1 files changed, 78 insertions, 0 deletions
diff --git a/dom/media/webaudio/blink/ZeroPole.cpp b/dom/media/webaudio/blink/ZeroPole.cpp
new file mode 100644
index 000000000..ac0b15c7a
--- /dev/null
+++ b/dom/media/webaudio/blink/ZeroPole.cpp
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+/*
+ * Copyright (C) 2011 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.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE 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 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 "ZeroPole.h"
+
+#include <cmath>
+#include <float.h>
+
+namespace WebCore {
+
+void ZeroPole::process(const float *source, float *destination, int framesToProcess)
+{
+    float zero = m_zero;
+    float pole = m_pole;
+
+    // Gain compensation to make 0dB @ 0Hz
+    const float k1 = 1 / (1 - zero);
+    const float k2 = 1 - pole;
+    
+    // Member variables to locals.
+    float lastX = m_lastX;
+    float lastY = m_lastY;
+
+    for (int i = 0; i < framesToProcess; ++i) {
+        float input = source[i];
+
+        // Zero
+        float output1 = k1 * (input - zero * lastX);
+        lastX = input;
+
+        // Pole
+        float output2 = k2 * output1 + pole * lastY;
+        lastY = output2;
+
+        destination[i] = output2;
+    }
+    
+    // Locals to member variables. Flush denormals here so we don't
+    // slow down the inner loop above.
+    if (lastX == 0.0f && lastY != 0.0f && fabsf(lastY) < FLT_MIN) {
+        // Flush future values to zero (until there is new input).
+        lastY = 0.0;
+        // Flush calculated values.
+        for (int i = framesToProcess; i-- && fabsf(destination[i]) < FLT_MIN; ) {
+            destination[i] = 0.0f;
+        }
+    }
+
+    m_lastX = lastX;
+    m_lastY = lastY;
+}
+
+} // namespace WebCore