third_party/WebKit/Source/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
 * 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.
 *
 * 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 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 */

#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) {
  ASSERT(linear >= 0);

  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);
  double frame = round(time * sampleRate);

  // Just return the largest possible size_t value if necessary.
  if (frame >= std::numeric_limits<size_t>::max()) {
    return std::numeric_limits<size_t>::max();
  }

  return static_cast<size_t>(frame);
}

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;
}
}  // namespace AudioUtilities

}  // namespace blink