1 files changed, 74 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/rtp_rtcp/include/remote_ntp_time_estimator.h b/third_party/libwebrtc/modules/rtp_rtcp/include/remote_ntp_time_estimator.h
new file mode 100644
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+++ b/third_party/libwebrtc/modules/rtp_rtcp/include/remote_ntp_time_estimator.h
@@ -0,0 +1,74 @@
+/*
+ *  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 "absl/types/optional.h"
+#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.
+  absl::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_