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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 "webrtc/call/bitrate_allocator.h"
#include <algorithm>
#include <utility>
#include "webrtc/base/checks.h"
#include "webrtc/base/logging.h"
#include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"
#include "webrtc/system_wrappers/include/clock.h"
#include "webrtc/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 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;
const int64_t kBweLogIntervalMs = 5000;
namespace {
double MediaRatio(uint32_t allocated_bitrate, uint32_t protection_bitrate) {
RTC_DCHECK_GT(allocated_bitrate, 0u);
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),
bitrate_observer_configs_(),
last_bitrate_bps_(kDefaultBitrateBps),
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) {
sequenced_checker_.Detach();
}
BitrateAllocator::~BitrateAllocator() {
RTC_HISTOGRAM_COUNTS_100("WebRTC.Call.NumberOfPauseEvents",
num_pause_events_);
}
void BitrateAllocator::OnNetworkChanged(uint32_t target_bitrate_bps,
uint8_t fraction_loss,
int64_t rtt) {
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;
// Periodically log the incoming BWE.
int64_t now = clock_->TimeInMilliseconds();
if (now > last_bwe_log_time_ + kBweLogIntervalMs) {
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(
allocated_bitrate, last_fraction_loss_, last_rtt_);
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;
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_;
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;
}
}
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_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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 (auto& config : bitrate_observer_configs_) {
uint32_t allocated_bitrate = allocation[config.observer];
uint32_t protection_bitrate = config.observer->OnBitrateUpdated(
allocated_bitrate, last_fraction_loss_, last_rtt_);
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(0, last_fraction_loss_, last_rtt_);
}
UpdateAllocationLimits();
}
void BitrateAllocator::UpdateAllocationLimits() {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
uint32_t total_requested_padding_bitrate = 0;
uint32_t total_requested_min_bitrate = 0;
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;
}
LOG(LS_INFO) << "UpdateAllocationLimits : total_requested_min_bitrate: "
<< total_requested_min_bitrate
<< "bps, total_requested_padding_bitrate: "
<< total_requested_padding_bitrate << "bps";
limit_observer_->OnAllocationLimitsChanged(total_requested_min_bitrate,
total_requested_padding_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) {
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;
}
}
BitrateAllocator::ObserverConfigs::iterator
BitrateAllocator::FindObserverConfig(const BitrateAllocatorObserver* observer) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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() {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
ObserverAllocation allocation;
for (const auto& observer_config : bitrate_observer_configs_)
allocation[observer_config.observer] = 0;
return allocation;
}
BitrateAllocator::ObserverAllocation BitrateAllocator::LowRateAllocation(
uint32_t bitrate) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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;
uint32_t required_bitrate = MinBitrateWithHysteresis(observer_config);
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 (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) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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) {
// 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.allocated_bitrate_bps == -1
? observer_config.min_bitrate_bps
: observer_config.allocated_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);
}
// 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 (observer_config.media_ratio > 0.0 && observer_config.media_ratio < 1.0)
min_bitrate += min_bitrate * (1.0 - observer_config.media_ratio);
return min_bitrate;
}
void BitrateAllocator::DistributeBitrateEvenly(uint32_t bitrate,
bool include_zero_allocations,
int max_multiplier,
ObserverAllocation* allocation) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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) {
RTC_DCHECK_CALLED_SEQUENTIALLY(&sequenced_checker_);
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