Source/platform/audio/AudioUtilities.cpp

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
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 *
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 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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#include "config.h"

#if ENABLE(WEB_AUDIO)

#include "platform/audio/AudioUtilities.h"

#include "wtf/Assertions.h"
#include "wtf/MathExtras.h"

namespace blink {

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)
{
    ASSERT(time >= 0);
    return static_cast<size_t>(round(time * sampleRate));
}

bool isValidAudioBufferSampleRate(float sampleRate)
{
    return sampleRate >= minAudioBufferSampleRate() && sampleRate <= maxAudioBufferSampleRate();
}

float minAudioBufferSampleRate()
{
    // crbug.com/344375
    return 3000;
}

float maxAudioBufferSampleRate()
{
    // Windows can support audio sampling rates this high, so allow AudioBuffer rates this high as well.
    return 192000;
}
} // AudioUtilites

} // namespace blink

#endif // ENABLE(WEB_AUDIO)