1 files changed, 63 insertions, 0 deletions
diff --git a/Source/WebCore/platform/audio/AudioUtilities.cpp b/Source/WebCore/platform/audio/AudioUtilities.cpp
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+++ b/Source/WebCore/platform/audio/AudioUtilities.cpp
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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.
+ */
+
+#include "config.h"
+
+#if ENABLE(WEB_AUDIO)
+
+#include "AudioUtilities.h"
+#include <wtf/MathExtras.h>
+
+namespace WebCore {
+
+namespace AudioUtilities {
+
+double decibelsToLinear(double decibels)
+{
+    return pow(10.0, 0.05 * decibels);
+}
+
+double linearToDecibels(double linear)
+{
+    // It's not possible to calculate decibels for a zero linear value since it would be -Inf.
+    // -1000.0 dB represents a very tiny linear value in case we ever reach this case.
+    ASSERT(linear);
+    if (!linear)
+        return -1000.0;
+        
+    return 20.0 * log10(linear);
+}
+
+double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate)
+{
+    // hardcoded value is temporary build fix for Windows.
+    // FIXME: replace hardcode 2.718282 with M_E until the correct MathExtras.h solution is determined.
+    return 1.0 - pow(1.0 / 2.718282, 1.0 / (sampleRate * timeConstant));
+}
+    
+} // AudioUtilites
+
+} // WebCore
+
+#endif // ENABLE(WEB_AUDIO)