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/*
* Copyright (c) 2020 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/congestion_controller/goog_cc/inter_arrival_delta.h"
#include <algorithm>
#include <cstddef>
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
static constexpr TimeDelta kBurstDeltaThreshold = TimeDelta::Millis(5);
static constexpr TimeDelta kMaxBurstDuration = TimeDelta::Millis(100);
constexpr TimeDelta InterArrivalDelta::kArrivalTimeOffsetThreshold;
InterArrivalDelta::InterArrivalDelta(TimeDelta send_time_group_length)
: send_time_group_length_(send_time_group_length),
current_timestamp_group_(),
prev_timestamp_group_(),
num_consecutive_reordered_packets_(0) {}
bool InterArrivalDelta::ComputeDeltas(Timestamp send_time,
Timestamp arrival_time,
Timestamp system_time,
size_t packet_size,
TimeDelta* send_time_delta,
TimeDelta* arrival_time_delta,
int* packet_size_delta) {
bool calculated_deltas = false;
if (current_timestamp_group_.IsFirstPacket()) {
// We don't have enough data to update the filter, so we store it until we
// have two frames of data to process.
current_timestamp_group_.send_time = send_time;
current_timestamp_group_.first_send_time = send_time;
current_timestamp_group_.first_arrival = arrival_time;
} else if (current_timestamp_group_.first_send_time > send_time) {
// Reordered packet.
return false;
} else if (NewTimestampGroup(arrival_time, send_time)) {
// First packet of a later send burst, the previous packets sample is ready.
if (prev_timestamp_group_.complete_time.IsFinite()) {
*send_time_delta =
current_timestamp_group_.send_time - prev_timestamp_group_.send_time;
*arrival_time_delta = current_timestamp_group_.complete_time -
prev_timestamp_group_.complete_time;
TimeDelta system_time_delta = current_timestamp_group_.last_system_time -
prev_timestamp_group_.last_system_time;
if (*arrival_time_delta - system_time_delta >=
kArrivalTimeOffsetThreshold) {
RTC_LOG(LS_WARNING)
<< "The arrival time clock offset has changed (diff = "
<< arrival_time_delta->ms() - system_time_delta.ms()
<< " ms), resetting.";
Reset();
return false;
}
if (*arrival_time_delta < TimeDelta::Zero()) {
// The group of packets has been reordered since receiving its local
// arrival timestamp.
++num_consecutive_reordered_packets_;
if (num_consecutive_reordered_packets_ >= kReorderedResetThreshold) {
RTC_LOG(LS_WARNING)
<< "Packets between send burst arrived out of order, resetting:"
<< " arrival_time_delta_ms=" << arrival_time_delta->ms()
<< ", send_time_delta_ms=" << send_time_delta->ms();
Reset();
}
return false;
} else {
num_consecutive_reordered_packets_ = 0;
}
*packet_size_delta = static_cast<int>(current_timestamp_group_.size) -
static_cast<int>(prev_timestamp_group_.size);
calculated_deltas = true;
}
prev_timestamp_group_ = current_timestamp_group_;
// The new timestamp is now the current frame.
current_timestamp_group_.first_send_time = send_time;
current_timestamp_group_.send_time = send_time;
current_timestamp_group_.first_arrival = arrival_time;
current_timestamp_group_.size = 0;
} else {
current_timestamp_group_.send_time =
std::max(current_timestamp_group_.send_time, send_time);
}
// Accumulate the frame size.
current_timestamp_group_.size += packet_size;
current_timestamp_group_.complete_time = arrival_time;
current_timestamp_group_.last_system_time = system_time;
return calculated_deltas;
}
// Assumes that `timestamp` is not reordered compared to
// `current_timestamp_group_`.
bool InterArrivalDelta::NewTimestampGroup(Timestamp arrival_time,
Timestamp send_time) const {
if (current_timestamp_group_.IsFirstPacket()) {
return false;
} else if (BelongsToBurst(arrival_time, send_time)) {
return false;
} else {
return send_time - current_timestamp_group_.first_send_time >
send_time_group_length_;
}
}
bool InterArrivalDelta::BelongsToBurst(Timestamp arrival_time,
Timestamp send_time) const {
RTC_DCHECK(current_timestamp_group_.complete_time.IsFinite());
TimeDelta arrival_time_delta =
arrival_time - current_timestamp_group_.complete_time;
TimeDelta send_time_delta = send_time - current_timestamp_group_.send_time;
if (send_time_delta.IsZero())
return true;
TimeDelta propagation_delta = arrival_time_delta - send_time_delta;
if (propagation_delta < TimeDelta::Zero() &&
arrival_time_delta <= kBurstDeltaThreshold &&
arrival_time - current_timestamp_group_.first_arrival < kMaxBurstDuration)
return true;
return false;
}
void InterArrivalDelta::Reset() {
num_consecutive_reordered_packets_ = 0;
current_timestamp_group_ = SendTimeGroup();
prev_timestamp_group_ = SendTimeGroup();
}
} // namespace webrtc