Make class of static functions in rtp_to_ntp.h:

webrtc/system_wrappers/include/rtp_to_ntp_estimator.h

+/*
+ *  Copyright (c) 2012 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 WEBRTC_SYSTEM_WRAPPERS_INCLUDE_RTP_TO_NTP_ESTIMATOR_H_
+#define WEBRTC_SYSTEM_WRAPPERS_INCLUDE_RTP_TO_NTP_ESTIMATOR_H_
+
+#include <list>
+
+#include "webrtc/system_wrappers/include/ntp_time.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+// Class for converting an RTP timestamp to the NTP domain in milliseconds.
+// The class needs to be trained with (at least 2) RTP/NTP timestamp pairs from
+// RTCP sender reports before the convertion can be done.
+class RtpToNtpEstimator {
+ public:
+  RtpToNtpEstimator();
+  ~RtpToNtpEstimator();
+
+  // Updates measurements with RTP/NTP timestamp pair from a RTCP sender report.
+  // |new_rtcp_sr| is set to true if a new report is added.
+  bool UpdateMeasurements(uint32_t ntp_secs,
+                          uint32_t ntp_frac,
+                          uint32_t rtp_timestamp,
+                          bool* new_rtcp_sr);
+
+  // Converts an RTP timestamp to the NTP domain in milliseconds.
+  // Returns true on success, false otherwise.
+  bool Estimate(int64_t rtp_timestamp, int64_t* rtp_timestamp_ms) const;
+
+  // Estimated parameters from RTP and NTP timestamp pairs in |measurements_|.
+  struct Parameters {
+    double frequency_khz = 0.0;
+    double offset_ms = 0.0;
+    bool calculated = false;
+  };
+
+  // RTP and NTP timestamp pair from a RTCP SR report.
+  struct RtcpMeasurement {
+    RtcpMeasurement(uint32_t ntp_secs, uint32_t ntp_frac, uint32_t timestamp);
+    bool IsEqual(const RtcpMeasurement& other) const;
+
+    NtpTime ntp_time;
+    uint32_t rtp_timestamp;
+  };
+

[stefan-webrtc, 2016/12/19 12:36:07]

Move these structs to the top of the class.

[åsapersson, 2016/12/19 15:06:47]

Done.

+  const Parameters& params() const { return params_; }
+
+  // Only for testing.
+  const std::list<RtcpMeasurement>& measurements() const {

[stefan-webrtc, 2016/12/19 12:36:07]

I'd prefer not to expose this. Can we write the tests so that they monitor the
output of Estimate() instead of measurements()?

If it's a lot of work it may not be worth it...

[åsapersson, 2016/12/19 15:06:47]

Done.

+    return measurements_;
+  }
+
+ private:
+  void UpdateParameters();
+
+  std::list<RtcpMeasurement> measurements_;
+  Parameters params_;
+};
+
+// Returns:
+//  1: forward wrap around.
+//  0: no wrap around.
+// -1: backwards wrap around (i.e. reordering).
+int CheckForWrapArounds(uint32_t new_timestamp, uint32_t old_timestamp);
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_SYSTEM_WRAPPERS_INCLUDE_RTP_TO_NTP_ESTIMATOR_H_