Adding full initial version of delay estimation functionality in echo canceller 3

webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc

Index: webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc
diff --git a/webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc b/webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d9176efa94fbd76f6d2fbbffa121e7ba2f68e54d
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+++ b/webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.cc
@@ -0,0 +1,66 @@
+/*
+ *  Copyright (c) 2017 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/modules/audio_processing/aec3/matched_filter_lag_aggregator.h"
+
+#include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
+
+namespace webrtc {
+
+MatchedFilterLagAggregator::MatchedFilterLagAggregator(
+    ApmDataDumper* data_dumper,
+    size_t num_lag_estimates)
+    : data_dumper_(data_dumper), lag_updates_in_a_row_(num_lag_estimates, 0) {
+  RTC_DCHECK(data_dumper);
+  RTC_DCHECK_LT(0, num_lag_estimates);
+}
+
+MatchedFilterLagAggregator::~MatchedFilterLagAggregator() = default;
+
+rtc::Optional<size_t> MatchedFilterLagAggregator::Aggregate(
+    rtc::ArrayView<const MatchedFilter::LagEstimate> lag_estimates) {
+  RTC_DCHECK_EQ(lag_updates_in_a_row_.size(), lag_estimates.size());
+
+  // Count the number of lag updates in a row to ensure that only stable lags
+  // are taken into account.
+  for (size_t k = 0; k < lag_estimates.size(); ++k) {
+    lag_updates_in_a_row_[k] =
+        lag_estimates[k].updated ? lag_updates_in_a_row_[k] + 1 : 0;
+  }
+
+  // If available, choose the strongest lag estimate as the best one.
+  int best_lag_estimate_index = -1;
+  for (size_t k = 0; k < lag_estimates.size(); ++k) {
+    if (lag_updates_in_a_row_[k] > 10 && lag_estimates[k].reliable &&
+        (best_lag_estimate_index == -1 ||
+         lag_estimates[k].accuracy >
+             lag_estimates[best_lag_estimate_index].accuracy)) {
+      best_lag_estimate_index = k;
+    }
+  }
+
+  // TODO(peah): Remove this logging once all development is done.
+  data_dumper_->DumpRaw("aec3_echo_path_delay_estimator_best_index",
+                        best_lag_estimate_index);
+
+  // Require the same lag to be detected 10 times in a row before considering
+  // it reliable.
+  if (best_lag_estimate_index >= 0) {
+    candidate_counter_ =
+        (candidate_ == lag_estimates[best_lag_estimate_index].lag)
+            ? candidate_counter_ + 1
+            : 0;
+    candidate_ = lag_estimates[best_lag_estimate_index].lag;
+  }
+
+  return candidate_counter_ >= 10 ? rtc::Optional<size_t>(candidate_)
+                                  : rtc::Optional<size_t>();
+}
+
+}  // namespace webrtc