1 files changed, 121 insertions, 0 deletions
diff --git a/webrtc/modules/audio_processing/agc2/saturation_protector.cc b/webrtc/modules/audio_processing/agc2/saturation_protector.cc
new file mode 100644
index 0000000..b64fcdb
--- /dev/null
+++ b/webrtc/modules/audio_processing/agc2/saturation_protector.cc
@@ -0,0 +1,121 @@
+/*
+ *  Copyright (c) 2018 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 "modules/audio_processing/agc2/saturation_protector.h"
+
+#include "modules/audio_processing/logging/apm_data_dumper.h"
+#include "rtc_base/numerics/safe_minmax.h"
+
+namespace webrtc {
+namespace {
+
+constexpr float kMinLevelDbfs = -90.f;
+
+// Min/max margins are based on speech crest-factor.
+constexpr float kMinMarginDb = 12.f;
+constexpr float kMaxMarginDb = 25.f;
+
+using saturation_protector_impl::RingBuffer;
+
+}  // namespace
+
+bool RingBuffer::operator==(const RingBuffer& b) const {
+  RTC_DCHECK_LE(size_, buffer_.size());
+  RTC_DCHECK_LE(b.size_, b.buffer_.size());
+  if (size_ != b.size_) {
+    return false;
+  }
+  for (int i = 0, i0 = FrontIndex(), i1 = b.FrontIndex(); i < size_;
+       ++i, ++i0, ++i1) {
+    if (buffer_[i0 % buffer_.size()] != b.buffer_[i1 % b.buffer_.size()]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+void RingBuffer::Reset() {
+  next_ = 0;
+  size_ = 0;
+}
+
+void RingBuffer::PushBack(float v) {
+  RTC_DCHECK_GE(next_, 0);
+  RTC_DCHECK_GE(size_, 0);
+  RTC_DCHECK_LT(next_, buffer_.size());
+  RTC_DCHECK_LE(size_, buffer_.size());
+  buffer_[next_++] = v;
+  if (rtc::SafeEq(next_, buffer_.size())) {
+    next_ = 0;
+  }
+  if (rtc::SafeLt(size_, buffer_.size())) {
+    size_++;
+  }
+}
+
+absl::optional<float> RingBuffer::Front() const {
+  if (size_ == 0) {
+    return absl::nullopt;
+  }
+  RTC_DCHECK_LT(FrontIndex(), buffer_.size());
+  return buffer_[FrontIndex()];
+}
+
+bool SaturationProtectorState::operator==(
+    const SaturationProtectorState& b) const {
+  return margin_db == b.margin_db && peak_delay_buffer == b.peak_delay_buffer &&
+         max_peaks_dbfs == b.max_peaks_dbfs &&
+         time_since_push_ms == b.time_since_push_ms;
+}
+
+void ResetSaturationProtectorState(float initial_margin_db,
+                                   SaturationProtectorState& state) {
+  state.margin_db = initial_margin_db;
+  state.peak_delay_buffer.Reset();
+  state.max_peaks_dbfs = kMinLevelDbfs;
+  state.time_since_push_ms = 0;
+}
+
+void UpdateSaturationProtectorState(float speech_peak_dbfs,
+                                    float speech_level_dbfs,
+                                    SaturationProtectorState& state) {
+  // Get the max peak over `kPeakEnveloperSuperFrameLengthMs` ms.
+  state.max_peaks_dbfs = std::max(state.max_peaks_dbfs, speech_peak_dbfs);
+  state.time_since_push_ms += kFrameDurationMs;
+  if (rtc::SafeGt(state.time_since_push_ms, kPeakEnveloperSuperFrameLengthMs)) {
+    // Push `max_peaks_dbfs` back into the ring buffer.
+    state.peak_delay_buffer.PushBack(state.max_peaks_dbfs);
+    // Reset.
+    state.max_peaks_dbfs = kMinLevelDbfs;
+    state.time_since_push_ms = 0;
+  }
+
+  // Update margin by comparing the estimated speech level and the delayed max
+  // speech peak power.
+  // TODO(alessiob): Check with aleloi@ why we use a delay and how to tune it.
+  const float delayed_peak_dbfs =
+      state.peak_delay_buffer.Front().value_or(state.max_peaks_dbfs);
+  const float difference_db = delayed_peak_dbfs - speech_level_dbfs;
+  if (difference_db > state.margin_db) {
+    // Attack.
+    state.margin_db =
+        state.margin_db * kSaturationProtectorAttackConstant +
+        difference_db * (1.f - kSaturationProtectorAttackConstant);
+  } else {
+    // Decay.
+    state.margin_db = state.margin_db * kSaturationProtectorDecayConstant +
+                      difference_db * (1.f - kSaturationProtectorDecayConstant);
+  }
+
+  state.margin_db =
+      rtc::SafeClamp<float>(state.margin_db, kMinMarginDb, kMaxMarginDb);
+}
+
+}  // namespace webrtc