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diff --git a/Source/WebCore/platform/audio/EqualPowerPanner.h b/Source/WebCore/platform/audio/EqualPowerPanner.h
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+/*
+ * Copyright (C) 2010, Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1.  Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef EqualPowerPanner_h
+#define EqualPowerPanner_h
+
+#include "Panner.h"
+
+namespace WebCore {
+
+// Common type of stereo panner as found in normal audio mixing equipment.
+
+class EqualPowerPanner : public Panner {
+public:
+    EqualPowerPanner(double sampleRate);
+
+    virtual void pan(double azimuth, double elevation, AudioBus* inputBus, AudioBus* outputBuf, size_t framesToProcess);
+
+    virtual void reset() { m_isFirstRender = true; }
+
+private:
+    // For smoothing / de-zippering
+    bool m_isFirstRender;
+    double m_smoothingConstant;
+    
+    double m_gainL;
+    double m_gainR;
+};
+
+} // namespace WebCore
+
+#endif // EqualPowerPanner_h