Make class of static functions in rtp_to_ntp.h:

webrtc/system_wrappers/source/rtp_to_ntp_estimator.cc

 /*
  *  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.
  */
 
-#include "webrtc/system_wrappers/include/rtp_to_ntp.h"
+#include "webrtc/system_wrappers/include/rtp_to_ntp_estimator.h"
 
 #include "webrtc/base/logging.h"
 #include "webrtc/system_wrappers/include/clock.h"
 
 namespace webrtc {
 namespace {
 // Number of RTCP SR reports to use to map between RTP and NTP.
 const size_t kNumRtcpReportsToUse = 2;
 
 // Calculates the RTP timestamp frequency from two pairs of NTP/RTP timestamps.
-bool CalculateFrequency(int64_t rtcp_ntp_ms1,
+bool CalculateFrequency(int64_t ntp_ms1,
                         uint32_t rtp_timestamp1,
-                        int64_t rtcp_ntp_ms2,
+                        int64_t ntp_ms2,
                         uint32_t rtp_timestamp2,
                         double* frequency_khz) {
-  if (rtcp_ntp_ms1 <= rtcp_ntp_ms2) {
+  if (ntp_ms1 <= ntp_ms2)
     return false;
-  }
+
   *frequency_khz = static_cast<double>(rtp_timestamp1 - rtp_timestamp2) /
-      static_cast<double>(rtcp_ntp_ms1 - rtcp_ntp_ms2);
+                   static_cast<double>(ntp_ms1 - ntp_ms2);
   return true;
 }
 
 // Detects if there has been a wraparound between |old_timestamp| and
 // |new_timestamp|, and compensates by adding 2^32 if that is the case.
 bool CompensateForWrapAround(uint32_t new_timestamp,
                              uint32_t old_timestamp,
                              int64_t* compensated_timestamp) {
   int64_t wraps = CheckForWrapArounds(new_timestamp, old_timestamp);
   if (wraps < 0) {
     // Reordering, don't use this packet.
     return false;
   }
   *compensated_timestamp = new_timestamp + (wraps << 32);
   return true;
 }
-}  // namespace
 
-// Class holding RTP and NTP timestamp from a RTCP SR report.
-RtcpMeasurement::RtcpMeasurement() : ntp_time(0, 0), rtp_timestamp(0) {}
-
-RtcpMeasurement::RtcpMeasurement(uint32_t ntp_secs,
-                                 uint32_t ntp_frac,
-                                 uint32_t timestamp)
-    : ntp_time(ntp_secs, ntp_frac), rtp_timestamp(timestamp) {}
-
-bool RtcpMeasurement::IsEqual(const RtcpMeasurement& other) const {
-  // Use || since two equal timestamps will result in zero frequency and in
-  // RtpToNtpMs, |rtp_timestamp_ms| is estimated by dividing by the frequency.
-  return (ntp_time == other.ntp_time) || (rtp_timestamp == other.rtp_timestamp);
-}
-
-// Class holding list of RTP and NTP timestamp pairs.
-RtcpMeasurements::RtcpMeasurements() {}
-RtcpMeasurements::~RtcpMeasurements() {}
-
-bool RtcpMeasurements::Contains(const RtcpMeasurement& other) const {
-  for (const auto& it : list) {
-    if (it.IsEqual(other))
+bool Contains(const std::list<RtpToNtpEstimator::RtcpMeasurement>& measurements,
+              const RtpToNtpEstimator::RtcpMeasurement& other) {
+  for (const auto& measurement : measurements) {
+    if (measurement.IsEqual(other))
       return true;
   }
   return false;
 }
 
-bool RtcpMeasurements::IsValid(const RtcpMeasurement& other) const {
+bool IsValid(const std::list<RtpToNtpEstimator::RtcpMeasurement>& measurements,
+             const RtpToNtpEstimator::RtcpMeasurement& other) {
   if (!other.ntp_time.Valid())
     return false;
 
   int64_t ntp_ms_new = other.ntp_time.ToMs();
-  for (const auto& it : list) {
-    if (ntp_ms_new <= it.ntp_time.ToMs()) {
+  for (const auto& measurement : measurements) {
+    if (ntp_ms_new <= measurement.ntp_time.ToMs()) {
       // Old report.
       return false;
     }
     int64_t timestamp_new = other.rtp_timestamp;
-    if (!CompensateForWrapAround(timestamp_new, it.rtp_timestamp,
+    if (!CompensateForWrapAround(timestamp_new, measurement.rtp_timestamp,
                                  &timestamp_new)) {
       return false;
     }
-    if (timestamp_new <= it.rtp_timestamp) {
+    if (timestamp_new <= measurement.rtp_timestamp) {
       LOG(LS_WARNING) << "Newer RTCP SR report with older RTP timestamp.";
       return false;
     }
   }
   return true;
 }
+}  // namespace
 
-void RtcpMeasurements::UpdateParameters() {
-  if (list.size() != kNumRtcpReportsToUse)
+RtpToNtpEstimator::RtcpMeasurement::RtcpMeasurement(uint32_t ntp_secs,
+                                                    uint32_t ntp_frac,
+                                                    uint32_t timestamp)
+    : ntp_time(ntp_secs, ntp_frac), rtp_timestamp(timestamp) {}
+
+bool RtpToNtpEstimator::RtcpMeasurement::IsEqual(
+    const RtcpMeasurement& other) const {
+  // Use || since two equal timestamps will result in zero frequency and in
+  // RtpToNtpMs, |rtp_timestamp_ms| is estimated by dividing by the frequency.
+  return (ntp_time == other.ntp_time) || (rtp_timestamp == other.rtp_timestamp);
+}
+
+// Class for converting an RTP timestamp to the NTP domain.
+RtpToNtpEstimator::RtpToNtpEstimator() {}
+RtpToNtpEstimator::~RtpToNtpEstimator() {}
+
+void RtpToNtpEstimator::UpdateParameters() {
+  if (measurements_.size() != kNumRtcpReportsToUse)
     return;
 
-  int64_t timestamp_new = list.front().rtp_timestamp;
-  int64_t timestamp_old = list.back().rtp_timestamp;
+  int64_t timestamp_new = measurements_.front().rtp_timestamp;
+  int64_t timestamp_old = measurements_.back().rtp_timestamp;
   if (!CompensateForWrapAround(timestamp_new, timestamp_old, &timestamp_new))
     return;
 
-  int64_t ntp_ms_new = list.front().ntp_time.ToMs();
-  int64_t ntp_ms_old = list.back().ntp_time.ToMs();
+  int64_t ntp_ms_new = measurements_.front().ntp_time.ToMs();
+  int64_t ntp_ms_old = measurements_.back().ntp_time.ToMs();
 
   if (!CalculateFrequency(ntp_ms_new, timestamp_new, ntp_ms_old, timestamp_old,
-                          &params.frequency_khz)) {
+                          &params_.frequency_khz)) {
     return;
   }
-  params.offset_ms = timestamp_new - params.frequency_khz * ntp_ms_new;
-  params.calculated = true;
+  params_.offset_ms = timestamp_new - params_.frequency_khz * ntp_ms_new;
+  params_.calculated = true;
 }
 
-// Updates list holding NTP and RTP timestamp pairs.
-bool UpdateRtcpList(uint32_t ntp_secs,
-                    uint32_t ntp_frac,
-                    uint32_t rtp_timestamp,
-                    RtcpMeasurements* rtcp_measurements,
-                    bool* new_rtcp_sr) {
+bool RtpToNtpEstimator::UpdateMeasurements(uint32_t ntp_secs,
+                                           uint32_t ntp_frac,
+                                           uint32_t rtp_timestamp,
+                                           bool* new_rtcp_sr) {
   *new_rtcp_sr = false;
 
   RtcpMeasurement measurement(ntp_secs, ntp_frac, rtp_timestamp);
-  if (rtcp_measurements->Contains(measurement)) {
+  if (Contains(measurements_, measurement)) {
     // RTCP SR report already added.
     return true;
   }
-
-  if (!rtcp_measurements->IsValid(measurement)) {
+  if (!IsValid(measurements_, measurement)) {
     // Old report or invalid parameters.
     return false;
   }
 
   // Insert new RTCP SR report.
-  if (rtcp_measurements->list.size() == kNumRtcpReportsToUse)
-    rtcp_measurements->list.pop_back();
+  if (measurements_.size() == kNumRtcpReportsToUse)
+    measurements_.pop_back();
 
-  rtcp_measurements->list.push_front(measurement);
+  measurements_.push_front(measurement);
   *new_rtcp_sr = true;
 
   // List updated, calculate new parameters.
-  rtcp_measurements->UpdateParameters();
+  UpdateParameters();
   return true;
 }
 
-// Converts |rtp_timestamp| to the NTP time base using the NTP and RTP timestamp
-// pairs in |rtcp|. The converted timestamp is returned in
-// |rtp_timestamp_in_ms|. This function compensates for wrap arounds in RTP
-// timestamps and returns false if it can't do the conversion due to reordering.
-bool RtpToNtpMs(int64_t rtp_timestamp,
-                const RtcpMeasurements& rtcp,
-                int64_t* rtp_timestamp_in_ms) {
-  if (!rtcp.params.calculated || rtcp.list.empty())
+bool RtpToNtpEstimator::Estimate(int64_t rtp_timestamp,
+                                 int64_t* rtp_timestamp_ms) const {
+  if (!params_.calculated || measurements_.empty())
     return false;
 
-  uint32_t rtcp_timestamp_old = rtcp.list.back().rtp_timestamp;
+  uint32_t rtp_timestamp_old = measurements_.back().rtp_timestamp;
   int64_t rtp_timestamp_unwrapped;
-  if (!CompensateForWrapAround(rtp_timestamp, rtcp_timestamp_old,
+  if (!CompensateForWrapAround(rtp_timestamp, rtp_timestamp_old,
                                &rtp_timestamp_unwrapped)) {
     return false;
   }
 
-  double rtp_timestamp_ms =
-      (static_cast<double>(rtp_timestamp_unwrapped) - rtcp.params.offset_ms) /
-          rtcp.params.frequency_khz +
+  double rtp_ms =
+      (static_cast<double>(rtp_timestamp_unwrapped) - params_.offset_ms) /
+          params_.frequency_khz +
       0.5f;
-  if (rtp_timestamp_ms < 0) {
+
+  if (rtp_ms < 0)
     return false;
-  }
-  *rtp_timestamp_in_ms = rtp_timestamp_ms;
+
+  *rtp_timestamp_ms = rtp_ms;
   return true;
 }
 
 int CheckForWrapArounds(uint32_t new_timestamp, uint32_t old_timestamp) {
   if (new_timestamp < old_timestamp) {
     // This difference should be less than -2^31 if we have had a wrap around
     // (e.g. |new_timestamp| = 1, |rtcp_rtp_timestamp| = 2^32 - 1). Since it is
     // cast to a int32_t, it should be positive.
     if (static_cast<int32_t>(new_timestamp - old_timestamp) > 0) {
       // Forward wrap around.
       return 1;
     }
   } else if (static_cast<int32_t>(old_timestamp - new_timestamp) > 0) {
     // This difference should be less than -2^31 if we have had a backward wrap
     // around. Since it is cast to a int32_t, it should be positive.
     return -1;
   }
   return 0;
 }
 
 }  // namespace webrtc