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/*
* Copyright (c) 2012 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 "modules/audio_coding/neteq/delay_manager.h"
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <algorithm>
#include <numeric>
#include <string>
#include "absl/memory/memory.h"
#include "modules/audio_coding/neteq/delay_peak_detector.h"
#include "modules/audio_coding/neteq/histogram.h"
#include "modules/audio_coding/neteq/statistics_calculator.h"
#include "modules/include/module_common_types_public.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_conversions.h"
#include "rtc_base/numerics/safe_minmax.h"
#include "system_wrappers/include/field_trial.h"
namespace {
constexpr int kLimitProbability = 1020054733; // 19/20 in Q30.
constexpr int kMinBaseMinimumDelayMs = 0;
constexpr int kMaxBaseMinimumDelayMs = 10000;
constexpr int kIatFactor = 32745; // 0.9993 in Q15.
constexpr int kMaxIat = 64; // Max inter-arrival time to register.
constexpr int kMaxReorderedPackets =
10; // Max number of consecutive reordered packets.
constexpr int kMaxHistoryPackets =
100; // Max number of packets used to calculate relative packet arrival
// delay.
constexpr int kDelayBuckets = 100;
constexpr int kBucketSizeMs = 20;
int PercentileToQuantile(double percentile) {
return static_cast<int>((1 << 30) * percentile / 100.0 + 0.5);
}
absl::optional<int> GetForcedLimitProbability() {
constexpr char kForceTargetDelayPercentileFieldTrial[] =
"WebRTC-Audio-NetEqForceTargetDelayPercentile";
const bool use_forced_target_delay_percentile =
webrtc::field_trial::IsEnabled(kForceTargetDelayPercentileFieldTrial);
if (use_forced_target_delay_percentile) {
const std::string field_trial_string = webrtc::field_trial::FindFullName(
kForceTargetDelayPercentileFieldTrial);
double percentile = -1.0;
if (sscanf(field_trial_string.c_str(), "Enabled-%lf", &percentile) == 1 &&
percentile >= 0.0 && percentile <= 100.0) {
return absl::make_optional<int>(
PercentileToQuantile(percentile)); // in Q30.
} else {
RTC_LOG(LS_WARNING) << "Invalid parameter for "
<< kForceTargetDelayPercentileFieldTrial
<< ", ignored.";
}
}
return absl::nullopt;
}
struct DelayHistogramConfig {
int quantile = 1020054733; // 0.95 in Q30.
int forget_factor = 32745; // 0.9993 in Q15.
};
absl::optional<DelayHistogramConfig> GetDelayHistogramConfig() {
constexpr char kDelayHistogramFieldTrial[] =
"WebRTC-Audio-NetEqDelayHistogram";
const bool use_new_delay_manager =
webrtc::field_trial::IsEnabled(kDelayHistogramFieldTrial);
if (use_new_delay_manager) {
const auto field_trial_string =
webrtc::field_trial::FindFullName(kDelayHistogramFieldTrial);
DelayHistogramConfig config;
double percentile = -1.0;
double forget_factor = -1.0;
if (sscanf(field_trial_string.c_str(), "Enabled-%lf-%lf", &percentile,
&forget_factor) == 2 &&
percentile >= 0.0 && percentile <= 100.0 && forget_factor >= 0.0 &&
forget_factor <= 1.0) {
config.quantile = PercentileToQuantile(percentile);
config.forget_factor = (1 << 15) * forget_factor;
}
RTC_LOG(LS_INFO) << "Delay histogram config:"
<< " quantile=" << config.quantile
<< " forget_factor=" << config.forget_factor;
return absl::make_optional(config);
}
return absl::nullopt;
}
absl::optional<int> GetDecelerationTargetLevelOffsetMs() {
constexpr char kDecelerationTargetLevelOffsetFieldTrial[] =
"WebRTC-Audio-NetEqDecelerationTargetLevelOffset";
if (!webrtc::field_trial::IsEnabled(
kDecelerationTargetLevelOffsetFieldTrial)) {
return absl::nullopt;
}
const auto field_trial_string = webrtc::field_trial::FindFullName(
kDecelerationTargetLevelOffsetFieldTrial);
int deceleration_target_level_offset_ms = -1;
sscanf(field_trial_string.c_str(), "Enabled-%d",
&deceleration_target_level_offset_ms);
if (deceleration_target_level_offset_ms >= 0) {
RTC_LOG(LS_INFO) << "NetEq deceleration_target_level_offset "
<< "in milliseconds "
<< deceleration_target_level_offset_ms;
// Convert into Q8.
return deceleration_target_level_offset_ms << 8;
}
return absl::nullopt;
}
} // namespace
namespace webrtc {
DelayManager::DelayManager(size_t max_packets_in_buffer,
int base_minimum_delay_ms,
int histogram_quantile,
HistogramMode histogram_mode,
bool enable_rtx_handling,
DelayPeakDetector* peak_detector,
const TickTimer* tick_timer,
StatisticsCalculator* statistics,
std::unique_ptr<Histogram> histogram)
: first_packet_received_(false),
max_packets_in_buffer_(max_packets_in_buffer),
histogram_(std::move(histogram)),
histogram_quantile_(histogram_quantile),
histogram_mode_(histogram_mode),
tick_timer_(tick_timer),
statistics_(statistics),
base_minimum_delay_ms_(base_minimum_delay_ms),
effective_minimum_delay_ms_(base_minimum_delay_ms),
base_target_level_(4), // In Q0 domain.
target_level_(base_target_level_ << 8), // In Q8 domain.
packet_len_ms_(0),
last_seq_no_(0),
last_timestamp_(0),
minimum_delay_ms_(0),
maximum_delay_ms_(0),
peak_detector_(*peak_detector),
last_pack_cng_or_dtmf_(1),
frame_length_change_experiment_(
field_trial::IsEnabled("WebRTC-Audio-NetEqFramelengthExperiment")),
enable_rtx_handling_(enable_rtx_handling),
deceleration_target_level_offset_ms_(
GetDecelerationTargetLevelOffsetMs()) {
assert(peak_detector); // Should never be NULL.
RTC_CHECK(histogram_);
RTC_DCHECK_GE(base_minimum_delay_ms_, 0);
RTC_DCHECK(!deceleration_target_level_offset_ms_ ||
*deceleration_target_level_offset_ms_ >= 0);
Reset();
}
std::unique_ptr<DelayManager> DelayManager::Create(
size_t max_packets_in_buffer,
int base_minimum_delay_ms,
bool enable_rtx_handling,
DelayPeakDetector* peak_detector,
const TickTimer* tick_timer,
StatisticsCalculator* statistics) {
int quantile;
std::unique_ptr<Histogram> histogram;
HistogramMode mode;
auto delay_histogram_config = GetDelayHistogramConfig();
if (delay_histogram_config) {
DelayHistogramConfig config = delay_histogram_config.value();
quantile = config.quantile;
histogram =
absl::make_unique<Histogram>(kDelayBuckets, config.forget_factor);
mode = RELATIVE_ARRIVAL_DELAY;
} else {
quantile = GetForcedLimitProbability().value_or(kLimitProbability);
histogram = absl::make_unique<Histogram>(kMaxIat + 1, kIatFactor);
mode = INTER_ARRIVAL_TIME;
}
return absl::make_unique<DelayManager>(
max_packets_in_buffer, base_minimum_delay_ms, quantile, mode,
enable_rtx_handling, peak_detector, tick_timer, statistics,
std::move(histogram));
}
DelayManager::~DelayManager() {}
int DelayManager::Update(uint16_t sequence_number,
uint32_t timestamp,
int sample_rate_hz) {
if (sample_rate_hz <= 0) {
return -1;
}
if (!first_packet_received_) {
// Prepare for next packet arrival.
packet_iat_stopwatch_ = tick_timer_->GetNewStopwatch();
last_seq_no_ = sequence_number;
last_timestamp_ = timestamp;
first_packet_received_ = true;
return 0;
}
// Try calculating packet length from current and previous timestamps.
int packet_len_ms;
if (!IsNewerTimestamp(timestamp, last_timestamp_) ||
!IsNewerSequenceNumber(sequence_number, last_seq_no_)) {
// Wrong timestamp or sequence order; use stored value.
packet_len_ms = packet_len_ms_;
} else {
// Calculate timestamps per packet and derive packet length in ms.
int64_t packet_len_samp =
static_cast<uint32_t>(timestamp - last_timestamp_) /
static_cast<uint16_t>(sequence_number - last_seq_no_);
packet_len_ms =
rtc::saturated_cast<int>(1000 * packet_len_samp / sample_rate_hz);
}
bool reordered = false;
if (packet_len_ms > 0) {
// Cannot update statistics unless |packet_len_ms| is valid.
// Inter-arrival time (IAT) in integer "packet times" (rounding down). This
// is the value added to the inter-arrival time histogram.
int iat_ms = packet_iat_stopwatch_->ElapsedMs();
int iat_packets = iat_ms / packet_len_ms;
// Check for discontinuous packet sequence and re-ordering.
if (IsNewerSequenceNumber(sequence_number, last_seq_no_ + 1)) {
// Compensate for gap in the sequence numbers. Reduce IAT with the
// expected extra time due to lost packets.
int packet_offset =
static_cast<uint16_t>(sequence_number - last_seq_no_ - 1);
iat_packets -= packet_offset;
iat_ms -= packet_offset * packet_len_ms;
} else if (!IsNewerSequenceNumber(sequence_number, last_seq_no_)) {
int packet_offset =
static_cast<uint16_t>(last_seq_no_ + 1 - sequence_number);
iat_packets += packet_offset;
iat_ms += packet_offset * packet_len_ms;
reordered = true;
}
int iat_delay = iat_ms - packet_len_ms;
int relative_delay;
if (reordered) {
relative_delay = std::max(iat_delay, 0);
} else {
UpdateDelayHistory(iat_delay);
relative_delay = CalculateRelativePacketArrivalDelay();
}
statistics_->RelativePacketArrivalDelay(relative_delay);
switch (histogram_mode_) {
case RELATIVE_ARRIVAL_DELAY: {
const int index = relative_delay / kBucketSizeMs;
if (index < histogram_->NumBuckets()) {
// Maximum delay to register is 2000 ms.
histogram_->Add(index);
}
break;
}
case INTER_ARRIVAL_TIME: {
// Saturate IAT between 0 and maximum value.
iat_packets =
std::max(std::min(iat_packets, histogram_->NumBuckets() - 1), 0);
histogram_->Add(iat_packets);
break;
}
}
// Calculate new |target_level_| based on updated statistics.
target_level_ = CalculateTargetLevel(iat_packets, reordered);
LimitTargetLevel();
} // End if (packet_len_ms > 0).
if (enable_rtx_handling_ && reordered &&
num_reordered_packets_ < kMaxReorderedPackets) {
++num_reordered_packets_;
return 0;
}
num_reordered_packets_ = 0;
// Prepare for next packet arrival.
packet_iat_stopwatch_ = tick_timer_->GetNewStopwatch();
last_seq_no_ = sequence_number;
last_timestamp_ = timestamp;
return 0;
}
void DelayManager::UpdateDelayHistory(int iat_delay) {
delay_history_.push_back(iat_delay);
if (delay_history_.size() > kMaxHistoryPackets) {
delay_history_.pop_front();
}
}
int DelayManager::CalculateRelativePacketArrivalDelay() const {
// This effectively calculates arrival delay of a packet relative to the
// packet preceding the history window. If the arrival delay ever becomes
// smaller than zero, it means the reference packet is invalid, and we
// move the reference.
int relative_delay = 0;
for (int delay : delay_history_) {
relative_delay += delay;
relative_delay = std::max(relative_delay, 0);
}
return relative_delay;
}
// Enforces upper and lower limits for |target_level_|. The upper limit is
// chosen to be minimum of i) 75% of |max_packets_in_buffer_|, to leave some
// headroom for natural fluctuations around the target, and ii) equivalent of
// |maximum_delay_ms_| in packets. Note that in practice, if no
// |maximum_delay_ms_| is specified, this does not have any impact, since the
// target level is far below the buffer capacity in all reasonable cases.
// The lower limit is equivalent of |effective_minimum_delay_ms_| in packets.
// We update |least_required_level_| while the above limits are applied.
// TODO(hlundin): Move this check to the buffer logistics class.
void DelayManager::LimitTargetLevel() {
if (packet_len_ms_ > 0 && effective_minimum_delay_ms_ > 0) {
int minimum_delay_packet_q8 =
(effective_minimum_delay_ms_ << 8) / packet_len_ms_;
target_level_ = std::max(target_level_, minimum_delay_packet_q8);
}
if (maximum_delay_ms_ > 0 && packet_len_ms_ > 0) {
int maximum_delay_packet_q8 = (maximum_delay_ms_ << 8) / packet_len_ms_;
target_level_ = std::min(target_level_, maximum_delay_packet_q8);
}
// Shift to Q8, then 75%.;
int max_buffer_packets_q8 =
static_cast<int>((3 * (max_packets_in_buffer_ << 8)) / 4);
target_level_ = std::min(target_level_, max_buffer_packets_q8);
// Sanity check, at least 1 packet (in Q8).
target_level_ = std::max(target_level_, 1 << 8);
}
int DelayManager::CalculateTargetLevel(int iat_packets, bool reordered) {
int limit_probability = histogram_quantile_;
int bucket_index = histogram_->Quantile(limit_probability);
int target_level;
switch (histogram_mode_) {
case RELATIVE_ARRIVAL_DELAY: {
target_level = 1 + bucket_index * kBucketSizeMs / packet_len_ms_;
base_target_level_ = target_level;
break;
}
case INTER_ARRIVAL_TIME: {
target_level = bucket_index;
base_target_level_ = target_level;
// Update detector for delay peaks.
bool delay_peak_found =
peak_detector_.Update(iat_packets, reordered, target_level);
if (delay_peak_found) {
target_level = std::max(target_level, peak_detector_.MaxPeakHeight());
}
break;
}
}
// Sanity check. |target_level| must be strictly positive.
target_level = std::max(target_level, 1);
// Scale to Q8 and assign to member variable.
target_level_ = target_level << 8;
return target_level_;
}
int DelayManager::SetPacketAudioLength(int length_ms) {
if (length_ms <= 0) {
RTC_LOG_F(LS_ERROR) << "length_ms = " << length_ms;
return -1;
}
if (histogram_mode_ == INTER_ARRIVAL_TIME &&
frame_length_change_experiment_ && packet_len_ms_ != length_ms &&
packet_len_ms_ > 0) {
histogram_->Scale(packet_len_ms_, length_ms);
}
packet_len_ms_ = length_ms;
peak_detector_.SetPacketAudioLength(packet_len_ms_);
packet_iat_stopwatch_ = tick_timer_->GetNewStopwatch();
last_pack_cng_or_dtmf_ = 1; // TODO(hlundin): Legacy. Remove?
return 0;
}
void DelayManager::Reset() {
packet_len_ms_ = 0; // Packet size unknown.
peak_detector_.Reset();
histogram_->Reset();
base_target_level_ = 4;
target_level_ = base_target_level_ << 8;
packet_iat_stopwatch_ = tick_timer_->GetNewStopwatch();
last_pack_cng_or_dtmf_ = 1;
}
double DelayManager::EstimatedClockDriftPpm() const {
double sum = 0.0;
// Calculate the expected value based on the probabilities in
// |histogram_|.
auto buckets = histogram_->buckets();
for (size_t i = 0; i < buckets.size(); ++i) {
sum += static_cast<double>(buckets[i]) * i;
}
// The probabilities in |histogram_| are in Q30. Divide by 1 << 30 to
// convert to Q0; subtract the nominal inter-arrival time (1) to make a zero
// clockdrift represent as 0; mulitply by 1000000 to produce parts-per-million
// (ppm).
return (sum / (1 << 30) - 1) * 1e6;
}
bool DelayManager::PeakFound() const {
return peak_detector_.peak_found();
}
void DelayManager::ResetPacketIatCount() {
packet_iat_stopwatch_ = tick_timer_->GetNewStopwatch();
}
void DelayManager::BufferLimits(int* lower_limit, int* higher_limit) const {
BufferLimits(target_level_, lower_limit, higher_limit);
}
// Note that |low_limit| and |higher_limit| are not assigned to
// |minimum_delay_ms_| and |maximum_delay_ms_| defined by the client of this
// class. They are computed from |target_level| in Q8 and used for decision
// making.
void DelayManager::BufferLimits(int target_level,
int* lower_limit,
int* higher_limit) const {
if (!lower_limit || !higher_limit) {
RTC_LOG_F(LS_ERROR) << "NULL pointers supplied as input";
assert(false);
return;
}
// |target_level| is in Q8 already.
*lower_limit = (target_level * 3) / 4;
if (deceleration_target_level_offset_ms_ && packet_len_ms_ > 0) {
*lower_limit = std::max(
*lower_limit,
target_level - *deceleration_target_level_offset_ms_ / packet_len_ms_);
}
int window_20ms = 0x7FFF; // Default large value for legacy bit-exactness.
if (packet_len_ms_ > 0) {
window_20ms = (20 << 8) / packet_len_ms_;
}
// |higher_limit| is equal to |target_level|, but should at
// least be 20 ms higher than |lower_limit|.
*higher_limit = std::max(target_level, *lower_limit + window_20ms);
}
int DelayManager::TargetLevel() const {
return target_level_;
}
void DelayManager::LastDecodedWasCngOrDtmf(bool it_was) {
if (it_was) {
last_pack_cng_or_dtmf_ = 1;
} else if (last_pack_cng_or_dtmf_ != 0) {
last_pack_cng_or_dtmf_ = -1;
}
}
void DelayManager::RegisterEmptyPacket() {
++last_seq_no_;
}
bool DelayManager::IsValidMinimumDelay(int delay_ms) const {
return 0 <= delay_ms && delay_ms <= MinimumDelayUpperBound();
}
bool DelayManager::IsValidBaseMinimumDelay(int delay_ms) const {
return kMinBaseMinimumDelayMs <= delay_ms &&
delay_ms <= kMaxBaseMinimumDelayMs;
}
bool DelayManager::SetMinimumDelay(int delay_ms) {
if (!IsValidMinimumDelay(delay_ms)) {
return false;
}
minimum_delay_ms_ = delay_ms;
UpdateEffectiveMinimumDelay();
return true;
}
bool DelayManager::SetMaximumDelay(int delay_ms) {
// If |delay_ms| is zero then it unsets the maximum delay and target level is
// unconstrained by maximum delay.
if (delay_ms != 0 &&
(delay_ms < minimum_delay_ms_ || delay_ms < packet_len_ms_)) {
// Maximum delay shouldn't be less than minimum delay or less than a packet.
return false;
}
maximum_delay_ms_ = delay_ms;
UpdateEffectiveMinimumDelay();
return true;
}
bool DelayManager::SetBaseMinimumDelay(int delay_ms) {
if (!IsValidBaseMinimumDelay(delay_ms)) {
return false;
}
base_minimum_delay_ms_ = delay_ms;
UpdateEffectiveMinimumDelay();
return true;
}
int DelayManager::GetBaseMinimumDelay() const {
return base_minimum_delay_ms_;
}
int DelayManager::base_target_level() const {
return base_target_level_;
}
int DelayManager::last_pack_cng_or_dtmf() const {
return last_pack_cng_or_dtmf_;
}
void DelayManager::set_last_pack_cng_or_dtmf(int value) {
last_pack_cng_or_dtmf_ = value;
}
void DelayManager::UpdateEffectiveMinimumDelay() {
// Clamp |base_minimum_delay_ms_| into the range which can be effectively
// used.
const int base_minimum_delay_ms =
rtc::SafeClamp(base_minimum_delay_ms_, 0, MinimumDelayUpperBound());
effective_minimum_delay_ms_ =
std::max(minimum_delay_ms_, base_minimum_delay_ms);
}
int DelayManager::MinimumDelayUpperBound() const {
// Choose the lowest possible bound discarding 0 cases which mean the value
// is not set and unconstrained.
int q75 = MaxBufferTimeQ75();
q75 = q75 > 0 ? q75 : kMaxBaseMinimumDelayMs;
const int maximum_delay_ms =
maximum_delay_ms_ > 0 ? maximum_delay_ms_ : kMaxBaseMinimumDelayMs;
return std::min(maximum_delay_ms, q75);
}
int DelayManager::MaxBufferTimeQ75() const {
const int max_buffer_time = max_packets_in_buffer_ * packet_len_ms_;
return rtc::dchecked_cast<int>(3 * max_buffer_time / 4);
}
} // namespace webrtc