mirror of
https://github.com/mollyim/webrtc.git
synced 2025-05-14 14:20:45 +01:00
edcb25b623
Reland of https://webrtc-review.googlesource.com/c/src/+/261311 Bug: webrtc:13757 Change-Id: I34a58100b8fadfe3dbea9ffce71829b7670daad8 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/261726 Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org> Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/main@{#36838}
109 lines
3.7 KiB
C++
109 lines
3.7 KiB
C++
/*
|
|
* Copyright (c) 2014 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/rtp_rtcp/include/remote_ntp_time_estimator.h"
|
|
|
|
#include <cstdint>
|
|
|
|
#include "modules/rtp_rtcp/source/time_util.h"
|
|
#include "rtc_base/logging.h"
|
|
#include "system_wrappers/include/clock.h"
|
|
#include "system_wrappers/include/ntp_time.h"
|
|
|
|
namespace webrtc {
|
|
|
|
namespace {
|
|
|
|
constexpr int kMinimumNumberOfSamples = 2;
|
|
constexpr TimeDelta kTimingLogInterval = TimeDelta::Seconds(10);
|
|
constexpr int kClocksOffsetSmoothingWindow = 100;
|
|
|
|
// Subtracts two NtpTime values keeping maximum precision.
|
|
int64_t Subtract(NtpTime minuend, NtpTime subtrahend) {
|
|
uint64_t a = static_cast<uint64_t>(minuend);
|
|
uint64_t b = static_cast<uint64_t>(subtrahend);
|
|
return a >= b ? static_cast<int64_t>(a - b) : -static_cast<int64_t>(b - a);
|
|
}
|
|
|
|
NtpTime Add(NtpTime lhs, int64_t rhs) {
|
|
uint64_t result = static_cast<uint64_t>(lhs);
|
|
if (rhs >= 0) {
|
|
result += static_cast<uint64_t>(rhs);
|
|
} else {
|
|
result -= static_cast<uint64_t>(-rhs);
|
|
}
|
|
return NtpTime(result);
|
|
}
|
|
|
|
} // namespace
|
|
|
|
// TODO(wu): Refactor this class so that it can be shared with
|
|
// vie_sync_module.cc.
|
|
RemoteNtpTimeEstimator::RemoteNtpTimeEstimator(Clock* clock)
|
|
: clock_(clock),
|
|
ntp_clocks_offset_estimator_(kClocksOffsetSmoothingWindow) {}
|
|
|
|
bool RemoteNtpTimeEstimator::UpdateRtcpTimestamp(TimeDelta rtt,
|
|
NtpTime sender_send_time,
|
|
uint32_t rtp_timestamp) {
|
|
switch (rtp_to_ntp_.UpdateMeasurements(sender_send_time, rtp_timestamp)) {
|
|
case RtpToNtpEstimator::kInvalidMeasurement:
|
|
return false;
|
|
case RtpToNtpEstimator::kSameMeasurement:
|
|
// No new RTCP SR since last time this function was called.
|
|
return true;
|
|
case RtpToNtpEstimator::kNewMeasurement:
|
|
break;
|
|
}
|
|
|
|
// Assume connection is symmetric and thus time to deliver the packet is half
|
|
// the round trip time.
|
|
int64_t deliver_time_ntp = ToNtpUnits(rtt) / 2;
|
|
|
|
// Update extrapolator with the new arrival time.
|
|
NtpTime receiver_arrival_time = clock_->CurrentNtpTime();
|
|
int64_t remote_to_local_clocks_offset =
|
|
Subtract(receiver_arrival_time, sender_send_time) - deliver_time_ntp;
|
|
ntp_clocks_offset_estimator_.Insert(remote_to_local_clocks_offset);
|
|
return true;
|
|
}
|
|
|
|
NtpTime RemoteNtpTimeEstimator::EstimateNtp(uint32_t rtp_timestamp) {
|
|
NtpTime sender_capture = rtp_to_ntp_.Estimate(rtp_timestamp);
|
|
if (!sender_capture.Valid()) {
|
|
return sender_capture;
|
|
}
|
|
|
|
int64_t remote_to_local_clocks_offset =
|
|
ntp_clocks_offset_estimator_.GetFilteredValue();
|
|
NtpTime receiver_capture = Add(sender_capture, remote_to_local_clocks_offset);
|
|
|
|
Timestamp now = clock_->CurrentTime();
|
|
if (now - last_timing_log_ > kTimingLogInterval) {
|
|
RTC_LOG(LS_INFO) << "RTP timestamp: " << rtp_timestamp
|
|
<< " in NTP clock: " << sender_capture.ToMs()
|
|
<< " estimated time in receiver NTP clock: "
|
|
<< receiver_capture.ToMs();
|
|
last_timing_log_ = now;
|
|
}
|
|
|
|
return receiver_capture;
|
|
}
|
|
|
|
absl::optional<int64_t>
|
|
RemoteNtpTimeEstimator::EstimateRemoteToLocalClockOffset() {
|
|
if (ntp_clocks_offset_estimator_.GetNumberOfSamplesStored() <
|
|
kMinimumNumberOfSamples) {
|
|
return absl::nullopt;
|
|
}
|
|
return ntp_clocks_offset_estimator_.GetFilteredValue();
|
|
}
|
|
|
|
} // namespace webrtc
|