Revert "Use moving median filters in RemoteNtpTimeEstimator, RtpToNtpEstimator"

This reverts commit 550b666e20a13f9c22effce878a8e0078a0f7bad.

Reason for revert: breaks downstream projects.

Original change's description:
> Use moving median filters in RemoteNtpTimeEstimator, RtpToNtpEstimator
> 
> If Webrtc-ClockEstimation experiment is enabled, median filtering is
> applied to results of RtpToNtpEstimator and RemoteNtpEstimator to smooth
> out random errors introduced by incorrect RTCP SR reports and networking
> delays.
> 
> Bug: webrtc:8468
> Change-Id: Iec6d094d2809d1efeb0b9483059167d9a03880da
> Reviewed-on: https://webrtc-review.googlesource.com/22682
> Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
> Reviewed-by: Åsa Persson <asapersson@webrtc.org>
> Reviewed-by: Per Kjellander <perkj@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#20682}

TBR=ilnik@webrtc.org,asapersson@webrtc.org,perkj@webrtc.org

Change-Id: I17345d912bbaf635612c9b399d5f9166de818190
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:8468
Reviewed-on: https://webrtc-review.googlesource.com/23320
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20689}

3 files changed, 15 insertions, 85 deletions

diff --git a/system_wrappers/BUILD.gn b/system_wrappers/BUILD.gn
index ca11b891aa..fb376fe3f6 100644
--- a/system_wrappers/BUILD.gn
+++ b/system_wrappers/BUILD.gn
@@ -101,10 +101,7 @@ rtc_static_library("system_wrappers") {
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
-  deps += [
-    "../rtc_base:rtc_base_approved",
-    "../rtc_base:rtc_numerics",
-  ]
+  deps += [ "../rtc_base:rtc_base_approved" ]
 }
 
 rtc_source_set("cpu_features_api") {
diff --git a/system_wrappers/include/rtp_to_ntp_estimator.h b/system_wrappers/include/rtp_to_ntp_estimator.h
index 3e858078e3..6aad545b16 100644
--- a/system_wrappers/include/rtp_to_ntp_estimator.h
+++ b/system_wrappers/include/rtp_to_ntp_estimator.h
@@ -15,7 +15,6 @@
 
 #include "api/optional.h"
 #include "modules/include/module_common_types_public.h"
-#include "rtc_base/numerics/moving_median_filter.h"
 #include "system_wrappers/include/ntp_time.h"
 #include "typedefs.h"  // NOLINT(build/include)
 
@@ -41,23 +40,8 @@ class RtpToNtpEstimator {
 
   // Estimated parameters from RTP and NTP timestamp pairs in |measurements_|.
   struct Parameters {
-    // Implicit conversion from int because MovingMedianFilter returns 0
-    // internally if no samples are present. However, it should never happen as
-    // we don't ask smoothing_filter_ to return anything if there were no
-    // samples.
-    Parameters(const int& value) {  // NOLINT
-      RTC_NOTREACHED();
-    }
-    Parameters() : frequency_khz(0.0), offset_ms(0.0) {}
-
     double frequency_khz;
     double offset_ms;
-
-    // Needed to make it work inside MovingMedianFilter
-    bool operator<(const Parameters& other) const;
-    bool operator==(const Parameters& other) const;
-    bool operator<=(const Parameters& other) const;
-    bool operator!=(const Parameters& other) const;
   };
 
   // Updates measurements with RTP/NTP timestamp pair from a RTCP sender report.
@@ -71,8 +55,13 @@ class RtpToNtpEstimator {
   // Returns true on success, false otherwise.
   bool Estimate(int64_t rtp_timestamp, int64_t* rtp_timestamp_ms) const;
 
-  // Returns estimated rtp to ntp linear transform parameters.
-  const rtc::Optional<Parameters> params() const;
+  const rtc::Optional<Parameters> params() const {
+    rtc::Optional<Parameters> res;
+    if (params_calculated_) {
+      res.emplace(params_);
+    }
+    return res;
+  }
 
   static const int kMaxInvalidSamples = 3;
 
@@ -82,10 +71,8 @@ class RtpToNtpEstimator {
   int consecutive_invalid_samples_;
   std::list<RtcpMeasurement> measurements_;
   Parameters params_;
-  MovingMedianFilter<Parameters> smoothing_filter_;
   bool params_calculated_;
   mutable TimestampUnwrapper unwrapper_;
-  const bool is_experiment_enabled_;
 };
 }  // namespace webrtc
 
diff --git a/system_wrappers/source/rtp_to_ntp_estimator.cc b/system_wrappers/source/rtp_to_ntp_estimator.cc
index 55cdfab402..cd33f32020 100644
--- a/system_wrappers/source/rtp_to_ntp_estimator.cc
+++ b/system_wrappers/source/rtp_to_ntp_estimator.cc
@@ -13,18 +13,11 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "system_wrappers/include/clock.h"
-#include "system_wrappers/include/field_trial.h"
 
 namespace webrtc {
 namespace {
 // Number of RTCP SR reports to use to map between RTP and NTP.
 const size_t kNumRtcpReportsToUse = 2;
-// Number of parameters samples used to smooth.
-const size_t kNumSamplesToSmooth = 20;
-
-bool IsClockEstimationExperimentEnabled() {
-  return webrtc::field_trial::IsEnabled("WebRTC-ClockEstimation");
-}
 
 // Calculates the RTP timestamp frequency from two pairs of NTP/RTP timestamps.
 bool CalculateFrequency(int64_t ntp_ms1,
@@ -50,28 +43,6 @@ bool Contains(const std::list<RtpToNtpEstimator::RtcpMeasurement>& measurements,
 }
 }  // namespace
 
-bool RtpToNtpEstimator::Parameters::operator<(const Parameters& other) const {
-  if (frequency_khz < other.frequency_khz - 1e-6) {
-    return true;
-  } else if (frequency_khz > other.frequency_khz + 1e-6) {
-    return false;
-  } else {
-    return offset_ms < other.offset_ms - 1e-6;
-  }
-}
-
-bool RtpToNtpEstimator::Parameters::operator==(const Parameters& other) const {
-  return !(other < *this || *this < other);
-}
-
-bool RtpToNtpEstimator::Parameters::operator!=(const Parameters& other) const {
-  return other < *this || *this < other;
-}
-
-bool RtpToNtpEstimator::Parameters::operator<=(const Parameters& other) const {
-  return !(other < *this);
-}
-
 RtpToNtpEstimator::RtcpMeasurement::RtcpMeasurement(uint32_t ntp_secs,
                                                     uint32_t ntp_frac,
                                                     int64_t unwrapped_timestamp)
@@ -88,18 +59,13 @@ bool RtpToNtpEstimator::RtcpMeasurement::IsEqual(
 
 // Class for converting an RTP timestamp to the NTP domain.
 RtpToNtpEstimator::RtpToNtpEstimator()
-    : consecutive_invalid_samples_(0),
-      smoothing_filter_(kNumSamplesToSmooth),
-      params_calculated_(false),
-      is_experiment_enabled_(IsClockEstimationExperimentEnabled()) {}
-
+    : consecutive_invalid_samples_(0), params_calculated_(false) {}
 RtpToNtpEstimator::~RtpToNtpEstimator() {}
 
 void RtpToNtpEstimator::UpdateParameters() {
   if (measurements_.size() != kNumRtcpReportsToUse)
     return;
 
-  Parameters params;
   int64_t timestamp_new = measurements_.front().unwrapped_rtp_timestamp;
   int64_t timestamp_old = measurements_.back().unwrapped_rtp_timestamp;
 
@@ -107,16 +73,11 @@ void RtpToNtpEstimator::UpdateParameters() {
   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_.offset_ms = timestamp_new - params_.frequency_khz * ntp_ms_new;
   params_calculated_ = true;
-  if (is_experiment_enabled_) {
-    smoothing_filter_.Insert(params);
-  } else {
-    params_ = params;
-  }
 }
 
 bool RtpToNtpEstimator::UpdateMeasurements(uint32_t ntp_secs,
@@ -133,7 +94,6 @@ bool RtpToNtpEstimator::UpdateMeasurements(uint32_t ntp_secs,
     // RTCP SR report already added.
     return true;
   }
-
   if (!new_measurement.ntp_time.Valid())
     return false;
 
@@ -162,7 +122,6 @@ bool RtpToNtpEstimator::UpdateMeasurements(uint32_t ntp_secs,
     RTC_LOG(LS_WARNING) << "Multiple consecutively invalid RTCP SR reports, "
                            "clearing measurements.";
     measurements_.clear();
-    smoothing_filter_.Reset();
     params_calculated_ = false;
   }
   consecutive_invalid_samples_ = 0;
@@ -186,15 +145,12 @@ bool RtpToNtpEstimator::Estimate(int64_t rtp_timestamp,
 
   int64_t rtp_timestamp_unwrapped = unwrapper_.Unwrap(rtp_timestamp);
 
-  Parameters params =
-      is_experiment_enabled_ ? smoothing_filter_.GetFilteredValue() : params_;
-
-  // params_calculated_ should not be true unless ms params.frequency_khz has
+  // params_calculated_ should not be true unless ms params_.frequency_khz has
   // been calculated to something non zero.
-  RTC_DCHECK_NE(params.frequency_khz, 0.0);
+  RTC_DCHECK_NE(params_.frequency_khz, 0.0);
   double rtp_ms =
-      (static_cast<double>(rtp_timestamp_unwrapped) - params.offset_ms) /
-          params.frequency_khz +
+      (static_cast<double>(rtp_timestamp_unwrapped) - params_.offset_ms) /
+          params_.frequency_khz +
       0.5f;
 
   if (rtp_ms < 0)
@@ -203,14 +159,4 @@ bool RtpToNtpEstimator::Estimate(int64_t rtp_timestamp,
   *rtp_timestamp_ms = rtp_ms;
   return true;
 }
-
-const rtc::Optional<RtpToNtpEstimator::Parameters> RtpToNtpEstimator::params()
-    const {
-  rtc::Optional<Parameters> res;
-  if (params_calculated_) {
-    res.emplace(is_experiment_enabled_ ? smoothing_filter_.GetFilteredValue()
-                                       : params_);
-  }
-  return res;
-}
 }  // namespace webrtc