Source/WebCore/platform/audio/AudioUtilities.cpp

/*
 * 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
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 *    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
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "AudioUtilities.h"
#include <wtf/MathExtras.h>

namespace WebCore {

namespace AudioUtilities {

float decibelsToLinear(float decibels)
{
    return powf(10, 0.05f * decibels);
}

float linearToDecibels(float 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;
        
    return 20 * log10f(linear);
}

double discreteTimeConstantForSampleRate(double timeConstant, double sampleRate)
{
    return 1 - exp(-1 / (sampleRate * timeConstant));
}

size_t timeToSampleFrame(double time, double sampleRate)
{
    return static_cast<size_t>(round(time * sampleRate));
}
} // AudioUtilites

} // WebCore

#endif // ENABLE(WEB_AUDIO)