1 files changed, 104 insertions, 0 deletions
diff --git a/third_party/libwebrtc/video/quality_threshold.cc b/third_party/libwebrtc/video/quality_threshold.cc
new file mode 100644
index 0000000000..931b0b20f9
--- /dev/null
+++ b/third_party/libwebrtc/video/quality_threshold.cc
@@ -0,0 +1,104 @@
+/*
+ *  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 "video/quality_threshold.h"
+
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+
+QualityThreshold::QualityThreshold(int low_threshold,
+                                   int high_threshold,
+                                   float fraction,
+                                   int max_measurements)
+    : buffer_(new int[max_measurements]),
+      max_measurements_(max_measurements),
+      fraction_(fraction),
+      low_threshold_(low_threshold),
+      high_threshold_(high_threshold),
+      until_full_(max_measurements),
+      next_index_(0),
+      sum_(0),
+      count_low_(0),
+      count_high_(0),
+      num_high_states_(0),
+      num_certain_states_(0) {
+  RTC_CHECK_GT(fraction, 0.5f);
+  RTC_CHECK_GT(max_measurements, 1);
+  RTC_CHECK_LT(low_threshold, high_threshold);
+}
+
+QualityThreshold::~QualityThreshold() = default;
+
+void QualityThreshold::AddMeasurement(int measurement) {
+  int prev_val = until_full_ > 0 ? 0 : buffer_[next_index_];
+  buffer_[next_index_] = measurement;
+  next_index_ = (next_index_ + 1) % max_measurements_;
+
+  sum_ += measurement - prev_val;
+
+  if (until_full_ == 0) {
+    if (prev_val <= low_threshold_) {
+      --count_low_;
+    } else if (prev_val >= high_threshold_) {
+      --count_high_;
+    }
+  }
+
+  if (measurement <= low_threshold_) {
+    ++count_low_;
+  } else if (measurement >= high_threshold_) {
+    ++count_high_;
+  }
+
+  float sufficient_majority = fraction_ * max_measurements_;
+  if (count_high_ >= sufficient_majority) {
+    is_high_ = true;
+  } else if (count_low_ >= sufficient_majority) {
+    is_high_ = false;
+  }
+
+  if (until_full_ > 0)
+    --until_full_;
+
+  if (is_high_) {
+    if (*is_high_)
+      ++num_high_states_;
+    ++num_certain_states_;
+  }
+}
+
+absl::optional<bool> QualityThreshold::IsHigh() const {
+  return is_high_;
+}
+
+absl::optional<double> QualityThreshold::CalculateVariance() const {
+  if (until_full_ > 0) {
+    return absl::nullopt;
+  }
+
+  double variance = 0;
+  double mean = static_cast<double>(sum_) / max_measurements_;
+  for (int i = 0; i < max_measurements_; ++i) {
+    variance += (buffer_[i] - mean) * (buffer_[i] - mean);
+  }
+  return variance / (max_measurements_ - 1);
+}
+
+absl::optional<double> QualityThreshold::FractionHigh(
+    int min_required_samples) const {
+  RTC_DCHECK_GT(min_required_samples, 0);
+  if (num_certain_states_ < min_required_samples)
+    return absl::nullopt;
+
+  return static_cast<double>(num_high_states_) / num_certain_states_;
+}
+
+}  // namespace webrtc