1 files changed, 141 insertions, 0 deletions
diff --git a/media/libeffects/loudness/dsp/core/dynamic_range_compression.cpp b/media/libeffects/loudness/dsp/core/dynamic_range_compression.cpp
new file mode 100644
index 0000000..7bd068e
--- /dev/null
+++ b/media/libeffects/loudness/dsp/core/dynamic_range_compression.cpp
@@ -0,0 +1,141 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cmath>
+
+#include "common/core/math.h"
+#include "common/core/types.h"
+#include "dsp/core/basic.h"
+#include "dsp/core/interpolation.h"
+#include "dsp/core/dynamic_range_compression.h"
+
+//#define LOG_NDEBUG 0
+#include <cutils/log.h>
+
+
+namespace le_fx {
+
+// Definitions for static const class members declared in
+// dynamic_range_compression.h.
+const float AdaptiveDynamicRangeCompression::kMinAbsValue = 0.000001f;
+const float AdaptiveDynamicRangeCompression::kMinLogAbsValue =
+    0.032766999999999997517097227728299912996590137481689453125f;
+const float AdaptiveDynamicRangeCompression::kFixedPointLimit = 32767.0f;
+const float AdaptiveDynamicRangeCompression::kInverseFixedPointLimit =
+    1.0f / AdaptiveDynamicRangeCompression::kFixedPointLimit;
+const float AdaptiveDynamicRangeCompression::kDefaultKneeThresholdInDecibel =
+    -8.0f;
+const float AdaptiveDynamicRangeCompression::kCompressionRatio = 7.0f;
+const float AdaptiveDynamicRangeCompression::kTauAttack = 0.001f;
+const float AdaptiveDynamicRangeCompression::kTauRelease = 0.015f;
+
+AdaptiveDynamicRangeCompression::AdaptiveDynamicRangeCompression() {
+  static const float kTargetGain[] = {
+      1.0f, 2.0f, 3.0f, 4.0f, 5.0f };
+  static const float kKneeThreshold[] = {
+      -8.0f, -8.0f, -8.5f, -9.0f, -10.0f };
+  target_gain_to_knee_threshold_.Initialize(
+      &kTargetGain[0], &kKneeThreshold[0],
+      sizeof(kTargetGain) / sizeof(kTargetGain[0]));
+}
+
+bool AdaptiveDynamicRangeCompression::Initialize(
+        float target_gain, float sampling_rate) {
+  set_knee_threshold_via_target_gain(target_gain);
+  sampling_rate_ = sampling_rate;
+  state_ = 0.0f;
+  compressor_gain_ = 1.0f;
+  if (kTauAttack > 0.0f) {
+    const float taufs = kTauAttack * sampling_rate_;
+    alpha_attack_ = std::exp(-1.0f / taufs);
+  } else {
+    alpha_attack_ = 0.0f;
+  }
+  if (kTauRelease > 0.0f) {
+    const float taufs = kTauRelease * sampling_rate_;
+    alpha_release_ = std::exp(-1.0f / taufs);
+  } else {
+    alpha_release_ = 0.0f;
+  }
+  // Feed-forward topology
+  slope_ = 1.0f / kCompressionRatio - 1.0f;
+  return true;
+}
+
+float AdaptiveDynamicRangeCompression::Compress(float x) {
+  const float max_abs_x = std::max(std::fabs(x), kMinLogAbsValue);
+  const float max_abs_x_dB = math::fast_log(max_abs_x);
+  // Subtract Threshold from log-encoded input to get the amount of overshoot
+  const float overshoot = max_abs_x_dB - knee_threshold_;
+  // Hard half-wave rectifier
+  const float rect = std::max(overshoot, 0.0f);
+  // Multiply rectified overshoot with slope
+  const float cv = rect * slope_;
+  const float prev_state = state_;
+  if (cv <= state_) {
+    state_ = alpha_attack_ * state_ + (1.0f - alpha_attack_) * cv;
+  } else {
+    state_ = alpha_release_ * state_ + (1.0f - alpha_release_) * cv;
+  }
+  compressor_gain_ *=
+      math::ExpApproximationViaTaylorExpansionOrder5(state_ - prev_state);
+  x *= compressor_gain_;
+  if (x > kFixedPointLimit) {
+    return kFixedPointLimit;
+  }
+  if (x < -kFixedPointLimit) {
+    return -kFixedPointLimit;
+  }
+  return x;
+}
+
+void AdaptiveDynamicRangeCompression::Compress(float *x1, float *x2) {
+  // Taking the maximum amplitude of both channels
+  const float max_abs_x = std::max(std::fabs(*x1),
+    std::max(std::fabs(*x2), kMinLogAbsValue));
+  const float max_abs_x_dB = math::fast_log(max_abs_x);
+  // Subtract Threshold from log-encoded input to get the amount of overshoot
+  const float overshoot = max_abs_x_dB - knee_threshold_;
+  // Hard half-wave rectifier
+  const float rect = std::max(overshoot, 0.0f);
+  // Multiply rectified overshoot with slope
+  const float cv = rect * slope_;
+  const float prev_state = state_;
+  if (cv <= state_) {
+    state_ = alpha_attack_ * state_ + (1.0f - alpha_attack_) * cv;
+  } else {
+    state_ = alpha_release_ * state_ + (1.0f - alpha_release_) * cv;
+  }
+  compressor_gain_ *=
+      math::ExpApproximationViaTaylorExpansionOrder5(state_ - prev_state);
+  *x1 *= compressor_gain_;
+  if (*x1 > kFixedPointLimit) {
+    *x1 = kFixedPointLimit;
+  }
+  if (*x1 < -kFixedPointLimit) {
+    *x1 = -kFixedPointLimit;
+  }
+  *x2 *= compressor_gain_;
+  if (*x2 > kFixedPointLimit) {
+    *x2 = kFixedPointLimit;
+  }
+  if (*x2 < -kFixedPointLimit) {
+    *x2 = -kFixedPointLimit;
+  }
+}
+
+}  // namespace le_fx
+