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/*
* Copyright (c) 2018 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/receive_time_calculator.h"
#include "rtc_base/logging.h"
#include "rtc_base/ptr_util.h"
#include "system_wrappers/include/field_trial.h"
namespace webrtc {
namespace {
using ::webrtc::field_trial::FindFullName;
using ::webrtc::field_trial::IsEnabled;
const char kBweReceiveTimeCorrection[] = "WebRTC-BweReceiveTimeCorrection";
} // namespace
ReceiveTimeCalculator::ReceiveTimeCalculator(int64_t min_delta_ms,
int64_t max_delta_diff_ms)
: min_delta_us_(min_delta_ms * 1000),
max_delta_diff_us_(max_delta_diff_ms * 1000) {}
std::unique_ptr<ReceiveTimeCalculator>
ReceiveTimeCalculator::CreateFromFieldTrial() {
if (!IsEnabled(kBweReceiveTimeCorrection))
return nullptr;
int min, max;
if (sscanf(FindFullName(kBweReceiveTimeCorrection).c_str(), "Enabled,%d,%d",
&min, &max) != 2) {
RTC_LOG(LS_WARNING) << "Invalid number of parameters provided.";
return nullptr;
}
return rtc::MakeUnique<ReceiveTimeCalculator>(min, max);
}
int64_t ReceiveTimeCalculator::ReconcileReceiveTimes(int64_t packet_time_us_,
int64_t safe_time_us_) {
if (!receive_time_offset_us_) {
receive_time_offset_us_ = safe_time_us_ - packet_time_us_;
} else {
int64_t safe_delta_us = safe_time_us_ - last_safe_time_us_;
int64_t packet_delta_us_ = packet_time_us_ - last_packet_time_us_;
int64_t delta_diff = packet_delta_us_ - safe_delta_us;
// Packet time should not decrease significantly, a large decrease indicates
// a reset of the packet time clock and we should reset the offest
// parameter. The safe reference time can increase in large jumps if the
// thread measuring it is backgrounded for longer periods. But if the packet
// time increases significantly more than the safe time, it indicates a
// clock reset and we should reset the offset.
if (packet_delta_us_ < min_delta_us_ || delta_diff > max_delta_diff_us_) {
RTC_LOG(LS_WARNING) << "Received a clock jump of " << delta_diff
<< " resetting offset";
receive_time_offset_us_ = safe_time_us_ - packet_time_us_;
}
}
last_packet_time_us_ = packet_time_us_;
last_safe_time_us_ = safe_time_us_;
return packet_time_us_ + *receive_time_offset_us_;
}
} // namespace webrtc
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