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/*
* 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 "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_bitrate_bps_(0),
last_non_zero_bitrate_bps_(kDefaultBitrateBps),
last_fraction_loss_(0),
last_rtt_(0),
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),
allocated_without_feedback_(0),
has_packet_feedback_(false),
bitrate_allocation_strategy_(nullptr),
transmission_max_bitrate_multiplier_(
GetTransmissionMaxBitrateMultiplier()) {
sequenced_checker_.Detach();
}
BitrateAllocator::~BitrateAllocator() {
RTC_HISTOGRAM_COUNTS_100("WebRTC.Call.NumberOfPauseEvents",
num_pause_events_);
}
// 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,
uint8_t fraction_loss,
int64_t rtt,
int64_t bwe_period_ms) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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;
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);
for (auto& config : bitrate_observer_configs_) {
uint32_t allocated_bitrate = allocation[config.observer];
uint32_t protection_bitrate = config.observer->OnBitrateUpdated(
BitrateAllocationUpdate{allocated_bitrate, last_fraction_loss_,
last_rtt_, last_bwe_period_ms_});
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, config.has_packet_feedback));
}
ObserverAllocation allocation;
if (last_bitrate_bps_ > 0) {
// Calculate a new allocation and update all observers.
allocation = AllocateBitrates(last_bitrate_bps_);
for (auto& config : bitrate_observer_configs_) {
uint32_t allocated_bitrate = allocation[config.observer];
uint32_t protection_bitrate = config.observer->OnBitrateUpdated(
BitrateAllocationUpdate{allocated_bitrate, last_fraction_loss_,
last_rtt_, last_bwe_period_ms_});
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.
allocation = AllocateBitrates(last_non_zero_bitrate_bps_);
observer->OnBitrateUpdated(BitrateAllocationUpdate{
0, last_fraction_loss_, last_rtt_, last_bwe_period_ms_});
}
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;
bool has_packet_feedback = false;
uint32_t allocated_without_feedback = 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;
total_requested_max_bitrate += config.max_bitrate_bps;
if (config.allocated_bitrate_bps > 0 && config.has_packet_feedback)
has_packet_feedback = true;
// TODO(srte): Remove field trial check.
if (!config.has_packet_feedback &&
field_trial::IsEnabled("WebRTC-Audio-ABWENoTWCC"))
allocated_without_feedback += config.allocated_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_ &&
allocated_without_feedback == allocated_without_feedback_ &&
has_packet_feedback == has_packet_feedback_) {
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;
allocated_without_feedback_ = allocated_without_feedback;
has_packet_feedback_ = has_packet_feedback;
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, allocated_without_feedback,
has_packet_feedback);
}
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