webrtc/call/bitrate_allocator.cc - src - Git at Google

 /*
  *  Copyright (c) 2015 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/call/bitrate_allocator.h"

 #include <algorithm>
 #include <utility>

 #include "webrtc/base/checks.h"
 #include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"

 namespace webrtc {

 // Allow packets to be transmitted in up to 2 times max video bitrate if the
 // bandwidth estimate allows it.
 const int kTransmissionMaxBitrateMultiplier = 2;
 const int kDefaultBitrateBps = 300000;

 // Require a bitrate increase of max(10%, 20kbps) to resume paused streams.
 const double kToggleFactor = 0.1;
 const uint32_t kMinToggleBitrateBps = 20000;

 BitrateAllocator::BitrateAllocator(LimitObserver* limit_observer)
     : limit_observer_(limit_observer),
       bitrate_observer_configs_(),
       last_bitrate_bps_(kDefaultBitrateBps),
       last_non_zero_bitrate_bps_(kDefaultBitrateBps),
       last_fraction_loss_(0),
       last_rtt_(0) {}

 void BitrateAllocator::OnNetworkChanged(uint32_t target_bitrate_bps,
                                         uint8_t fraction_loss,
                                         int64_t rtt) {
   rtc::CritScope lock(&crit_sect_);
   last_bitrate_bps_ = target_bitrate_bps;
   last_non_zero_bitrate_bps_ =
       target_bitrate_bps > 0 ? target_bitrate_bps : last_non_zero_bitrate_bps_;
   last_fraction_loss_ = fraction_loss;
   last_rtt_ = rtt;

   ObserverAllocation allocation = AllocateBitrates(target_bitrate_bps);
   for (const auto& kv : allocation) {
     kv.first->OnBitrateUpdated(kv.second, last_fraction_loss_, last_rtt_);
   }
   last_allocation_ = allocation;
 }

 void BitrateAllocator::AddObserver(BitrateAllocatorObserver* observer,
                                    uint32_t min_bitrate_bps,
                                    uint32_t max_bitrate_bps,
                                    uint32_t pad_up_bitrate_bps,
                                    bool enforce_min_bitrate) {
   rtc::CritScope lock(&crit_sect_);
   auto it = FindObserverConfig(observer);

   // Update settings if the observer already exists, create a new one otherwise.
   if (it != bitrate_observer_configs_.end()) {
     it->min_bitrate_bps = min_bitrate_bps;
     it->max_bitrate_bps = max_bitrate_bps;
     it->pad_up_bitrate_bps = pad_up_bitrate_bps;
     it->enforce_min_bitrate = enforce_min_bitrate;
   } else {
     bitrate_observer_configs_.push_back(
         ObserverConfig(observer, min_bitrate_bps, max_bitrate_bps,
                        pad_up_bitrate_bps, enforce_min_bitrate));
   }

   ObserverAllocation allocation;
   if (last_bitrate_bps_ > 0) {
     // Calculate a new allocation and update all observers.
     allocation = AllocateBitrates(last_bitrate_bps_);
     for (const auto& kv : allocation)
       kv.first->OnBitrateUpdated(kv.second, last_fraction_loss_, last_rtt_);
   } else {
     // Currently, an encoder is not allowed to produce frames.
     // But we still have to return the initial config bitrate + let the
     // observer know that it can not produce frames.
     allocation = AllocateBitrates(last_non_zero_bitrate_bps_);
     observer->OnBitrateUpdated(0, last_fraction_loss_, last_rtt_);
   }
   UpdateAllocationLimits();

   last_allocation_ = allocation;
 }

 void BitrateAllocator::UpdateAllocationLimits() {
   uint32_t total_requested_padding_bitrate = 0;
   uint32_t total_requested_min_bitrate = 0;

   {
     rtc::CritScope lock(&crit_sect_);
     for (const auto& config : bitrate_observer_configs_) {
       if (config.enforce_min_bitrate) {
         total_requested_min_bitrate += config.min_bitrate_bps;
       }
       total_requested_padding_bitrate += config.pad_up_bitrate_bps;
     }
   }

   limit_observer_->OnAllocationLimitsChanged(total_requested_min_bitrate,
                                              total_requested_padding_bitrate);
 }

 void BitrateAllocator::RemoveObserver(BitrateAllocatorObserver* observer) {
   {
     rtc::CritScope lock(&crit_sect_);
     auto it = FindObserverConfig(observer);
     if (it != bitrate_observer_configs_.end()) {
       bitrate_observer_configs_.erase(it);
     }
   }
   UpdateAllocationLimits();
 }

 int BitrateAllocator::GetStartBitrate(BitrateAllocatorObserver* observer) {
   rtc::CritScope lock(&crit_sect_);
   const auto& it = last_allocation_.find(observer);
   if (it != last_allocation_.end())
     return it->second;

   // This is a new observer that has not yet been started. Assume that if it is
   // added, all observers would split the available bitrate evenly.
   return last_non_zero_bitrate_bps_ /
          static_cast<int>((bitrate_observer_configs_.size() + 1));
 }

 BitrateAllocator::ObserverConfigList::iterator
 BitrateAllocator::FindObserverConfig(
     const BitrateAllocatorObserver* observer) {
   for (auto it = bitrate_observer_configs_.begin();
        it != bitrate_observer_configs_.end(); ++it) {
     if (it->observer == observer)
       return it;
   }
   return bitrate_observer_configs_.end();
 }

 BitrateAllocator::ObserverAllocation BitrateAllocator::AllocateBitrates(
     uint32_t bitrate) {
   if (bitrate_observer_configs_.empty())
     return ObserverAllocation();

   if (bitrate == 0)
     return ZeroRateAllocation();

   uint32_t sum_min_bitrates = 0;
   uint32_t sum_max_bitrates = 0;
   for (const auto& observer_config : bitrate_observer_configs_) {
     sum_min_bitrates += observer_config.min_bitrate_bps;
     sum_max_bitrates += observer_config.max_bitrate_bps;
   }

   // Not enough for all observers to get an allocation, allocate according to:
   // enforced min bitrate -> allocated bitrate previous round -> restart paused
   // streams.
   if (!EnoughBitrateForAllObservers(bitrate, sum_min_bitrates))
     return LowRateAllocation(bitrate);

   // All observers will get their min bitrate plus an even share of the rest.
   if (bitrate <= sum_max_bitrates)
     return NormalRateAllocation(bitrate, sum_min_bitrates);

   // All observers will get up to kTransmissionMaxBitrateMultiplier x max.
   return MaxRateAllocation(bitrate, sum_max_bitrates);
 }

 BitrateAllocator::ObserverAllocation BitrateAllocator::ZeroRateAllocation() {
   ObserverAllocation allocation;
   for (const auto& observer_config : bitrate_observer_configs_)
     allocation[observer_config.observer] = 0;
   return allocation;
 }

 BitrateAllocator::ObserverAllocation BitrateAllocator::LowRateAllocation(
     uint32_t bitrate) {
   ObserverAllocation allocation;

   // Start by allocating bitrate to observers enforcing a min bitrate, hence
   // remaining_bitrate might turn negative.
   int64_t remaining_bitrate = bitrate;
   for (const auto& observer_config : bitrate_observer_configs_) {
     int32_t allocated_bitrate = 0;
     if (observer_config.enforce_min_bitrate)
       allocated_bitrate = observer_config.min_bitrate_bps;

     allocation[observer_config.observer] = allocated_bitrate;
     remaining_bitrate -= allocated_bitrate;
   }

   // Allocate bitrate to all previously active streams.
   if (remaining_bitrate > 0) {
     for (const auto& observer_config : bitrate_observer_configs_) {
       if (observer_config.enforce_min_bitrate ||
           LastAllocatedBitrate(observer_config) == 0)
         continue;

       if (remaining_bitrate >= observer_config.min_bitrate_bps) {
         allocation[observer_config.observer] = observer_config.min_bitrate_bps;
         remaining_bitrate -= observer_config.min_bitrate_bps;
       }
     }
   }

   // Allocate bitrate to previously paused streams.
   if (remaining_bitrate > 0) {
     for (const auto& observer_config : bitrate_observer_configs_) {
       if (LastAllocatedBitrate(observer_config) != 0)
         continue;

       // Add a hysteresis to avoid toggling.
       uint32_t required_bitrate = MinBitrateWithHysteresis(observer_config);
       if (remaining_bitrate >= required_bitrate) {
         allocation[observer_config.observer] = required_bitrate;
         remaining_bitrate -= required_bitrate;
       }
     }
   }

   // Split a possible remainder evenly on all streams with an allocation.
   if (remaining_bitrate > 0)
     DistributeBitrateEvenly(remaining_bitrate, false, 1, &allocation);

   RTC_DCHECK_EQ(allocation.size(), bitrate_observer_configs_.size());
   return allocation;
 }

 BitrateAllocator::ObserverAllocation BitrateAllocator::NormalRateAllocation(
     uint32_t bitrate,
     uint32_t sum_min_bitrates) {

   ObserverAllocation allocation;
   for (const auto& observer_config : bitrate_observer_configs_)
     allocation[observer_config.observer] = observer_config.min_bitrate_bps;

   bitrate -= sum_min_bitrates;
   if (bitrate > 0)
     DistributeBitrateEvenly(bitrate, true, 1, &allocation);

   return allocation;
 }

 BitrateAllocator::ObserverAllocation BitrateAllocator::MaxRateAllocation(
     uint32_t bitrate, uint32_t sum_max_bitrates) {
   ObserverAllocation allocation;

   for (const auto& observer_config : bitrate_observer_configs_) {
     allocation[observer_config.observer] = observer_config.max_bitrate_bps;
     bitrate -= observer_config.max_bitrate_bps;
   }
   DistributeBitrateEvenly(bitrate, true, kTransmissionMaxBitrateMultiplier,
                           &allocation);
   return allocation;
 }

 uint32_t BitrateAllocator::LastAllocatedBitrate(
     const ObserverConfig& observer_config) {

   const auto& it = last_allocation_.find(observer_config.observer);
   if (it != last_allocation_.end())
     return it->second;

   // Return the configured minimum bitrate for newly added observers, to avoid
   // requiring an extra high bitrate for the observer to get an allocated
   // bitrate.
   return observer_config.min_bitrate_bps;
 }

 uint32_t BitrateAllocator::MinBitrateWithHysteresis(
     const ObserverConfig& observer_config) {
   uint32_t min_bitrate = observer_config.min_bitrate_bps;
   if (LastAllocatedBitrate(observer_config) == 0) {
     min_bitrate += std::max(static_cast<uint32_t>(kToggleFactor * min_bitrate),
                             kMinToggleBitrateBps);
   }
   return min_bitrate;
 }

 void BitrateAllocator::DistributeBitrateEvenly(uint32_t bitrate,
                                                bool include_zero_allocations,
                                                int max_multiplier,
                                                ObserverAllocation* allocation) {
   RTC_DCHECK_EQ(allocation->size(), bitrate_observer_configs_.size());

   ObserverSortingMap list_max_bitrates;
   for (const auto& observer_config : bitrate_observer_configs_) {
     if (include_zero_allocations ||
         allocation->at(observer_config.observer) != 0) {
       list_max_bitrates.insert(std::pair<uint32_t, const ObserverConfig*>(
           observer_config.max_bitrate_bps, &observer_config));
     }
   }
   auto it = list_max_bitrates.begin();
   while (it != list_max_bitrates.end()) {
     RTC_DCHECK_GT(bitrate, 0u);
     uint32_t extra_allocation =
         bitrate / static_cast<uint32_t>(list_max_bitrates.size());
     uint32_t total_allocation =
         extra_allocation + allocation->at(it->second->observer);
     bitrate -= extra_allocation;
     if (total_allocation > max_multiplier * it->first) {
       // There is more than we can fit for this observer, carry over to the
       // remaining observers.
       bitrate += total_allocation - max_multiplier * it->first;
       total_allocation = max_multiplier * it->first;
     }
     // Finally, update the allocation for this observer.
     allocation->at(it->second->observer) = total_allocation;
     it = list_max_bitrates.erase(it);
   }
 }

 bool BitrateAllocator::EnoughBitrateForAllObservers(uint32_t bitrate,
                                                     uint32_t sum_min_bitrates) {
   if (bitrate < sum_min_bitrates)
     return false;

   uint32_t extra_bitrate_per_observer = (bitrate - sum_min_bitrates) /
       static_cast<uint32_t>(bitrate_observer_configs_.size());
   for (const auto& observer_config : bitrate_observer_configs_) {
     if (observer_config.min_bitrate_bps + extra_bitrate_per_observer <
         MinBitrateWithHysteresis(observer_config))
       return false;
   }
   return true;
 }
 }  // namespace webrtc
	/*
	* Copyright (c) 2015 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/call/bitrate_allocator.h"

	#include <algorithm>
	#include <utility>

	#include "webrtc/base/checks.h"
	#include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"

	namespace webrtc {

	// Allow packets to be transmitted in up to 2 times max video bitrate if the
	// bandwidth estimate allows it.
	const int kTransmissionMaxBitrateMultiplier = 2;
	const int kDefaultBitrateBps = 300000;

	// Require a bitrate increase of max(10%, 20kbps) to resume paused streams.
	const double kToggleFactor = 0.1;
	const uint32_t kMinToggleBitrateBps = 20000;

	BitrateAllocator::BitrateAllocator(LimitObserver* limit_observer)
	: limit_observer_(limit_observer),
	bitrate_observer_configs_(),
	last_bitrate_bps_(kDefaultBitrateBps),
	last_non_zero_bitrate_bps_(kDefaultBitrateBps),
	last_fraction_loss_(0),
	last_rtt_(0) {}

	void BitrateAllocator::OnNetworkChanged(uint32_t target_bitrate_bps,
	uint8_t fraction_loss,
	int64_t rtt) {
	rtc::CritScope lock(&crit_sect_);
	last_bitrate_bps_ = target_bitrate_bps;
	last_non_zero_bitrate_bps_ =
	target_bitrate_bps > 0 ? target_bitrate_bps : last_non_zero_bitrate_bps_;
	last_fraction_loss_ = fraction_loss;
	last_rtt_ = rtt;

	ObserverAllocation allocation = AllocateBitrates(target_bitrate_bps);
	for (const auto& kv : allocation) {
	kv.first->OnBitrateUpdated(kv.second, last_fraction_loss_, last_rtt_);
	}
	last_allocation_ = allocation;
	}

	void BitrateAllocator::AddObserver(BitrateAllocatorObserver* observer,
	uint32_t min_bitrate_bps,
	uint32_t max_bitrate_bps,
	uint32_t pad_up_bitrate_bps,
	bool enforce_min_bitrate) {
	rtc::CritScope lock(&crit_sect_);
	auto it = FindObserverConfig(observer);

	// Update settings if the observer already exists, create a new one otherwise.
	if (it != bitrate_observer_configs_.end()) {
	it->min_bitrate_bps = min_bitrate_bps;
	it->max_bitrate_bps = max_bitrate_bps;
	it->pad_up_bitrate_bps = pad_up_bitrate_bps;
	it->enforce_min_bitrate = enforce_min_bitrate;
	} else {
	bitrate_observer_configs_.push_back(
	ObserverConfig(observer, min_bitrate_bps, max_bitrate_bps,
	pad_up_bitrate_bps, enforce_min_bitrate));
	}

	ObserverAllocation allocation;
	if (last_bitrate_bps_ > 0) {
	// Calculate a new allocation and update all observers.
	allocation = AllocateBitrates(last_bitrate_bps_);
	for (const auto& kv : allocation)
	kv.first->OnBitrateUpdated(kv.second, last_fraction_loss_, last_rtt_);
	} else {
	// Currently, an encoder is not allowed to produce frames.
	// But we still have to return the initial config bitrate + let the
	// observer know that it can not produce frames.
	allocation = AllocateBitrates(last_non_zero_bitrate_bps_);
	observer->OnBitrateUpdated(0, last_fraction_loss_, last_rtt_);
	}
	UpdateAllocationLimits();

	last_allocation_ = allocation;
	}

	void BitrateAllocator::UpdateAllocationLimits() {
	uint32_t total_requested_padding_bitrate = 0;
	uint32_t total_requested_min_bitrate = 0;

	{
	rtc::CritScope lock(&crit_sect_);
	for (const auto& config : bitrate_observer_configs_) {
	if (config.enforce_min_bitrate) {
	total_requested_min_bitrate += config.min_bitrate_bps;
	}
	total_requested_padding_bitrate += config.pad_up_bitrate_bps;
	}
	}

	limit_observer_->OnAllocationLimitsChanged(total_requested_min_bitrate,
	total_requested_padding_bitrate);
	}

	void BitrateAllocator::RemoveObserver(BitrateAllocatorObserver* observer) {
	{
	rtc::CritScope lock(&crit_sect_);
	auto it = FindObserverConfig(observer);
	if (it != bitrate_observer_configs_.end()) {
	bitrate_observer_configs_.erase(it);
	}
	}
	UpdateAllocationLimits();
	}

	int BitrateAllocator::GetStartBitrate(BitrateAllocatorObserver* observer) {
	rtc::CritScope lock(&crit_sect_);
	const auto& it = last_allocation_.find(observer);
	if (it != last_allocation_.end())
	return it->second;

	// This is a new observer that has not yet been started. Assume that if it is
	// added, all observers would split the available bitrate evenly.
	return last_non_zero_bitrate_bps_ /
	static_cast<int>((bitrate_observer_configs_.size() + 1));
	}

	BitrateAllocator::ObserverConfigList::iterator
	BitrateAllocator::FindObserverConfig(
	const BitrateAllocatorObserver* observer) {
	for (auto it = bitrate_observer_configs_.begin();
	it != bitrate_observer_configs_.end(); ++it) {
	if (it->observer == observer)
	return it;
	}
	return bitrate_observer_configs_.end();
	}

	BitrateAllocator::ObserverAllocation BitrateAllocator::AllocateBitrates(
	uint32_t bitrate) {
	if (bitrate_observer_configs_.empty())
	return ObserverAllocation();

	if (bitrate == 0)
	return ZeroRateAllocation();

	uint32_t sum_min_bitrates = 0;
	uint32_t sum_max_bitrates = 0;
	for (const auto& observer_config : bitrate_observer_configs_) {
	sum_min_bitrates += observer_config.min_bitrate_bps;
	sum_max_bitrates += observer_config.max_bitrate_bps;
	}

	// Not enough for all observers to get an allocation, allocate according to:
	// enforced min bitrate -> allocated bitrate previous round -> restart paused
	// streams.
	if (!EnoughBitrateForAllObservers(bitrate, sum_min_bitrates))
	return LowRateAllocation(bitrate);

	// All observers will get their min bitrate plus an even share of the rest.
	if (bitrate <= sum_max_bitrates)
	return NormalRateAllocation(bitrate, sum_min_bitrates);

	// All observers will get up to kTransmissionMaxBitrateMultiplier x max.
	return MaxRateAllocation(bitrate, sum_max_bitrates);
	}

	BitrateAllocator::ObserverAllocation BitrateAllocator::ZeroRateAllocation() {
	ObserverAllocation allocation;
	for (const auto& observer_config : bitrate_observer_configs_)
	allocation[observer_config.observer] = 0;
	return allocation;
	}

	BitrateAllocator::ObserverAllocation BitrateAllocator::LowRateAllocation(
	uint32_t bitrate) {
	ObserverAllocation allocation;

	// Start by allocating bitrate to observers enforcing a min bitrate, hence
	// remaining_bitrate might turn negative.
	int64_t remaining_bitrate = bitrate;
	for (const auto& observer_config : bitrate_observer_configs_) {
	int32_t allocated_bitrate = 0;
	if (observer_config.enforce_min_bitrate)
	allocated_bitrate = observer_config.min_bitrate_bps;

	allocation[observer_config.observer] = allocated_bitrate;
	remaining_bitrate -= allocated_bitrate;
	}

	// Allocate bitrate to all previously active streams.
	if (remaining_bitrate > 0) {
	for (const auto& observer_config : bitrate_observer_configs_) {
	if (observer_config.enforce_min_bitrate \|\|
	LastAllocatedBitrate(observer_config) == 0)
	continue;

	if (remaining_bitrate >= observer_config.min_bitrate_bps) {
	allocation[observer_config.observer] = observer_config.min_bitrate_bps;
	remaining_bitrate -= observer_config.min_bitrate_bps;
	}
	}
	}

	// Allocate bitrate to previously paused streams.
	if (remaining_bitrate > 0) {
	for (const auto& observer_config : bitrate_observer_configs_) {
	if (LastAllocatedBitrate(observer_config) != 0)
	continue;

	// Add a hysteresis to avoid toggling.
	uint32_t required_bitrate = MinBitrateWithHysteresis(observer_config);
	if (remaining_bitrate >= required_bitrate) {
	allocation[observer_config.observer] = required_bitrate;
	remaining_bitrate -= required_bitrate;
	}
	}
	}

	// Split a possible remainder evenly on all streams with an allocation.
	if (remaining_bitrate > 0)
	DistributeBitrateEvenly(remaining_bitrate, false, 1, &allocation);

	RTC_DCHECK_EQ(allocation.size(), bitrate_observer_configs_.size());
	return allocation;
	}

	BitrateAllocator::ObserverAllocation BitrateAllocator::NormalRateAllocation(
	uint32_t bitrate,
	uint32_t sum_min_bitrates) {

	ObserverAllocation allocation;
	for (const auto& observer_config : bitrate_observer_configs_)
	allocation[observer_config.observer] = observer_config.min_bitrate_bps;

	bitrate -= sum_min_bitrates;
	if (bitrate > 0)
	DistributeBitrateEvenly(bitrate, true, 1, &allocation);

	return allocation;
	}

	BitrateAllocator::ObserverAllocation BitrateAllocator::MaxRateAllocation(
	uint32_t bitrate, uint32_t sum_max_bitrates) {
	ObserverAllocation allocation;

	for (const auto& observer_config : bitrate_observer_configs_) {
	allocation[observer_config.observer] = observer_config.max_bitrate_bps;
	bitrate -= observer_config.max_bitrate_bps;
	}
	DistributeBitrateEvenly(bitrate, true, kTransmissionMaxBitrateMultiplier,
	&allocation);
	return allocation;
	}

	uint32_t BitrateAllocator::LastAllocatedBitrate(
	const ObserverConfig& observer_config) {

	const auto& it = last_allocation_.find(observer_config.observer);
	if (it != last_allocation_.end())
	return it->second;

	// Return the configured minimum bitrate for newly added observers, to avoid
	// requiring an extra high bitrate for the observer to get an allocated
	// bitrate.
	return observer_config.min_bitrate_bps;
	}

	uint32_t BitrateAllocator::MinBitrateWithHysteresis(
	const ObserverConfig& observer_config) {
	uint32_t min_bitrate = observer_config.min_bitrate_bps;
	if (LastAllocatedBitrate(observer_config) == 0) {
	min_bitrate += std::max(static_cast<uint32_t>(kToggleFactor * min_bitrate),
	kMinToggleBitrateBps);
	}
	return min_bitrate;
	}

	void BitrateAllocator::DistributeBitrateEvenly(uint32_t bitrate,
	bool include_zero_allocations,
	int max_multiplier,
	ObserverAllocation* allocation) {
	RTC_DCHECK_EQ(allocation->size(), bitrate_observer_configs_.size());

	ObserverSortingMap list_max_bitrates;
	for (const auto& observer_config : bitrate_observer_configs_) {
	if (include_zero_allocations \|\|
	allocation->at(observer_config.observer) != 0) {
	list_max_bitrates.insert(std::pair<uint32_t, const ObserverConfig*>(
	observer_config.max_bitrate_bps, &observer_config));
	}
	}
	auto it = list_max_bitrates.begin();
	while (it != list_max_bitrates.end()) {
	RTC_DCHECK_GT(bitrate, 0u);
	uint32_t extra_allocation =
	bitrate / static_cast<uint32_t>(list_max_bitrates.size());
	uint32_t total_allocation =
	extra_allocation + allocation->at(it->second->observer);
	bitrate -= extra_allocation;
	if (total_allocation > max_multiplier * it->first) {
	// There is more than we can fit for this observer, carry over to the
	// remaining observers.
	bitrate += total_allocation - max_multiplier * it->first;
	total_allocation = max_multiplier * it->first;
	}
	// Finally, update the allocation for this observer.
	allocation->at(it->second->observer) = total_allocation;
	it = list_max_bitrates.erase(it);
	}
	}

	bool BitrateAllocator::EnoughBitrateForAllObservers(uint32_t bitrate,
	uint32_t sum_min_bitrates) {
	if (bitrate < sum_min_bitrates)
	return false;

	uint32_t extra_bitrate_per_observer = (bitrate - sum_min_bitrates) /
	static_cast<uint32_t>(bitrate_observer_configs_.size());
	for (const auto& observer_config : bitrate_observer_configs_) {
	if (observer_config.min_bitrate_bps + extra_bitrate_per_observer <
	MinBitrateWithHysteresis(observer_config))
	return false;
	}
	return true;
	}
	} // namespace webrtc