| /* |
| * 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 "call/bitrate_allocator.h" |
| |
| #include <algorithm> |
| #include <cmath> |
| #include <memory> |
| #include <utility> |
| |
| #include "api/units/data_rate.h" |
| #include "api/units/time_delta.h" |
| #include "modules/bitrate_controller/include/bitrate_controller.h" |
| #include "rtc_base/checks.h" |
| #include "rtc_base/logging.h" |
| #include "system_wrappers/include/clock.h" |
| #include "system_wrappers/include/field_trial.h" |
| #include "system_wrappers/include/metrics.h" |
| |
| namespace webrtc { |
| |
| // Allow packets to be transmitted in up to 2 times max video bitrate if the |
| // bandwidth estimate allows it. |
| const uint8_t 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; |
| |
| const int64_t kBweLogIntervalMs = 5000; |
| |
| namespace { |
| |
| double MediaRatio(uint32_t allocated_bitrate, uint32_t protection_bitrate) { |
| RTC_DCHECK_GT(allocated_bitrate, 0); |
| if (protection_bitrate == 0) |
| return 1.0; |
| |
| uint32_t media_bitrate = allocated_bitrate - protection_bitrate; |
| return media_bitrate / static_cast<double>(allocated_bitrate); |
| } |
| } // namespace |
| |
| BitrateAllocator::BitrateAllocator(LimitObserver* limit_observer) |
| : limit_observer_(limit_observer), |
| last_target_bps_(0), |
| last_link_capacity_bps_(0), |
| last_non_zero_bitrate_bps_(kDefaultBitrateBps), |
| last_fraction_loss_(0), |
| last_rtt_(0), |
| last_bwe_period_ms_(1000), |
| num_pause_events_(0), |
| clock_(Clock::GetRealTimeClock()), |
| last_bwe_log_time_(0), |
| total_requested_padding_bitrate_(0), |
| total_requested_min_bitrate_(0), |
| total_requested_max_bitrate_(0), |
| bitrate_allocation_strategy_(nullptr), |
| transmission_max_bitrate_multiplier_( |
| GetTransmissionMaxBitrateMultiplier()) { |
| sequenced_checker_.Detach(); |
| } |
| |
| BitrateAllocator::~BitrateAllocator() { |
| RTC_HISTOGRAM_COUNTS_100("WebRTC.Call.NumberOfPauseEvents", |
| num_pause_events_); |
| } |
| |
| void BitrateAllocator::UpdateStartRate(uint32_t start_rate_bps) { |
| RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_); |
| last_non_zero_bitrate_bps_ = start_rate_bps; |
| } |
| |
| // static |
| uint8_t BitrateAllocator::GetTransmissionMaxBitrateMultiplier() { |
| uint64_t multiplier = strtoul(webrtc::field_trial::FindFullName( |
| "WebRTC-TransmissionMaxBitrateMultiplier") |
| .c_str(), |
| nullptr, 10); |
| if (multiplier > 0 && multiplier <= kTransmissionMaxBitrateMultiplier) { |
| RTC_LOG(LS_INFO) << "TransmissionMaxBitrateMultiplier is set to " |
| << multiplier; |
| return static_cast<uint8_t>(multiplier); |
| } |
| return kTransmissionMaxBitrateMultiplier; |
| } |
| |
| void BitrateAllocator::OnNetworkChanged(uint32_t target_bitrate_bps, |
| uint32_t link_capacity_bps, |
| uint8_t fraction_loss, |
| int64_t rtt, |
| int64_t bwe_period_ms) { |
| RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_); |
| last_target_bps_ = target_bitrate_bps; |
| last_link_capacity_bps_ = link_capacity_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; |
| last_bwe_period_ms_ = bwe_period_ms; |
| |
| // Periodically log the incoming BWE. |
| int64_t now = clock_->TimeInMilliseconds(); |
| if (now > last_bwe_log_time_ + kBweLogIntervalMs) { |
| RTC_LOG(LS_INFO) << "Current BWE " << target_bitrate_bps; |
| last_bwe_log_time_ = now; |
| } |
| |
| ObserverAllocation allocation = AllocateBitrates(target_bitrate_bps); |
| ObserverAllocation bandwidth_allocation = AllocateBitrates(link_capacity_bps); |
| |
| for (auto& config : bitrate_observer_configs_) { |
| uint32_t allocated_bitrate = allocation[config.observer]; |
| uint32_t allocated_bandwidth = bandwidth_allocation[config.observer]; |
| BitrateAllocationUpdate update; |
| update.target_bitrate = DataRate::bps(allocated_bitrate); |
| update.link_capacity = DataRate::bps(allocated_bandwidth); |
| update.packet_loss_ratio = last_fraction_loss_ / 256.0; |
| update.round_trip_time = TimeDelta::ms(last_rtt_); |
| update.bwe_period = TimeDelta::ms(last_bwe_period_ms_); |
| uint32_t protection_bitrate = config.observer->OnBitrateUpdated(update); |
| |
| if (allocated_bitrate == 0 && config.allocated_bitrate_bps > 0) { |
| if (target_bitrate_bps > 0) |
| ++num_pause_events_; |
| // The protection bitrate is an estimate based on the ratio between media |
| // and protection used before this observer was muted. |
| uint32_t predicted_protection_bps = |
| (1.0 - config.media_ratio) * config.min_bitrate_bps; |
| RTC_LOG(LS_INFO) << "Pausing observer " << config.observer |
| << " with configured min bitrate " |
| << config.min_bitrate_bps << " and current estimate of " |
| << target_bitrate_bps << " and protection bitrate " |
| << predicted_protection_bps; |
| } else if (allocated_bitrate > 0 && config.allocated_bitrate_bps == 0) { |
| if (target_bitrate_bps > 0) |
| ++num_pause_events_; |
| RTC_LOG(LS_INFO) << "Resuming observer " << config.observer |
| << ", configured min bitrate " << config.min_bitrate_bps |
| << ", current allocation " << allocated_bitrate |
| << " and protection bitrate " << protection_bitrate; |
| } |
| |
| // Only update the media ratio if the observer got an allocation. |
| if (allocated_bitrate > 0) |
| config.media_ratio = MediaRatio(allocated_bitrate, protection_bitrate); |
| config.allocated_bitrate_bps = allocated_bitrate; |
| } |
| UpdateAllocationLimits(); |
| } |
| |
| void BitrateAllocator::AddObserver(BitrateAllocatorObserver* observer, |
| MediaStreamAllocationConfig config) { |
| RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_); |
| RTC_DCHECK_GT(config.bitrate_priority, 0); |
| RTC_DCHECK(std::isnormal(config.bitrate_priority)); |
| 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 = config.min_bitrate_bps; |
| it->max_bitrate_bps = config.max_bitrate_bps; |
| it->pad_up_bitrate_bps = config.pad_up_bitrate_bps; |
| it->enforce_min_bitrate = config.enforce_min_bitrate; |
| it->bitrate_priority = config.bitrate_priority; |
| } else { |
| bitrate_observer_configs_.push_back( |
| ObserverConfig(observer, config.min_bitrate_bps, config.max_bitrate_bps, |
| config.pad_up_bitrate_bps, config.enforce_min_bitrate, |
| config.track_id, config.bitrate_priority)); |
| } |
| |
| if (last_target_bps_ > 0) { |
| // Calculate a new allocation and update all observers. |
| |
| ObserverAllocation allocation = AllocateBitrates(last_target_bps_); |
| ObserverAllocation bandwidth_allocation = |
| AllocateBitrates(last_link_capacity_bps_); |
| for (auto& config : bitrate_observer_configs_) { |
| uint32_t allocated_bitrate = allocation[config.observer]; |
| uint32_t bandwidth = bandwidth_allocation[config.observer]; |
| BitrateAllocationUpdate update; |
| update.target_bitrate = DataRate::bps(allocated_bitrate); |
| update.link_capacity = DataRate::bps(bandwidth); |
| update.packet_loss_ratio = last_fraction_loss_ / 256.0; |
| update.round_trip_time = TimeDelta::ms(last_rtt_); |
| update.bwe_period = TimeDelta::ms(last_bwe_period_ms_); |
| uint32_t protection_bitrate = config.observer->OnBitrateUpdated(update); |
| config.allocated_bitrate_bps = allocated_bitrate; |
| if (allocated_bitrate > 0) |
| config.media_ratio = MediaRatio(allocated_bitrate, protection_bitrate); |
| } |
| } 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. |
| |
| BitrateAllocationUpdate update; |
| update.target_bitrate = DataRate::Zero(); |
| update.link_capacity = DataRate::Zero(); |
| update.packet_loss_ratio = last_fraction_loss_ / 256.0; |
| update.round_trip_time = TimeDelta::ms(last_rtt_); |
| update.bwe_period = TimeDelta::ms(last_bwe_period_ms_); |
| observer->OnBitrateUpdated(update); |
| } |
| UpdateAllocationLimits(); |
| } |
| |
| void BitrateAllocator::UpdateAllocationLimits() { |
| uint32_t total_requested_padding_bitrate = 0; |
| uint32_t total_requested_min_bitrate = 0; |
| uint32_t total_requested_max_bitrate = 0; |
| for (const auto& config : bitrate_observer_configs_) { |
| uint32_t stream_padding = config.pad_up_bitrate_bps; |
| if (config.enforce_min_bitrate) { |
| total_requested_min_bitrate += config.min_bitrate_bps; |
| } else if (config.allocated_bitrate_bps == 0) { |
| stream_padding = |
| std::max(config.MinBitrateWithHysteresis(), stream_padding); |
| } |
| total_requested_padding_bitrate += stream_padding; |
| uint32_t max_bitrate_bps = config.max_bitrate_bps; |
| if (config.media_ratio < 1.0) { |
| // Account for protection overhead (eg FEC). Assumption is that overhead |
| // is never more than 100%. Don't adjust based exact value as that might |
| // trigger too frequent calls to OnAllocationLimitsChanged(). |
| max_bitrate_bps *= 2; |
| } |
| total_requested_max_bitrate += max_bitrate_bps; |
| } |
| |
| if (total_requested_padding_bitrate == total_requested_padding_bitrate_ && |
| total_requested_min_bitrate == total_requested_min_bitrate_ && |
| total_requested_max_bitrate == total_requested_max_bitrate_) { |
| return; |
| } |
| |
| total_requested_min_bitrate_ = total_requested_min_bitrate; |
| total_requested_padding_bitrate_ = total_requested_padding_bitrate; |
| total_requested_max_bitrate_ = total_requested_max_bitrate; |
| |
| RTC_LOG(LS_INFO) << "UpdateAllocationLimits : total_requested_min_bitrate: " |
| << total_requested_min_bitrate |
| << "bps, total_requested_padding_bitrate: " |
| << total_requested_padding_bitrate |
| << "bps, total_requested_max_bitrate: " |
| << total_requested_max_bitrate << "bps"; |
| limit_observer_->OnAllocationLimitsChanged(total_requested_min_bitrate, |
| total_requested_padding_bitrate, |
| total_requested_max_bitrate); |
| } |
| |
| void BitrateAllocator::RemoveObserver(BitrateAllocatorObserver* observer) { |
| RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_); |
| |
| auto it = FindObserverConfig(observer); |
| if (it != bitrate_observer_configs_.end()) { |
| bitrate_observer_configs_.erase(it); |
| } |
| |
| UpdateAllocationLimits(); |
| } |
| |
| int BitrateAllocator::GetStartBitrate( |
| BitrateAllocatorObserver* observer) const { |
| RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_); |
| const auto& it = FindObserverConfig(observer); |
| if (it == bitrate_observer_configs_.end()) { |
| // This observer hasn't been added yet, just give it its fair share. |
| return last_non_zero_bitrate_bps_ / |
| static_cast<int>((bitrate_observer_configs_.size() + 1)); |
| } else if (it->allocated_bitrate_bps == -1) { |
| // This observer hasn't received an allocation yet, so do the same. |
| return last_non_zero_bitrate_bps_ / |
| static_cast<int>(bitrate_observer_configs_.size()); |
| } else { |
| // This observer already has an allocation. |
| return it->allocated_bitrate_bps; |
| } |
| } |
| |
| void BitrateAllocator::SetBitrateAllocationStrategy( |
| std::unique_ptr<rtc::BitrateAllocationStrategy> |
| bitrate_allocation_strategy) { |
| RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_); |
| bitrate_allocation_strategy_ = std::move(bitrate_allocation_strategy); |
| } |
| |
| BitrateAllocator::ObserverConfigs::const_iterator |
| BitrateAllocator::FindObserverConfig( |
| const BitrateAllocatorObserver* observer) const { |
| 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::ObserverConfigs::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) const { |
| if (bitrate_observer_configs_.empty()) |
| return ObserverAllocation(); |
| |
| if (bitrate_allocation_strategy_ != nullptr) { |
| // Note: This intentionally causes slicing, we only copy the fields in |
| // ObserverConfig that are inherited from TrackConfig. |
| std::vector<rtc::BitrateAllocationStrategy::TrackConfig> track_configs( |
| bitrate_observer_configs_.begin(), bitrate_observer_configs_.end()); |
| |
| std::vector<uint32_t> track_allocations = |
| bitrate_allocation_strategy_->AllocateBitrates( |
| bitrate, std::move(track_configs)); |
| // The strategy should return allocation for all tracks. |
| RTC_CHECK(track_allocations.size() == bitrate_observer_configs_.size()); |
| ObserverAllocation allocation; |
| auto track_allocations_it = track_allocations.begin(); |
| for (const auto& observer_config : bitrate_observer_configs_) { |
| allocation[observer_config.observer] = *track_allocations_it++; |
| } |
| return allocation; |
| } |
| |
| 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 a share of the rest. This |
| // share is allocated to each observer based on its bitrate_priority. |
| if (bitrate <= sum_max_bitrates) |
| return NormalRateAllocation(bitrate, sum_min_bitrates); |
| |
| // All observers will get up to transmission_max_bitrate_multiplier_ x max. |
| return MaxRateAllocation(bitrate, sum_max_bitrates); |
| } |
| |
| BitrateAllocator::ObserverAllocation BitrateAllocator::ZeroRateAllocation() |
| const { |
| ObserverAllocation allocation; |
| for (const auto& observer_config : bitrate_observer_configs_) |
| allocation[observer_config.observer] = 0; |
| return allocation; |
| } |
| |
| BitrateAllocator::ObserverAllocation BitrateAllocator::LowRateAllocation( |
| uint32_t bitrate) const { |
| 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 || |
| observer_config.LastAllocatedBitrate() == 0) |
| continue; |
| |
| uint32_t required_bitrate = observer_config.MinBitrateWithHysteresis(); |
| if (remaining_bitrate >= required_bitrate) { |
| allocation[observer_config.observer] = required_bitrate; |
| remaining_bitrate -= required_bitrate; |
| } |
| } |
| } |
| |
| // Allocate bitrate to previously paused streams. |
| if (remaining_bitrate > 0) { |
| for (const auto& observer_config : bitrate_observer_configs_) { |
| if (observer_config.LastAllocatedBitrate() != 0) |
| continue; |
| |
| // Add a hysteresis to avoid toggling. |
| uint32_t required_bitrate = observer_config.MinBitrateWithHysteresis(); |
| 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; |
| } |
| |
| // Allocates the bitrate based on the bitrate priority of each observer. This |
| // bitrate priority defines the priority for bitrate to be allocated to that |
| // observer in relation to other observers. For example with two observers, if |
| // observer 1 had a bitrate_priority = 1.0, and observer 2 has a |
| // bitrate_priority = 2.0, the expected behavior is that observer 2 will be |
| // allocated twice the bitrate as observer 1 above the each observer's |
| // min_bitrate_bps values, until one of the observers hits its max_bitrate_bps. |
| BitrateAllocator::ObserverAllocation BitrateAllocator::NormalRateAllocation( |
| uint32_t bitrate, |
| uint32_t sum_min_bitrates) const { |
| ObserverAllocation allocation; |
| ObserverAllocation observers_capacities; |
| for (const auto& observer_config : bitrate_observer_configs_) { |
| allocation[observer_config.observer] = observer_config.min_bitrate_bps; |
| observers_capacities[observer_config.observer] = |
| observer_config.max_bitrate_bps - observer_config.min_bitrate_bps; |
| } |
| |
| bitrate -= sum_min_bitrates; |
| // From the remaining bitrate, allocate a proportional amount to each observer |
| // above the min bitrate already allocated. |
| if (bitrate > 0) |
| DistributeBitrateRelatively(bitrate, observers_capacities, &allocation); |
| |
| return allocation; |
| } |
| |
| BitrateAllocator::ObserverAllocation BitrateAllocator::MaxRateAllocation( |
| uint32_t bitrate, |
| uint32_t sum_max_bitrates) const { |
| 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, transmission_max_bitrate_multiplier_, |
| &allocation); |
| return allocation; |
| } |
| |
| uint32_t BitrateAllocator::ObserverConfig::LastAllocatedBitrate() const { |
| // 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 allocated_bitrate_bps == -1 ? min_bitrate_bps : allocated_bitrate_bps; |
| } |
| |
| uint32_t BitrateAllocator::ObserverConfig::MinBitrateWithHysteresis() const { |
| uint32_t min_bitrate = min_bitrate_bps; |
| if (LastAllocatedBitrate() == 0) { |
| min_bitrate += std::max(static_cast<uint32_t>(kToggleFactor * min_bitrate), |
| kMinToggleBitrateBps); |
| } |
| // Account for protection bitrate used by this observer in the previous |
| // allocation. |
| // Note: the ratio will only be updated when the stream is active, meaning a |
| // paused stream won't get any ratio updates. This might lead to waiting a bit |
| // longer than necessary if the network condition improves, but this is to |
| // avoid too much toggling. |
| if (media_ratio > 0.0 && media_ratio < 1.0) |
| min_bitrate += min_bitrate * (1.0 - media_ratio); |
| |
| return min_bitrate; |
| } |
| |
| void BitrateAllocator::DistributeBitrateEvenly( |
| uint32_t bitrate, |
| bool include_zero_allocations, |
| int max_multiplier, |
| ObserverAllocation* allocation) const { |
| 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, 0); |
| 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) const { |
| 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 < |
| observer_config.MinBitrateWithHysteresis()) { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| void BitrateAllocator::DistributeBitrateRelatively( |
| uint32_t remaining_bitrate, |
| const ObserverAllocation& observers_capacities, |
| ObserverAllocation* allocation) const { |
| RTC_DCHECK_EQ(allocation->size(), bitrate_observer_configs_.size()); |
| RTC_DCHECK_EQ(observers_capacities.size(), bitrate_observer_configs_.size()); |
| |
| struct PriorityRateObserverConfig { |
| PriorityRateObserverConfig(BitrateAllocatorObserver* allocation_key, |
| uint32_t capacity_bps, |
| double bitrate_priority) |
| : allocation_key(allocation_key), |
| capacity_bps(capacity_bps), |
| bitrate_priority(bitrate_priority) {} |
| |
| BitrateAllocatorObserver* allocation_key; |
| // The amount of bitrate bps that can be allocated to this observer. |
| uint32_t capacity_bps; |
| double bitrate_priority; |
| |
| // We want to sort by which observers will be allocated their full capacity |
| // first. By dividing each observer's capacity by its bitrate priority we |
| // are "normalizing" the capacity of an observer by the rate it will be |
| // filled. This is because the amount allocated is based upon bitrate |
| // priority. We allocate twice as much bitrate to an observer with twice the |
| // bitrate priority of another. |
| bool operator<(const PriorityRateObserverConfig& other) const { |
| return capacity_bps / bitrate_priority < |
| other.capacity_bps / other.bitrate_priority; |
| } |
| }; |
| |
| double bitrate_priority_sum = 0; |
| std::vector<PriorityRateObserverConfig> priority_rate_observers; |
| for (const auto& observer_config : bitrate_observer_configs_) { |
| uint32_t capacity_bps = observers_capacities.at(observer_config.observer); |
| priority_rate_observers.emplace_back(observer_config.observer, capacity_bps, |
| observer_config.bitrate_priority); |
| bitrate_priority_sum += observer_config.bitrate_priority; |
| } |
| |
| // Iterate in the order observers can be allocated their full capacity. |
| std::sort(priority_rate_observers.begin(), priority_rate_observers.end()); |
| size_t i; |
| for (i = 0; i < priority_rate_observers.size(); ++i) { |
| const auto& priority_rate_observer = priority_rate_observers[i]; |
| // We allocate the full capacity to an observer only if its relative |
| // portion from the remaining bitrate is sufficient to allocate its full |
| // capacity. This means we aren't greedily allocating the full capacity, but |
| // that it is only done when there is also enough bitrate to allocate the |
| // proportional amounts to all other observers. |
| double observer_share = |
| priority_rate_observer.bitrate_priority / bitrate_priority_sum; |
| double allocation_bps = observer_share * remaining_bitrate; |
| bool enough_bitrate = allocation_bps >= priority_rate_observer.capacity_bps; |
| if (!enough_bitrate) |
| break; |
| allocation->at(priority_rate_observer.allocation_key) += |
| priority_rate_observer.capacity_bps; |
| remaining_bitrate -= priority_rate_observer.capacity_bps; |
| bitrate_priority_sum -= priority_rate_observer.bitrate_priority; |
| } |
| |
| // From the remaining bitrate, allocate the proportional amounts to the |
| // observers that aren't allocated their max capacity. |
| for (; i < priority_rate_observers.size(); ++i) { |
| const auto& priority_rate_observer = priority_rate_observers[i]; |
| double fraction_allocated = |
| priority_rate_observer.bitrate_priority / bitrate_priority_sum; |
| allocation->at(priority_rate_observer.allocation_key) += |
| fraction_allocated * remaining_bitrate; |
| } |
| } |
| |
| } // namespace webrtc |
