1 /*
2  *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef MODULES_RTP_RTCP_INCLUDE_REMOTE_NTP_TIME_ESTIMATOR_H_
12 #define MODULES_RTP_RTCP_INCLUDE_REMOTE_NTP_TIME_ESTIMATOR_H_
13 
14 #include <stdint.h>
15 
16 #include "absl/types/optional.h"
17 #include "rtc_base/constructor_magic.h"
18 #include "rtc_base/numerics/moving_median_filter.h"
19 #include "system_wrappers/include/rtp_to_ntp_estimator.h"
20 
21 namespace webrtc {
22 
23 class Clock;
24 
25 // RemoteNtpTimeEstimator can be used to estimate a given RTP timestamp's NTP
26 // time in local timebase.
27 // Note that it needs to be trained with at least 2 RTCP SR (by calling
28 // |UpdateRtcpTimestamp|) before it can be used.
29 class RemoteNtpTimeEstimator {
30  public:
31   explicit RemoteNtpTimeEstimator(Clock* clock);
32 
33   ~RemoteNtpTimeEstimator();
34 
35   // Updates the estimator with round trip time |rtt|, NTP seconds |ntp_secs|,
36   // NTP fraction |ntp_frac| and RTP timestamp |rtp_timestamp|.
37   bool UpdateRtcpTimestamp(int64_t rtt,
38                            uint32_t ntp_secs,
39                            uint32_t ntp_frac,
40                            uint32_t rtp_timestamp);
41 
42   // Estimates the NTP timestamp in local timebase from |rtp_timestamp|.
43   // Returns the NTP timestamp in ms when success. -1 if failed.
44   int64_t Estimate(uint32_t rtp_timestamp);
45 
46   // Estimates the offset, in milliseconds, between the remote clock and the
47   // local one. This is equal to local NTP clock - remote NTP clock.
48   absl::optional<int64_t> EstimateRemoteToLocalClockOffsetMs();
49 
50  private:
51   Clock* clock_;
52   MovingMedianFilter<int64_t> ntp_clocks_offset_estimator_;
53   RtpToNtpEstimator rtp_to_ntp_;
54   int64_t last_timing_log_ms_;
55   RTC_DISALLOW_COPY_AND_ASSIGN(RemoteNtpTimeEstimator);
56 };
57 
58 }  // namespace webrtc
59 
60 #endif  // MODULES_RTP_RTCP_INCLUDE_REMOTE_NTP_TIME_ESTIMATOR_H_
61