	// 80kbps, then we'll probe again at 1.6Mbps. In that case second probe won't be
	// sent if we get 600kbps from the first one.
	constexpr int kRepeatedProbeMinPercentage = 70;

	// If the bitrate drops to a factor \|kBitrateDropThreshold\| or lower
	// and we recover within \|kBitrateDropTimeoutMs\|, then we'll send
	// a probe at a fraction \|kProbeFractionAfterDrop\| of the original bitrate.
	constexpr double kBitrateDropThreshold = 0.66;
	constexpr int kBitrateDropTimeoutMs = 5000;
	constexpr double kProbeFractionAfterDrop = 0.85;

	// Timeout for probing after leaving ALR. If the bitrate drops significantly,
	// (as determined by the delay based estimator) and we leave ALR, then we will
	// send a probe if we recover within \|kLeftAlrTimeoutMs\| ms.
	constexpr int kAlrEndedTimeoutMs = 3000;

	// The expected uncertainty of probe result (as a fraction of the target probe
	// This is a limit on how often probing can be done when there is a BW
	// drop detected in ALR.
	constexpr int64_t kMinTimeBetweenAlrProbesMs = 5000;

	// bitrate). Used to avoid probing if the probe bitrate is close to our current
	// estimate.
	constexpr double kProbeUncertainty = 0.05;

	// Use probing to recover faster after large bitrate estimate drops.
	constexpr char kBweRapidRecoveryExperiment[] =
	"WebRTC-BweRapidRecoveryExperiment";

	} // namespace

	ProbeController::ProbeController(PacedSender* pacer, const Clock* clock)
	: pacer_(pacer), clock_(clock), enable_periodic_alr_probing_(false) {
	Reset();
	in_rapid_recovery_experiment_ = webrtc::field_trial::FindFullName(
	kBweRapidRecoveryExperiment) == "Enabled";
	}

	void ProbeController::SetBitrates(int64_t min_bitrate_bps,
	int64_t start_bitrate_bps,
	int64_t max_bitrate_bps) {
	rtc::CritScope cs(&critsect_);

	if (start_bitrate_bps > 0) {
	start_bitrate_bps_ = start_bitrate_bps;
	estimated_bitrate_bps_ = start_bitrate_bps;
	} else if (start_bitrate_bps_ == 0) {
	start_bitrate_bps_ = min_bitrate_bps;
	}

	// The reason we use the variable \|old_max_bitrate_pbs\| is because we
	// need to set \|max_bitrate_bps_\| before we call InitiateProbing.
	int64_t old_max_bitrate_bps = max_bitrate_bps_;
	max_bitrate_bps_ = max_bitrate_bps;

	switch (state_) {
	case State::kInit:
	if (network_state_ == kNetworkUp)
	InitiateExponentialProbing();
	break;

	case State::kWaitingForProbingResult:
	break;

	case State::kProbingComplete:
	// If the new max bitrate is higher than the old max bitrate and the
	// estimate is lower than the new max bitrate then initiate probing.
	if (estimated_bitrate_bps_ != 0 &&
	old_max_bitrate_bps < max_bitrate_bps_ &&
	estimated_bitrate_bps_ < max_bitrate_bps_) {
	// The assumption is that if we jump more than 20% in the bandwidth
	// estimate or if the bandwidth estimate is within 90% of the new
	// max bitrate then the probing attempt was successful.
	mid_call_probing_succcess_threshold_ =
	std::min(estimated_bitrate_bps_ * 1.2, max_bitrate_bps_ * 0.9);
	mid_call_probing_waiting_for_result_ = true;
	mid_call_probing_bitrate_bps_ = max_bitrate_bps_;

	RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.MidCallProbing.Initiated",
	max_bitrate_bps_ / 1000);

	InitiateProbing(clock_->TimeInMilliseconds(), {max_bitrate_bps}, false);
	}
	break;
	}
	}

	void ProbeController::OnNetworkStateChanged(NetworkState network_state) {
	rtc::CritScope cs(&critsect_);
	network_state_ = network_state;
	if (network_state_ == kNetworkUp && state_ == State::kInit)
	InitiateExponentialProbing();
	}

	void ProbeController::InitiateExponentialProbing() {
	RTC_DCHECK(network_state_ == kNetworkUp);
	RTC_DCHECK(state_ == State::kInit);
	RTC_DCHECK_GT(start_bitrate_bps_, 0);

	// When probing at 1.8 Mbps ( 6x 300), this represents a threshold of
	// 1.2 Mbps to continue probing.
	InitiateProbing(clock_->TimeInMilliseconds(),
	{3 * start_bitrate_bps_, 6 * start_bitrate_bps_}, true);
	}

	void ProbeController::SetEstimatedBitrate(int64_t bitrate_bps) {
	rtc::CritScope cs(&critsect_);
	int64_t now_ms = clock_->TimeInMilliseconds();

	if (mid_call_probing_waiting_for_result_ &&
	bitrate_bps >= mid_call_probing_succcess_threshold_) {
	RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.MidCallProbing.Success",
	mid_call_probing_bitrate_bps_ / 1000);
	RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.MidCallProbing.ProbedKbps",
	bitrate_bps / 1000);
	mid_call_probing_waiting_for_result_ = false;
	}

	if (state_ == State::kWaitingForProbingResult) {
	// Continue probing if probing results indicate channel has greater
	// capacity.
	LOG(LS_INFO) << "Measured bitrate: " << bitrate_bps
	<< " Minimum to probe further: "
	<< min_bitrate_to_probe_further_bps_;

	if (min_bitrate_to_probe_further_bps_ != kExponentialProbingDisabled &&
	bitrate_bps > min_bitrate_to_probe_further_bps_) {
	// Double the probing bitrate.
	InitiateProbing(now_ms, {2 * bitrate_bps}, true);
	}
	}

	if (bitrate_bps < kBitrateDropThreshold * estimated_bitrate_bps_) {
	time_of_last_large_drop_ms_ = now_ms;
	bitrate_before_last_large_drop_bps_ = estimated_bitrate_bps_;
	}

	estimated_bitrate_bps_ = bitrate_bps;
	}

	void ProbeController::EnablePeriodicAlrProbing(bool enable) {
	rtc::CritScope cs(&critsect_);
	enable_periodic_alr_probing_ = enable;
	}

	void ProbeController::SetAlrEndedTimeMs(int64_t alr_end_time_ms) {
	rtc::CritScope cs(&critsect_);
	alr_end_time_ms_.emplace(alr_end_time_ms);
	}

	void ProbeController::RequestProbe() {
	int64_t now_ms = clock_->TimeInMilliseconds();
	rtc::CritScope cs(&critsect_);
	// Called once we have returned to normal state after a large drop in
	// estimated bandwidth. The current response is to initiate a single probe
	// session (if not already probing) at the previous bitrate.
	//
	// If the probe session fails, the assumption is that this drop was a
	// real one from a competing flow or a network change.
	bool in_alr = pacer_->GetApplicationLimitedRegionStartTime().has_value();
	bool alr_ended_recently =
	(alr_end_time_ms_.has_value() &&
	now_ms - alr_end_time_ms_.value() < kAlrEndedTimeoutMs);
	if (in_alr \|\| alr_ended_recently \|\| in_rapid_recovery_experiment_) {
	if (state_ == State::kProbingComplete) {
	uint32_t suggested_probe_bps =
	kProbeFractionAfterDrop * bitrate_before_last_large_drop_bps_;
	uint32_t min_expected_probe_result_bps =
	(1 - kProbeUncertainty) * suggested_probe_bps;
	int64_t time_since_drop_ms = now_ms - time_of_last_large_drop_ms_;
	int64_t time_since_probe_ms = now_ms - last_bwe_drop_probing_time_ms_;
	if (min_expected_probe_result_bps > estimated_bitrate_bps_ &&
	time_since_drop_ms < kBitrateDropTimeoutMs &&
	time_since_probe_ms > kMinTimeBetweenAlrProbesMs) {
	LOG(LS_INFO) << "Detected big bandwidth drop, start probing.";
	// Track how often we probe in response to bandwidth drop in ALR.
	RTC_HISTOGRAM_COUNTS_10000(
	"WebRTC.BWE.BweDropProbingIntervalInS",
	(now_ms - last_bwe_drop_probing_time_ms_) / 1000);
	InitiateProbing(now_ms, {suggested_probe_bps}, false);
	last_bwe_drop_probing_time_ms_ = now_ms;
	}
	}
	}
	}

	void ProbeController::Reset() {
	rtc::CritScope cs(&critsect_);
	network_state_ = kNetworkUp;
	state_ = State::kInit;
	min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
	time_last_probing_initiated_ms_ = 0;
	estimated_bitrate_bps_ = 0;
	start_bitrate_bps_ = 0;
	max_bitrate_bps_ = 0;
	int64_t now_ms = clock_->TimeInMilliseconds();
	last_bwe_drop_probing_time_ms_ = now_ms;
	alr_end_time_ms_.reset();
	mid_call_probing_waiting_for_result_ = false;
	time_of_last_large_drop_ms_ = now_ms;
	bitrate_before_last_large_drop_bps_ = 0;
	}

	void ProbeController::Process() {
	rtc::CritScope cs(&critsect_);

	int64_t now_ms = clock_->TimeInMilliseconds();

	if (now_ms - time_last_probing_initiated_ms_ >
	kMaxWaitingTimeForProbingResultMs) {
	mid_call_probing_waiting_for_result_ = false;

	if (state_ == State::kWaitingForProbingResult) {
	LOG(LS_INFO) << "kWaitingForProbingResult: timeout";
	state_ = State::kProbingComplete;
	min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
	}
	}

	if (state_ != State::kProbingComplete \|\| !enable_periodic_alr_probing_)
	return;

	// Probe bandwidth periodically when in ALR state.
	rtc::Optional<int64_t> alr_start_time =
	pacer_->GetApplicationLimitedRegionStartTime();
	if (alr_start_time && estimated_bitrate_bps_ > 0) {
	int64_t next_probe_time_ms =
	std::max(*alr_start_time, time_last_probing_initiated_ms_) +
	kAlrPeriodicProbingIntervalMs;
	if (now_ms >= next_probe_time_ms) {
	InitiateProbing(now_ms, {estimated_bitrate_bps_ * 2}, true);
	}
	}
	}

	void ProbeController::InitiateProbing(
	int64_t now_ms,
	std::initializer_list<int64_t> bitrates_to_probe,
	bool probe_further) {
	for (int64_t bitrate : bitrates_to_probe) {
	RTC_DCHECK_GT(bitrate, 0);
	int64_t max_probe_bitrate_bps =
	max_bitrate_bps_ > 0 ? max_bitrate_bps_ : kDefaultMaxProbingBitrateBps;
	if (bitrate > max_probe_bitrate_bps) {
	bitrate = max_probe_bitrate_bps;
	probe_further = false;
	}
	pacer_->CreateProbeCluster(rtc::dchecked_cast<int>(bitrate));
	}
	time_last_probing_initiated_ms_ = now_ms;
	if (probe_further) {
	state_ = State::kWaitingForProbingResult;
	min_bitrate_to_probe_further_bps_ =
	((bitrates_to_probe.end() - 1)) kRepeatedProbeMinPercentage / 100;
	} else {
	state_ = State::kProbingComplete;
	min_bitrate_to_probe_further_bps_ = kExponentialProbingDisabled;
	}
	}

	} // namespace webrtc