Source code
Revision control
Copy as Markdown
Other Tools
/*
* 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.
*/
#ifndef MODULES_RTP_RTCP_INCLUDE_REMOTE_NTP_TIME_ESTIMATOR_H_
#define MODULES_RTP_RTCP_INCLUDE_REMOTE_NTP_TIME_ESTIMATOR_H_
#include <stdint.h>
#include <optional>
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "rtc_base/numerics/moving_percentile_filter.h"
#include "system_wrappers/include/rtp_to_ntp_estimator.h"
namespace webrtc {
class Clock;
// RemoteNtpTimeEstimator can be used to estimate a given RTP timestamp's NTP
// time in local timebase.
// Note that it needs to be trained with at least 2 RTCP SR (by calling
// `UpdateRtcpTimestamp`) before it can be used.
class RemoteNtpTimeEstimator {
public:
explicit RemoteNtpTimeEstimator(Clock* clock);
RemoteNtpTimeEstimator(const RemoteNtpTimeEstimator&) = delete;
RemoteNtpTimeEstimator& operator=(const RemoteNtpTimeEstimator&) = delete;
~RemoteNtpTimeEstimator() = default;
// Updates the estimator with round trip time `rtt` and
// new NTP time <-> RTP timestamp mapping from an RTCP sender report.
bool UpdateRtcpTimestamp(TimeDelta rtt,
NtpTime sender_send_time,
uint32_t rtp_timestamp);
// Estimates the NTP timestamp in local timebase from `rtp_timestamp`.
// Returns the NTP timestamp in ms when success. -1 if failed.
int64_t Estimate(uint32_t rtp_timestamp) {
NtpTime ntp_time = EstimateNtp(rtp_timestamp);
if (!ntp_time.Valid()) {
return -1;
}
return ntp_time.ToMs();
}
// Estimates the NTP timestamp in local timebase from `rtp_timestamp`.
// Returns invalid NtpTime (i.e. NtpTime(0)) on failure.
NtpTime EstimateNtp(uint32_t rtp_timestamp);
// Estimates the offset between the remote clock and the
// local one. This is equal to local NTP clock - remote NTP clock.
// The offset is returned in ntp time resolution, i.e. 1/2^32 sec ~= 0.2 ns.
// Returns nullopt on failure.
std::optional<int64_t> EstimateRemoteToLocalClockOffset();
private:
Clock* clock_;
// Offset is measured with the same precision as NtpTime: in 1/2^32 seconds ~=
// 0.2 ns.
MovingMedianFilter<int64_t> ntp_clocks_offset_estimator_;
RtpToNtpEstimator rtp_to_ntp_;
Timestamp last_timing_log_ = Timestamp::MinusInfinity();
};
} // namespace webrtc
#endif // MODULES_RTP_RTCP_INCLUDE_REMOTE_NTP_TIME_ESTIMATOR_H_