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/*
* 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 SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#if ENABLE(WEB_AUDIO)
#include "EqualPowerPanner.h"
#include "AudioBus.h"
#include "AudioUtilities.h"
#include <algorithm>
#include <wtf/MathExtras.h>
// Use a 50ms smoothing / de-zippering time-constant.
const float SmoothingTimeConstant = 0.050f;
using namespace std;
namespace WebCore {
EqualPowerPanner::EqualPowerPanner(float sampleRate)
: Panner(PanningModelEqualPower)
, m_isFirstRender(true)
, m_gainL(0.0)
, m_gainR(0.0)
{
m_smoothingConstant = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate);
}
void EqualPowerPanner::pan(double azimuth, double /*elevation*/, const AudioBus* inputBus, AudioBus* outputBus, size_t framesToProcess)
{
// FIXME: implement stereo sources
bool isInputSafe = inputBus && inputBus->numberOfChannels() == 1 && framesToProcess <= inputBus->length();
ASSERT(isInputSafe);
if (!isInputSafe)
return;
bool isOutputSafe = outputBus && outputBus->numberOfChannels() == 2 && framesToProcess <= outputBus->length();
ASSERT(isOutputSafe);
if (!isOutputSafe)
return;
const AudioChannel* channel = inputBus->channel(0);
const float* sourceP = channel->data();
float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->mutableData();
float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->mutableData();
if (!sourceP || !destinationL || !destinationR)
return;
// Clamp azimuth to allowed range of -180 -> +180.
azimuth = max(-180.0, azimuth);
azimuth = min(180.0, azimuth);
// Alias the azimuth ranges behind us to in front of us:
// -90 -> -180 to -90 -> 0 and 90 -> 180 to 90 -> 0
if (azimuth < -90)
azimuth = -180 - azimuth;
else if (azimuth > 90)
azimuth = 180 - azimuth;
// Pan smoothly from left to right with azimuth going from -90 -> +90 degrees.
double desiredPanPosition = (azimuth + 90) / 180;
double desiredGainL = cos(0.5 * piDouble * desiredPanPosition);
double desiredGainR = sin(0.5 * piDouble * desiredPanPosition);
// Don't de-zipper on first render call.
if (m_isFirstRender) {
m_isFirstRender = false;
m_gainL = desiredGainL;
m_gainR = desiredGainR;
}
// Cache in local variables.
double gainL = m_gainL;
double gainR = m_gainR;
// Get local copy of smoothing constant.
const double SmoothingConstant = m_smoothingConstant;
int n = framesToProcess;
while (n--) {
float input = *sourceP++;
gainL += (desiredGainL - gainL) * SmoothingConstant;
gainR += (desiredGainR - gainR) * SmoothingConstant;
*destinationL++ = static_cast<float>(input * gainL);
*destinationR++ = static_cast<float>(input * gainR);
}
m_gainL = gainL;
m_gainR = gainR;
}
} // namespace WebCore
#endif // ENABLE(WEB_AUDIO)
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