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/*
* 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 "absl/types/optional.h"
#include "modules/rtp_rtcp/source/time_util.h"
#include "system_wrappers/include/clock.h"
#include "system_wrappers/include/ntp_time.h"
#include "test/gmock.h"
#include "test/gtest.h"
namespace webrtc {
namespace {
constexpr TimeDelta kTestRtt = TimeDelta::Millis(10);
constexpr Timestamp kLocalClockInitialTime = Timestamp::Millis(123);
constexpr Timestamp kRemoteClockInitialTime = Timestamp::Millis(373);
constexpr uint32_t kTimestampOffset = 567;
constexpr int64_t kRemoteToLocalClockOffsetNtp =
ToNtpUnits(kLocalClockInitialTime - kRemoteClockInitialTime);
class RemoteNtpTimeEstimatorTest : public ::testing::Test {
protected:
void AdvanceTime(TimeDelta delta) {
local_clock_.AdvanceTime(delta);
remote_clock_.AdvanceTime(delta);
}
uint32_t GetRemoteTimestamp() {
return static_cast<uint32_t>(remote_clock_.TimeInMilliseconds()) * 90 +
kTimestampOffset;
}
void SendRtcpSr() {
uint32_t rtcp_timestamp = GetRemoteTimestamp();
NtpTime ntp = remote_clock_.CurrentNtpTime();
AdvanceTime(kTestRtt / 2);
RTC_DCHECK(estimator_.UpdateRtcpTimestamp(kTestRtt, ntp, rtcp_timestamp));
}
void SendRtcpSrInaccurately(TimeDelta ntp_error, TimeDelta networking_delay) {
uint32_t rtcp_timestamp = GetRemoteTimestamp();
int64_t ntp_error_fractions = ToNtpUnits(ntp_error);
NtpTime ntp(static_cast<uint64_t>(remote_clock_.CurrentNtpTime()) +
ntp_error_fractions);
AdvanceTime(kTestRtt / 2 + networking_delay);
RTC_DCHECK(estimator_.UpdateRtcpTimestamp(kTestRtt, ntp, rtcp_timestamp));
}
SimulatedClock local_clock_{kLocalClockInitialTime};
SimulatedClock remote_clock_{kRemoteClockInitialTime};
RemoteNtpTimeEstimator estimator_{&local_clock_};
};
TEST_F(RemoteNtpTimeEstimatorTest, FailsWithoutValidNtpTime) {
EXPECT_FALSE(
estimator_.UpdateRtcpTimestamp(kTestRtt, NtpTime(), /*rtp_timestamp=*/0));
}
TEST_F(RemoteNtpTimeEstimatorTest, Estimate) {
// Remote peer sends first RTCP SR.
SendRtcpSr();
// Remote sends a RTP packet.
AdvanceTime(TimeDelta::Millis(15));
uint32_t rtp_timestamp = GetRemoteTimestamp();
int64_t capture_ntp_time_ms = local_clock_.CurrentNtpInMilliseconds();
// Local peer needs at least 2 RTCP SR to calculate the capture time.
const int64_t kNotEnoughRtcpSr = -1;
EXPECT_EQ(kNotEnoughRtcpSr, estimator_.Estimate(rtp_timestamp));
EXPECT_EQ(estimator_.EstimateRemoteToLocalClockOffset(), absl::nullopt);
AdvanceTime(TimeDelta::Millis(800));
// Remote sends second RTCP SR.
SendRtcpSr();
// Local peer gets enough RTCP SR to calculate the capture time.
EXPECT_EQ(capture_ntp_time_ms, estimator_.Estimate(rtp_timestamp));
EXPECT_EQ(estimator_.EstimateRemoteToLocalClockOffset(),
kRemoteToLocalClockOffsetNtp);
}
TEST_F(RemoteNtpTimeEstimatorTest, AveragesErrorsOut) {
// Remote peer sends first 10 RTCP SR without errors.
for (int i = 0; i < 10; ++i) {
AdvanceTime(TimeDelta::Seconds(1));
SendRtcpSr();
}
AdvanceTime(TimeDelta::Millis(150));
uint32_t rtp_timestamp = GetRemoteTimestamp();
int64_t capture_ntp_time_ms = local_clock_.CurrentNtpInMilliseconds();
// Local peer gets enough RTCP SR to calculate the capture time.
EXPECT_EQ(capture_ntp_time_ms, estimator_.Estimate(rtp_timestamp));
EXPECT_EQ(kRemoteToLocalClockOffsetNtp,
estimator_.EstimateRemoteToLocalClockOffset());
// Remote sends corrupted RTCP SRs
AdvanceTime(TimeDelta::Seconds(1));
SendRtcpSrInaccurately(/*ntp_error=*/TimeDelta::Millis(2),
/*networking_delay=*/TimeDelta::Millis(-1));
AdvanceTime(TimeDelta::Seconds(1));
SendRtcpSrInaccurately(/*ntp_error=*/TimeDelta::Millis(-2),
/*networking_delay=*/TimeDelta::Millis(1));
// New RTP packet to estimate timestamp.
AdvanceTime(TimeDelta::Millis(150));
rtp_timestamp = GetRemoteTimestamp();
capture_ntp_time_ms = local_clock_.CurrentNtpInMilliseconds();
// Errors should be averaged out.
EXPECT_EQ(capture_ntp_time_ms, estimator_.Estimate(rtp_timestamp));
EXPECT_EQ(kRemoteToLocalClockOffsetNtp,
estimator_.EstimateRemoteToLocalClockOffset());
}
} // namespace
} // namespace webrtc
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