Send data from mixer to APM limiter more often.

webrtc/modules/audio_mixer/frame_combiner_test_tools.cc

+/*
+ *  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 <cmath>
+#include <numeric>
+#include <vector>
+
+#include "webrtc/base/logging.h"
+#include "webrtc/base/safe_conversions.h"
+#include "webrtc/modules/audio_mixer/frame_combiner_test_tools.h"
+
+namespace webrtc {
+
+namespace {
+constexpr float kPi = 3.14159265;
+constexpr int16_t kReliabilityThreshold = 100;
+}
+
+void SineWaveGenerator::GenerateNextFrame(AudioFrame* frame) {

[ivoc, 2017/03/28 16:11:06]

Please add DCHECK(frame)

+  for (size_t i = 0; i < frame->samples_per_channel_; ++i) {
+    for (size_t ch = 0; ch < frame->num_channels_; ++ch) {
+      frame->data_[frame->num_channels_ * i + ch] =
+          rtc::saturated_cast<int16_t>(amplitude_ * sin(phase_));

[ivoc, 2017/03/28 16:11:06]

sinf, sin is for doubles.

[aleloi, 2017/03/28 17:10:13]

Done.

+    }
+    phase_ += wave_frequency_hz_ * 2 * kPi / frame->sample_rate_hz_;
+  }
+}
+
+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());
+  auto gain_view = rtc::ArrayView<float>(gain.data(), gain.size());
+  CalculateGain(in, out, gain_view);
+  return CalculateDifferences(gain_view);
+}
+
+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) {

[ivoc, 2017/03/28 16:11:06]

Won't this cause some discontinuities in the calculated gain? Or is it not a
problem in practice?

[aleloi, 2017/03/28 17:10:13]

If the threshold increases, the resulted sum of differences can only decrease.
With higher threshold the test will be easier to pass, not harder. That may be a
problem with the test, though.

+      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 += std::abs(f - last_value_);

[ivoc, 2017/03/28 16:11:06]

fabs, abs is for ints.

[aleloi, 2017/03/28 17:10:13]

I checked that this returns floats. fabs seems more safe, though.

http://en.cppreference.com/w/cpp/numeric/math/fabs 

+    last_value_ = f;
+  }
+  return res;
+}
+}  // namespace webrtc