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diff --git a/portaudio/src/common/pa_cpuload.c b/portaudio/src/common/pa_cpuload.c
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+++ b/portaudio/src/common/pa_cpuload.c
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+/*
+ * $Id$
+ * Portable Audio I/O Library CPU Load measurement functions
+ * Portable CPU load measurement facility.
+ *
+ * Based on the Open Source API proposed by Ross Bencina
+ * Copyright (c) 2002 Ross Bencina
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+ * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * The text above constitutes the entire PortAudio license; however,
+ * the PortAudio community also makes the following non-binding requests:
+ *
+ * Any person wishing to distribute modifications to the Software is
+ * requested to send the modifications to the original developer so that
+ * they can be incorporated into the canonical version. It is also
+ * requested that these non-binding requests be included along with the
+ * license above.
+ */
+
+/** @file
+ @ingroup common_src
+
+ @brief Functions to assist in measuring the CPU utilization of a callback
+ stream. Used to implement the Pa_GetStreamCpuLoad() function.
+
+ @todo Dynamically calculate the coefficients used to smooth the CPU Load
+ Measurements over time to provide a uniform characterisation of CPU Load
+ independent of rate at which PaUtil_BeginCpuLoadMeasurement /
+ PaUtil_EndCpuLoadMeasurement are called. see http://www.portaudio.com/trac/ticket/113
+*/
+
+
+#include "pa_cpuload.h"
+
+#include <assert.h>
+
+#include "pa_util.h"   /* for PaUtil_GetTime() */
+
+
+void PaUtil_InitializeCpuLoadMeasurer( PaUtilCpuLoadMeasurer* measurer, double sampleRate )
+{
+    assert( sampleRate > 0 );
+
+    measurer->samplingPeriod = 1. / sampleRate;
+    measurer->averageLoad = 0.;
+}
+
+void PaUtil_ResetCpuLoadMeasurer( PaUtilCpuLoadMeasurer* measurer )
+{
+    measurer->averageLoad = 0.;
+}
+
+void PaUtil_BeginCpuLoadMeasurement( PaUtilCpuLoadMeasurer* measurer )
+{
+    measurer->measurementStartTime = PaUtil_GetTime();
+}
+
+
+void PaUtil_EndCpuLoadMeasurement( PaUtilCpuLoadMeasurer* measurer, unsigned long framesProcessed )
+{
+    double measurementEndTime, secondsFor100Percent, measuredLoad;
+
+    if( framesProcessed > 0 ){
+        measurementEndTime = PaUtil_GetTime();
+
+        assert( framesProcessed > 0 );
+        secondsFor100Percent = framesProcessed * measurer->samplingPeriod;
+
+        measuredLoad = (measurementEndTime - measurer->measurementStartTime) / secondsFor100Percent;
+
+        /* Low pass filter the calculated CPU load to reduce jitter using a simple IIR low pass filter. */
+        /** FIXME @todo these coefficients shouldn't be hardwired see: http://www.portaudio.com/trac/ticket/113 */
+#define LOWPASS_COEFFICIENT_0   (0.9)
+#define LOWPASS_COEFFICIENT_1   (0.99999 - LOWPASS_COEFFICIENT_0)
+
+        measurer->averageLoad = (LOWPASS_COEFFICIENT_0 * measurer->averageLoad) +
+                                (LOWPASS_COEFFICIENT_1 * measuredLoad);
+    }
+}
+
+
+double PaUtil_GetCpuLoad( PaUtilCpuLoadMeasurer* measurer )
+{
+    return measurer->averageLoad;
+}