Reland "Move smoothing filter to common audio".

webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.cc

Index: webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.cc
diff --git a/webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.cc b/webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.cc
deleted file mode 100644
index 8a8106918a9366310df7a434c4e28a383fcf8c23..0000000000000000000000000000000000000000
--- a/webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.cc
+++ /dev/null
@@ -1,62 +0,0 @@
-/*
- *  Copyright (c) 2016 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 <cmath>
-
-#include "webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.h"
-
-namespace webrtc {
-
-SmoothingFilterImpl::SmoothingFilterImpl(int time_constant_ms,
-                                         const Clock* clock)
-    : time_constant_ms_(time_constant_ms),
-      clock_(clock),
-      first_sample_received_(false),
-      initialized_(false),
-      first_sample_time_ms_(0),
-      last_sample_time_ms_(0),
-      filter_(0.0) {}
-
-void SmoothingFilterImpl::AddSample(float sample) {
-  if (!first_sample_received_) {
-    last_sample_time_ms_ = first_sample_time_ms_ = clock_->TimeInMilliseconds();
-    first_sample_received_ = true;
-    RTC_DCHECK_EQ(rtc::ExpFilter::kValueUndefined, filter_.filtered());
-
-    // Since this is first sample, any value for argument 1 should work.
-    filter_.Apply(0.0f, sample);
-    return;
-  }
-
-  int64_t now_ms = clock_->TimeInMilliseconds();
-  if (!initialized_) {
-    float duration = now_ms - first_sample_time_ms_;
-    if (duration < static_cast<int64_t>(time_constant_ms_)) {
-      filter_.UpdateBase(exp(1.0f / duration));
-    } else {
-      initialized_ = true;
-      filter_.UpdateBase(exp(1.0f / time_constant_ms_));
-    }
-  }
-
-  // The filter will do the following:
-  //   float alpha = pow(base, last_update_time_ms_ - now_ms);
-  //   filtered_ = alpha * filtered_ + (1 - alpha) * sample;
-  filter_.Apply(static_cast<float>(last_sample_time_ms_ - now_ms), sample);
-  last_sample_time_ms_ = now_ms;
-}
-
-rtc::Optional<float> SmoothingFilterImpl::GetAverage() const {
-  float value = filter_.filtered();
-  return value == rtc::ExpFilter::kValueUndefined ? rtc::Optional<float>()
-                                                  : rtc::Optional<float>(value);
-}
-
-}  // namespace webrtc