modules/remote_bitrate_estimator/mimd_rate_control.cc - src/webrtc - Git at Google

 /*
  *  Copyright (c) 2014 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/remote_bitrate_estimator/mimd_rate_control.h"

 #include <algorithm>
 #include <cassert>
 #include <cmath>
 #include <cstring>

 namespace webrtc {

 const uint32_t kDefaultRttMs = 200;
 const int64_t kLogIntervalMs = 1000;

 MimdRateControl::MimdRateControl(uint32_t min_bitrate_bps)
     : min_configured_bit_rate_(min_bitrate_bps),
     max_configured_bit_rate_(30000000),
     current_bit_rate_(max_configured_bit_rate_),
     max_hold_rate_(0),
     avg_max_bit_rate_(-1.0f),
     var_max_bit_rate_(0.4f),
     rate_control_state_(kRcHold),
     came_from_state_(kRcDecrease),
     rate_control_region_(kRcMaxUnknown),
     last_bit_rate_change_(-1),
     current_input_(kBwNormal, 0, 1.0),
     updated_(false),
     time_first_incoming_estimate_(-1),
     initialized_bit_rate_(false),
     avg_change_period_(1000.0f),
     last_change_ms_(-1),
     beta_(0.9f),
     rtt_(kDefaultRttMs),
     time_of_last_log_(-1)
 {
 }

 RateControlType MimdRateControl::GetControlType() const {
   return kMimdControl;
 }

 uint32_t MimdRateControl::GetMinBitrate() const {
   return min_configured_bit_rate_;
 }

 bool MimdRateControl::ValidEstimate() const {
   return initialized_bit_rate_;
 }

 int64_t MimdRateControl::GetFeedbackInterval() const {
   return kMaxFeedbackIntervalMs;
 }

 bool MimdRateControl::TimeToReduceFurther(int64_t time_now,
                                           uint32_t incoming_bitrate_bps) const {
   const int bitrate_reduction_interval = std::max(std::min(rtt_, 200u), 10u);
   if (time_now - last_bit_rate_change_ >= bitrate_reduction_interval) {
     return true;
   }
   if (ValidEstimate()) {
     const int threshold = static_cast<int>(1.05 * incoming_bitrate_bps);
     const int bitrate_difference = LatestEstimate() - incoming_bitrate_bps;
     return bitrate_difference > threshold;
   }
   return false;
 }

 uint32_t MimdRateControl::LatestEstimate() const {
   return current_bit_rate_;
 }

 uint32_t MimdRateControl::UpdateBandwidthEstimate(int64_t now_ms) {
   current_bit_rate_ = ChangeBitRate(current_bit_rate_,
                                     current_input_._incomingBitRate,
                                     current_input_._noiseVar,
                                     now_ms);
   if (now_ms - time_of_last_log_ > kLogIntervalMs) {
     time_of_last_log_ = now_ms;
   }
   return current_bit_rate_;
 }

 void MimdRateControl::SetRtt(uint32_t rtt) {
   rtt_ = rtt;
 }

 RateControlRegion MimdRateControl::Update(const RateControlInput* input,
                                           int64_t now_ms) {
   assert(input);

   // Set the initial bit rate value to what we're receiving the first half
   // second.
   if (!initialized_bit_rate_) {
     if (time_first_incoming_estimate_ < 0) {
       if (input->_incomingBitRate > 0) {
         time_first_incoming_estimate_ = now_ms;
       }
     } else if (now_ms - time_first_incoming_estimate_ > 500 &&
                input->_incomingBitRate > 0) {
       current_bit_rate_ = input->_incomingBitRate;
       initialized_bit_rate_ = true;
     }
   }

   if (updated_ && current_input_._bwState == kBwOverusing) {
     // Only update delay factor and incoming bit rate. We always want to react
     // on an over-use.
     current_input_._noiseVar = input->_noiseVar;
     current_input_._incomingBitRate = input->_incomingBitRate;
     return rate_control_region_;
   }
   updated_ = true;
   current_input_ = *input;
   return rate_control_region_;
 }

 void MimdRateControl::SetEstimate(int bitrate_bps, int64_t now_ms) {
 }

 uint32_t MimdRateControl::ChangeBitRate(uint32_t current_bit_rate,
                                         uint32_t incoming_bit_rate,
                                         double noise_var,
                                         int64_t now_ms) {
   if (!updated_) {
     return current_bit_rate_;
   }
   updated_ = false;
   UpdateChangePeriod(now_ms);
   ChangeState(current_input_, now_ms);
   // calculated here because it's used in multiple places
   const float incoming_bit_rate_kbps = incoming_bit_rate / 1000.0f;
   // Calculate the max bit rate std dev given the normalized
   // variance and the current incoming bit rate.
   const float std_max_bit_rate = sqrt(var_max_bit_rate_ * avg_max_bit_rate_);
   bool recovery = false;
   switch (rate_control_state_) {
     case kRcHold: {
       max_hold_rate_ = std::max(max_hold_rate_, incoming_bit_rate);
       break;
     }
     case kRcIncrease: {
       if (avg_max_bit_rate_ >= 0) {
         if (incoming_bit_rate_kbps > avg_max_bit_rate_ + 3 * std_max_bit_rate) {
           ChangeRegion(kRcMaxUnknown);
           avg_max_bit_rate_ = -1.0;
         } else if (incoming_bit_rate_kbps > avg_max_bit_rate_ + 2.5 *
                    std_max_bit_rate) {
           ChangeRegion(kRcAboveMax);
         }
       }
       const uint32_t response_time = static_cast<uint32_t>(avg_change_period_ +
           0.5f) + rtt_ + 300;
       double alpha = RateIncreaseFactor(now_ms, last_bit_rate_change_,
                                         response_time, noise_var);

       current_bit_rate = static_cast<uint32_t>(current_bit_rate * alpha) + 1000;
       if (max_hold_rate_ > 0 && beta_ * max_hold_rate_ > current_bit_rate) {
         current_bit_rate = static_cast<uint32_t>(beta_ * max_hold_rate_);
         avg_max_bit_rate_ = beta_ * max_hold_rate_ / 1000.0f;
         ChangeRegion(kRcNearMax);
         recovery = true;
       }
       max_hold_rate_ = 0;
       last_bit_rate_change_ = now_ms;
       break;
     }
     case kRcDecrease: {
       if (incoming_bit_rate < min_configured_bit_rate_) {
         current_bit_rate = min_configured_bit_rate_;
       } else {
         // Set bit rate to something slightly lower than max
         // to get rid of any self-induced delay.
         current_bit_rate = static_cast<uint32_t>(beta_ * incoming_bit_rate +
             0.5);
         if (current_bit_rate > current_bit_rate_) {
           // Avoid increasing the rate when over-using.
           if (rate_control_region_ != kRcMaxUnknown) {
             current_bit_rate = static_cast<uint32_t>(beta_ * avg_max_bit_rate_ *
                 1000 + 0.5f);
           }
           current_bit_rate = std::min(current_bit_rate, current_bit_rate_);
         }
         ChangeRegion(kRcNearMax);

         if (incoming_bit_rate_kbps < avg_max_bit_rate_ - 3 * std_max_bit_rate) {
           avg_max_bit_rate_ = -1.0f;
         }

         UpdateMaxBitRateEstimate(incoming_bit_rate_kbps);
       }
       // Stay on hold until the pipes are cleared.
       ChangeState(kRcHold);
       last_bit_rate_change_ = now_ms;
       break;
     }
     default:
       assert(false);
   }
   if (!recovery && (incoming_bit_rate > 100000 || current_bit_rate > 150000) &&
       current_bit_rate > 1.5 * incoming_bit_rate) {
     // Allow changing the bit rate if we are operating at very low rates
     // Don't change the bit rate if the send side is too far off
     current_bit_rate = current_bit_rate_;
     last_bit_rate_change_ = now_ms;
   }
   return current_bit_rate;
 }

 double MimdRateControl::RateIncreaseFactor(int64_t now_ms,
                                              int64_t last_ms,
                                              uint32_t reaction_time_ms,
                                              double noise_var) const {
   // alpha = 1.02 + B ./ (1 + exp(b*(tr - (c1*s2 + c2))))
   // Parameters
   const double B = 0.0407;
   const double b = 0.0025;
   const double c1 = -6700.0 / (33 * 33);
   const double c2 = 800.0;
   const double d = 0.85;

   double alpha = 1.005 + B / (1 + exp( b * (d * reaction_time_ms -
       (c1 * noise_var + c2))));

   if (alpha < 1.005) {
     alpha = 1.005;
   } else if (alpha > 1.3) {
     alpha = 1.3;
   }

   if (last_ms > -1) {
     alpha = pow(alpha, (now_ms - last_ms) / 1000.0);
   }

   if (rate_control_region_ == kRcNearMax) {
     // We're close to our previous maximum. Try to stabilize the
     // bit rate in this region, by increasing in smaller steps.
     alpha = alpha - (alpha - 1.0) / 2.0;
   } else if (rate_control_region_ == kRcMaxUnknown) {
     alpha = alpha + (alpha - 1.0) * 2.0;
   }

   return alpha;
 }

 void MimdRateControl::UpdateChangePeriod(int64_t now_ms) {
   int64_t change_period = 0;
   if (last_change_ms_ > -1) {
     change_period = now_ms - last_change_ms_;
   }
   last_change_ms_ = now_ms;
   avg_change_period_ = 0.9f * avg_change_period_ + 0.1f * change_period;
 }

 void MimdRateControl::UpdateMaxBitRateEstimate(float incoming_bit_rate_kbps) {
   const float alpha = 0.05f;
   if (avg_max_bit_rate_ == -1.0f) {
     avg_max_bit_rate_ = incoming_bit_rate_kbps;
   } else {
     avg_max_bit_rate_ = (1 - alpha) * avg_max_bit_rate_ +
         alpha * incoming_bit_rate_kbps;
   }
   // Estimate the max bit rate variance and normalize the variance
   // with the average max bit rate.
   const float norm = std::max(avg_max_bit_rate_, 1.0f);
   var_max_bit_rate_ = (1 - alpha) * var_max_bit_rate_ +
       alpha * (avg_max_bit_rate_ - incoming_bit_rate_kbps) *
           (avg_max_bit_rate_ - incoming_bit_rate_kbps) / norm;
   // 0.4 ~= 14 kbit/s at 500 kbit/s
   if (var_max_bit_rate_ < 0.4f) {
     var_max_bit_rate_ = 0.4f;
   }
   // 2.5f ~= 35 kbit/s at 500 kbit/s
   if (var_max_bit_rate_ > 2.5f) {
     var_max_bit_rate_ = 2.5f;
   }
 }

 void MimdRateControl::ChangeState(const RateControlInput& input,
                                     int64_t now_ms) {
   switch (current_input_._bwState) {
     case kBwNormal:
       if (rate_control_state_ == kRcHold) {
         last_bit_rate_change_ = now_ms;
         ChangeState(kRcIncrease);
       }
       break;
     case kBwOverusing:
       if (rate_control_state_ != kRcDecrease) {
         ChangeState(kRcDecrease);
       }
       break;
     case kBwUnderusing:
       ChangeState(kRcHold);
       break;
     default:
       assert(false);
   }
 }

 void MimdRateControl::ChangeRegion(RateControlRegion region) {
   rate_control_region_ = region;
   switch (rate_control_region_) {
     case kRcAboveMax:
     case kRcMaxUnknown:
       beta_ = 0.9f;
       break;
     case kRcNearMax:
       beta_ = 0.95f;
       break;
     default:
       assert(false);
   }
 }

 void MimdRateControl::ChangeState(RateControlState new_state) {
   came_from_state_ = rate_control_state_;
   rate_control_state_ = new_state;
 }
 }  // namespace webrtc
	/*
	* Copyright (c) 2014 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/remote_bitrate_estimator/mimd_rate_control.h"

	#include <algorithm>
	#include <cassert>
	#include <cmath>
	#include <cstring>

	namespace webrtc {

	const uint32_t kDefaultRttMs = 200;
	const int64_t kLogIntervalMs = 1000;

	MimdRateControl::MimdRateControl(uint32_t min_bitrate_bps)
	: min_configured_bit_rate_(min_bitrate_bps),
	max_configured_bit_rate_(30000000),
	current_bit_rate_(max_configured_bit_rate_),
	max_hold_rate_(0),
	avg_max_bit_rate_(-1.0f),
	var_max_bit_rate_(0.4f),
	rate_control_state_(kRcHold),
	came_from_state_(kRcDecrease),
	rate_control_region_(kRcMaxUnknown),
	last_bit_rate_change_(-1),
	current_input_(kBwNormal, 0, 1.0),
	updated_(false),
	time_first_incoming_estimate_(-1),
	initialized_bit_rate_(false),
	avg_change_period_(1000.0f),
	last_change_ms_(-1),
	beta_(0.9f),
	rtt_(kDefaultRttMs),
	time_of_last_log_(-1)
	{
	}

	RateControlType MimdRateControl::GetControlType() const {
	return kMimdControl;
	}

	uint32_t MimdRateControl::GetMinBitrate() const {
	return min_configured_bit_rate_;
	}

	bool MimdRateControl::ValidEstimate() const {
	return initialized_bit_rate_;
	}

	int64_t MimdRateControl::GetFeedbackInterval() const {
	return kMaxFeedbackIntervalMs;
	}

	bool MimdRateControl::TimeToReduceFurther(int64_t time_now,
	uint32_t incoming_bitrate_bps) const {
	const int bitrate_reduction_interval = std::max(std::min(rtt_, 200u), 10u);
	if (time_now - last_bit_rate_change_ >= bitrate_reduction_interval) {
	return true;
	}
	if (ValidEstimate()) {
	const int threshold = static_cast<int>(1.05 * incoming_bitrate_bps);
	const int bitrate_difference = LatestEstimate() - incoming_bitrate_bps;
	return bitrate_difference > threshold;
	}
	return false;
	}

	uint32_t MimdRateControl::LatestEstimate() const {
	return current_bit_rate_;
	}

	uint32_t MimdRateControl::UpdateBandwidthEstimate(int64_t now_ms) {
	current_bit_rate_ = ChangeBitRate(current_bit_rate_,
	current_input_._incomingBitRate,
	current_input_._noiseVar,
	now_ms);
	if (now_ms - time_of_last_log_ > kLogIntervalMs) {
	time_of_last_log_ = now_ms;
	}
	return current_bit_rate_;
	}

	void MimdRateControl::SetRtt(uint32_t rtt) {
	rtt_ = rtt;
	}

	RateControlRegion MimdRateControl::Update(const RateControlInput* input,
	int64_t now_ms) {
	assert(input);

	// Set the initial bit rate value to what we're receiving the first half
	// second.
	if (!initialized_bit_rate_) {
	if (time_first_incoming_estimate_ < 0) {
	if (input->_incomingBitRate > 0) {
	time_first_incoming_estimate_ = now_ms;
	}
	} else if (now_ms - time_first_incoming_estimate_ > 500 &&
	input->_incomingBitRate > 0) {
	current_bit_rate_ = input->_incomingBitRate;
	initialized_bit_rate_ = true;
	}
	}

	if (updated_ && current_input_._bwState == kBwOverusing) {
	// Only update delay factor and incoming bit rate. We always want to react
	// on an over-use.
	current_input_._noiseVar = input->_noiseVar;
	current_input_._incomingBitRate = input->_incomingBitRate;
	return rate_control_region_;
	}
	updated_ = true;
	current_input_ = *input;
	return rate_control_region_;
	}

	void MimdRateControl::SetEstimate(int bitrate_bps, int64_t now_ms) {
	}

	uint32_t MimdRateControl::ChangeBitRate(uint32_t current_bit_rate,
	uint32_t incoming_bit_rate,
	double noise_var,
	int64_t now_ms) {
	if (!updated_) {
	return current_bit_rate_;
	}
	updated_ = false;
	UpdateChangePeriod(now_ms);
	ChangeState(current_input_, now_ms);
	// calculated here because it's used in multiple places
	const float incoming_bit_rate_kbps = incoming_bit_rate / 1000.0f;
	// Calculate the max bit rate std dev given the normalized
	// variance and the current incoming bit rate.
	const float std_max_bit_rate = sqrt(var_max_bit_rate_ * avg_max_bit_rate_);
	bool recovery = false;
	switch (rate_control_state_) {
	case kRcHold: {
	max_hold_rate_ = std::max(max_hold_rate_, incoming_bit_rate);
	break;
	}
	case kRcIncrease: {
	if (avg_max_bit_rate_ >= 0) {
	if (incoming_bit_rate_kbps > avg_max_bit_rate_ + 3 * std_max_bit_rate) {
	ChangeRegion(kRcMaxUnknown);
	avg_max_bit_rate_ = -1.0;
	} else if (incoming_bit_rate_kbps > avg_max_bit_rate_ + 2.5 *
	std_max_bit_rate) {
	ChangeRegion(kRcAboveMax);
	}
	}
	const uint32_t response_time = static_cast<uint32_t>(avg_change_period_ +
	0.5f) + rtt_ + 300;
	double alpha = RateIncreaseFactor(now_ms, last_bit_rate_change_,
	response_time, noise_var);

	current_bit_rate = static_cast<uint32_t>(current_bit_rate * alpha) + 1000;
	if (max_hold_rate_ > 0 && beta_ * max_hold_rate_ > current_bit_rate) {
	current_bit_rate = static_cast<uint32_t>(beta_ * max_hold_rate_);
	avg_max_bit_rate_ = beta_ * max_hold_rate_ / 1000.0f;
	ChangeRegion(kRcNearMax);
	recovery = true;
	}
	max_hold_rate_ = 0;
	last_bit_rate_change_ = now_ms;
	break;
	}
	case kRcDecrease: {
	if (incoming_bit_rate < min_configured_bit_rate_) {
	current_bit_rate = min_configured_bit_rate_;
	} else {
	// Set bit rate to something slightly lower than max
	// to get rid of any self-induced delay.
	current_bit_rate = static_cast<uint32_t>(beta_ * incoming_bit_rate +
	0.5);
	if (current_bit_rate > current_bit_rate_) {
	// Avoid increasing the rate when over-using.
	if (rate_control_region_ != kRcMaxUnknown) {
	current_bit_rate = static_cast<uint32_t>(beta_ * avg_max_bit_rate_ *
	1000 + 0.5f);
	}
	current_bit_rate = std::min(current_bit_rate, current_bit_rate_);
	}
	ChangeRegion(kRcNearMax);

	if (incoming_bit_rate_kbps < avg_max_bit_rate_ - 3 * std_max_bit_rate) {
	avg_max_bit_rate_ = -1.0f;
	}

	UpdateMaxBitRateEstimate(incoming_bit_rate_kbps);
	}
	// Stay on hold until the pipes are cleared.
	ChangeState(kRcHold);
	last_bit_rate_change_ = now_ms;
	break;
	}
	default:
	assert(false);
	}
	if (!recovery && (incoming_bit_rate > 100000 \|\| current_bit_rate > 150000) &&
	current_bit_rate > 1.5 * incoming_bit_rate) {
	// Allow changing the bit rate if we are operating at very low rates
	// Don't change the bit rate if the send side is too far off
	current_bit_rate = current_bit_rate_;
	last_bit_rate_change_ = now_ms;
	}
	return current_bit_rate;
	}

	double MimdRateControl::RateIncreaseFactor(int64_t now_ms,
	int64_t last_ms,
	uint32_t reaction_time_ms,
	double noise_var) const {
	// alpha = 1.02 + B ./ (1 + exp(b(tr - (c1s2 + c2))))
	// Parameters
	const double B = 0.0407;
	const double b = 0.0025;
	const double c1 = -6700.0 / (33 * 33);
	const double c2 = 800.0;
	const double d = 0.85;

	double alpha = 1.005 + B / (1 + exp( b * (d * reaction_time_ms -
	(c1 * noise_var + c2))));

	if (alpha < 1.005) {
	alpha = 1.005;
	} else if (alpha > 1.3) {
	alpha = 1.3;
	}

	if (last_ms > -1) {
	alpha = pow(alpha, (now_ms - last_ms) / 1000.0);
	}

	if (rate_control_region_ == kRcNearMax) {
	// We're close to our previous maximum. Try to stabilize the
	// bit rate in this region, by increasing in smaller steps.
	alpha = alpha - (alpha - 1.0) / 2.0;
	} else if (rate_control_region_ == kRcMaxUnknown) {
	alpha = alpha + (alpha - 1.0) * 2.0;
	}

	return alpha;
	}

	void MimdRateControl::UpdateChangePeriod(int64_t now_ms) {
	int64_t change_period = 0;
	if (last_change_ms_ > -1) {
	change_period = now_ms - last_change_ms_;
	}
	last_change_ms_ = now_ms;
	avg_change_period_ = 0.9f * avg_change_period_ + 0.1f * change_period;
	}

	void MimdRateControl::UpdateMaxBitRateEstimate(float incoming_bit_rate_kbps) {
	const float alpha = 0.05f;
	if (avg_max_bit_rate_ == -1.0f) {
	avg_max_bit_rate_ = incoming_bit_rate_kbps;
	} else {
	avg_max_bit_rate_ = (1 - alpha) * avg_max_bit_rate_ +
	alpha * incoming_bit_rate_kbps;
	}
	// Estimate the max bit rate variance and normalize the variance
	// with the average max bit rate.
	const float norm = std::max(avg_max_bit_rate_, 1.0f);
	var_max_bit_rate_ = (1 - alpha) * var_max_bit_rate_ +
	alpha * (avg_max_bit_rate_ - incoming_bit_rate_kbps) *
	(avg_max_bit_rate_ - incoming_bit_rate_kbps) / norm;
	// 0.4 ~= 14 kbit/s at 500 kbit/s
	if (var_max_bit_rate_ < 0.4f) {
	var_max_bit_rate_ = 0.4f;
	}
	// 2.5f ~= 35 kbit/s at 500 kbit/s
	if (var_max_bit_rate_ > 2.5f) {
	var_max_bit_rate_ = 2.5f;
	}
	}

	void MimdRateControl::ChangeState(const RateControlInput& input,
	int64_t now_ms) {
	switch (current_input_._bwState) {
	case kBwNormal:
	if (rate_control_state_ == kRcHold) {
	last_bit_rate_change_ = now_ms;
	ChangeState(kRcIncrease);
	}
	break;
	case kBwOverusing:
	if (rate_control_state_ != kRcDecrease) {
	ChangeState(kRcDecrease);
	}
	break;
	case kBwUnderusing:
	ChangeState(kRcHold);
	break;
	default:
	assert(false);
	}
	}

	void MimdRateControl::ChangeRegion(RateControlRegion region) {
	rate_control_region_ = region;
	switch (rate_control_region_) {
	case kRcAboveMax:
	case kRcMaxUnknown:
	beta_ = 0.9f;
	break;
	case kRcNearMax:
	beta_ = 0.95f;
	break;
	default:
	assert(false);
	}
	}

	void MimdRateControl::ChangeState(RateControlState new_state) {
	came_from_state_ = rate_control_state_;
	rate_control_state_ = new_state;
	}
	} // namespace webrtc