1 files changed, 58 insertions, 0 deletions
diff --git a/dom/media/webrtc/SineWaveGenerator.h b/dom/media/webrtc/SineWaveGenerator.h
new file mode 100644
index 0000000000..73bab53f19
--- /dev/null
+++ b/dom/media/webrtc/SineWaveGenerator.h
@@ -0,0 +1,58 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef SINEWAVEGENERATOR_H_
+#define SINEWAVEGENERATOR_H_
+
+#include "MediaSegment.h"
+#include "prtime.h"
+
+namespace mozilla {
+
+// generate 1k sine wave per second
+template <typename Sample>
+class SineWaveGenerator {
+  static_assert(std::is_same<Sample, int16_t>::value ||
+                std::is_same<Sample, float>::value);
+
+ public:
+  static const int bytesPerSample = sizeof(Sample);
+  static const int millisecondsPerSecond = PR_MSEC_PER_SEC;
+  static constexpr float twopi = 2 * M_PI;
+
+  /* If more than 1 channel, generated samples are interleaved. */
+  SineWaveGenerator(uint32_t aSampleRate, uint32_t aFrequency)
+      : mPhase(0.), mPhaseIncrement(twopi * aFrequency / aSampleRate) {}
+
+  // NOTE: only safely called from a single thread (MTG callback)
+  void generate(Sample* aBuffer, TrackTicks aFrameCount,
+                uint32_t aChannelCount = 1) {
+    while (aFrameCount--) {
+      Sample value = sin(mPhase) * Amplitude();
+      for (uint32_t channel = 0; channel < aChannelCount; channel++) {
+        *aBuffer++ = value;
+      }
+      mPhase += mPhaseIncrement;
+      if (mPhase > twopi) {
+        mPhase -= twopi;
+      }
+    }
+  }
+
+  static float Amplitude() {
+    // Set volume to -20db.
+    if (std::is_same<Sample, int16_t>::value) {
+      return 3276.8;  // 32768.0 * 10^(-20/20) = 3276.8
+    }
+    return 0.1f;  // 1.0 * 10^(-20/20) = 0.1
+  }
+
+ private:
+  double mPhase;
+  const double mPhaseIncrement;
+};
+
+}  // namespace mozilla
+
+#endif /* SINEWAVEGENERATOR_H_ */