1 files changed, 88 insertions, 0 deletions
diff --git a/externals/oboe/apps/OboeTester/app/src/main/cpp/analyzer/RoundedManchesterEncoder.h b/externals/oboe/apps/OboeTester/app/src/main/cpp/analyzer/RoundedManchesterEncoder.h
new file mode 100644
index 0000000000..51461526ce
--- /dev/null
+++ b/externals/oboe/apps/OboeTester/app/src/main/cpp/analyzer/RoundedManchesterEncoder.h
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2019 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.
+ */
+
+#ifndef ANALYZER_ROUNDED_MANCHESTER_ENCODER_H
+#define ANALYZER_ROUNDED_MANCHESTER_ENCODER_H
+
+#include <math.h>
+#include <memory>
+#include <stdlib.h>
+#include "ManchesterEncoder.h"
+
+/**
+ * Encode bytes using Manchester Code.
+ * Round the edges using a half cosine to reduce ringing caused by a hard edge.
+ */
+
+class RoundedManchesterEncoder : public ManchesterEncoder {
+public:
+    RoundedManchesterEncoder(int samplesPerPulse)
+            : ManchesterEncoder(samplesPerPulse) {
+        int rampSize = samplesPerPulse / 4;
+        mZeroAfterZero = std::make_unique<float[]>(samplesPerPulse);
+        mZeroAfterOne = std::make_unique<float[]>(samplesPerPulse);
+
+        int sampleIndex = 0;
+        for (int rampIndex = 0; rampIndex < rampSize; rampIndex++) {
+            float phase = (rampIndex + 1) * M_PI / rampSize;
+            float sample = -cosf(phase);
+            mZeroAfterZero[sampleIndex] = sample;
+            mZeroAfterOne[sampleIndex] = 1.0f;
+            sampleIndex++;
+        }
+        for (int rampIndex = 0; rampIndex < rampSize; rampIndex++) {
+            mZeroAfterZero[sampleIndex] = 1.0f;
+            mZeroAfterOne[sampleIndex] = 1.0f;
+            sampleIndex++;
+        }
+        for (int rampIndex = 0; rampIndex < rampSize; rampIndex++) {
+            float phase = (rampIndex + 1) * M_PI / rampSize;
+            float sample = cosf(phase);
+            mZeroAfterZero[sampleIndex] = sample;
+            mZeroAfterOne[sampleIndex] = sample;
+            sampleIndex++;
+        }
+        for (int rampIndex = 0; rampIndex < rampSize; rampIndex++) {
+            mZeroAfterZero[sampleIndex] = -1.0f;
+            mZeroAfterOne[sampleIndex] = -1.0f;
+            sampleIndex++;
+        }
+    }
+
+    void onNextBit(bool current) override {
+        // Do we need to use the rounded edge?
+        mCurrentSamples = (current ^ mPreviousBit)
+                          ? mZeroAfterOne.get()
+                          : mZeroAfterZero.get();
+        mPreviousBit = current;
+    }
+
+    float nextFloat() override {
+        advanceSample();
+        float output = mCurrentSamples[mCursor];
+        if (getCurrentBit()) output = -output;
+        return output;
+    }
+
+private:
+
+    bool mPreviousBit = false;
+    float *mCurrentSamples = nullptr;
+    std::unique_ptr<float[]> mZeroAfterZero;
+    std::unique_ptr<float[]> mZeroAfterOne;
+};
+
+#endif //ANALYZER_ROUNDED_MANCHESTER_ENCODER_H