Send data from mixer to APM limiter more often.

webrtc/modules/audio_mixer/gain_change_calculator.cc

Index: webrtc/modules/audio_mixer/gain_change_calculator.cc
diff --git a/webrtc/modules/audio_mixer/gain_change_calculator.cc b/webrtc/modules/audio_mixer/gain_change_calculator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..13017d4220b5b7c41f8f500a198204e4cd0bc879
--- /dev/null
+++ b/webrtc/modules/audio_mixer/gain_change_calculator.cc
@@ -0,0 +1,55 @@
+/*
+ *  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_mixer/gain_change_calculator.h"
+
+#include <math.h>
+#include <vector>
+
+namespace webrtc {
+
+namespace {
+constexpr int16_t kReliabilityThreshold = 100;
+}  // namespace
+
+float GainChangeCalculator::CalculateGainChange(
+    rtc::ArrayView<const int16_t> in,
+    rtc::ArrayView<const int16_t> out) {
+  RTC_DCHECK_EQ(in.size(), out.size());
+
+  std::vector<float> gain(in.size());
+  CalculateGain(in, out, gain);
+  return CalculateDifferences(gain);
+}
+
+void GainChangeCalculator::CalculateGain(rtc::ArrayView<const int16_t> in,
+                                         rtc::ArrayView<const int16_t> out,
+                                         rtc::ArrayView<float> gain) {
+  RTC_DCHECK_EQ(in.size(), out.size());
+  RTC_DCHECK_EQ(in.size(), gain.size());
+
+  for (size_t i = 0; i < in.size(); ++i) {
+    if (std::abs(in[i]) >= kReliabilityThreshold) {
+      last_reliable_gain_ = out[i] / static_cast<float>(in[i]);
+    }
+    gain[i] = last_reliable_gain_;
+  }
+}
+
+float GainChangeCalculator::CalculateDifferences(
+    rtc::ArrayView<const float> values) {
+  float res = 0;
+  for (float f : values) {
+    res += fabs(f - last_value_);
+    last_value_ = f;
+  }
+  return res;
+}
+}  // namespace webrtc