gecko-dev/content/media/webaudio/WebAudioUtils.h

76 lines
2.0 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef WebAudioUtils_h_
#define WebAudioUtils_h_
#include <cmath>
#include "AudioParamTimeline.h"
namespace mozilla {
class AudioNodeStream;
namespace dom {
struct WebAudioUtils {
static bool FuzzyEqual(float v1, float v2)
{
using namespace std;
return fabsf(v1 - v2) < 1e-7f;
}
static bool FuzzyEqual(double v1, double v2)
{
using namespace std;
return fabs(v1 - v2) < 1e-7;
}
/**
* Computes an exponential smoothing rate for a time based variable
* over aDuration seconds.
*/
static double ComputeSmoothingRate(double aDuration, double aSampleRate)
{
return 1.0 - std::exp(-1.0 / (aDuration * aSampleRate));
}
/**
* Converts AudioParamTimeline floating point time values to tick values
* with respect to a source and a destination AudioNodeStream.
*
* This needs to be called for each AudioParamTimeline that gets sent to an
* AudioNodeEngine on the engine side where the AudioParamTimeline is
* received. This means that such engines need to be aware of their source
* and destination streams as well.
*/
static void ConvertAudioParamToTicks(AudioParamTimeline& aParam,
AudioNodeStream* aSource,
AudioNodeStream* aDest);
/**
* Converts a linear value to decibels. Returns aMinDecibels if the linear
* value is 0.
*/
static float ConvertLinearToDecibels(float aLinearValue, float aMinDecibels)
{
return aLinearValue ? 20.0f * std::log10(aLinearValue) : aMinDecibels;
}
/**
* Converts a decibel to a linear value.
*/
static float ConvertDecibelToLinear(float aDecibel)
{
return std::pow(10.0f, 0.05f * aDecibel);
}
};
}
}
#endif