1 files changed, 67 insertions, 0 deletions
diff --git a/externals/oboe/src/flowgraph/Limiter.cpp b/externals/oboe/src/flowgraph/Limiter.cpp
new file mode 100644
index 0000000000..def905a752
--- /dev/null
+++ b/externals/oboe/src/flowgraph/Limiter.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2022 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 <algorithm>
+#include <math.h>
+#include <unistd.h>
+#include "FlowGraphNode.h"
+#include "Limiter.h"
+
+using namespace FLOWGRAPH_OUTER_NAMESPACE::flowgraph;
+
+Limiter::Limiter(int32_t channelCount)
+        : FlowGraphFilter(channelCount) {
+}
+
+int32_t Limiter::onProcess(int32_t numFrames) {
+    const float *inputBuffer = input.getBuffer();
+    float *outputBuffer = output.getBuffer();
+
+    int32_t numSamples = numFrames * output.getSamplesPerFrame();
+
+    // Cache the last valid output to reduce memory read/write
+    float lastValidOutput = mLastValidOutput;
+
+    for (int32_t i = 0; i < numSamples; i++) {
+        // Use the previous output if the input is NaN
+        if (!isnan(*inputBuffer)) {
+            lastValidOutput = processFloat(*inputBuffer);
+        }
+        inputBuffer++;
+        *outputBuffer++ = lastValidOutput;
+    }
+    mLastValidOutput = lastValidOutput;
+
+    return numFrames;
+}
+
+float Limiter::processFloat(float in)
+{
+    float in_abs = fabsf(in);
+    if (in_abs <= 1) {
+        return in;
+    }
+    float out;
+    if (in_abs < kXWhenYis3Decibels) {
+        out = (kPolynomialSplineA * in_abs + kPolynomialSplineB) * in_abs + kPolynomialSplineC;
+    } else {
+        out = M_SQRT2;
+    }
+    if (in < 0) {
+        out = -out;
+    }
+    return out;
+}