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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "config.h"
#if ENABLE(WEB_AUDIO)
#include "platform/audio/StereoPanner.h"
#include "platform/audio/AudioBus.h"
#include "platform/audio/AudioUtilities.h"
#include "wtf/MathExtras.h"
#include <algorithm>
// Use a 50ms smoothing / de-zippering time-constant.
const float SmoothingTimeConstant = 0.050f;
namespace blink {
// Implement equal-power panning algorithm for mono or stereo input.
// See: http://webaudio.github.io/web-audio-api/#panning-algorithm
StereoPanner::StereoPanner(float sampleRate) : Spatializer(PanningModelEqualPower)
, m_isFirstRender(true)
, m_gainL(0.5)
, m_gainR(0.5)
{
m_smoothingConstant = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate);
}
void StereoPanner::panWithSampleAccurateValues(const AudioBus* inputBus, AudioBus* outputBus, const float* panValues, size_t framesToProcess)
{
bool isInputSafe = inputBus
&& (inputBus->numberOfChannels() == 1 || inputBus->numberOfChannels() == 2)
&& framesToProcess <= inputBus->length();
ASSERT(isInputSafe);
if (!isInputSafe)
return;
unsigned numberOfInputChannels = inputBus->numberOfChannels();
bool isOutputSafe = outputBus
&& outputBus->numberOfChannels() == 2
&& framesToProcess <= outputBus->length();
ASSERT(isOutputSafe);
if (!isOutputSafe)
return;
const float* sourceL = inputBus->channel(0)->data();
const float* sourceR = numberOfInputChannels > 1 ? inputBus->channel(1)->data() : sourceL;
float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->mutableData();
float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->mutableData();
if (!sourceL || !sourceR || !destinationL || !destinationR)
return;
// Cache in local variables.
double gainL = m_gainL;
double gainR = m_gainR;
int n = framesToProcess;
if (numberOfInputChannels == 1) { // For mono source case.
while (n--) {
float inputL = *sourceL++;
float panValue = clampTo(*panValues++, -1.0, 1.0);
double panPosition = (panValue * 0.5 + 0.5) * piOverTwoDouble;
gainL = std::cos(panPosition);
gainR = std::sin(panPosition);
*destinationL++ = static_cast<float>(inputL * gainL);
*destinationR++ = static_cast<float>(inputL * gainR);
}
} else { // For stereo source case.
while (n--) {
float inputL = *sourceL++;
float inputR = *sourceR++;
float panValue = clampTo(*panValues++, -1.0, 1.0);
double panPosition = panValue <= 0 ? panValue + 1 : panValue;
panPosition *= piOverTwoDouble;
gainL = std::cos(panPosition);
gainR = std::sin(panPosition);
if (panValue <= 0) {
*destinationL++ = static_cast<float>(inputL + inputR * gainL);
*destinationR++ = static_cast<float>(inputR * gainR);
} else {
*destinationL++ = static_cast<float>(inputL * gainL);
*destinationR++ = static_cast<float>(inputR + inputL * gainR);
}
}
}
m_gainL = gainL;
m_gainR = gainR;
}
void StereoPanner::panToTargetValue(const AudioBus* inputBus, AudioBus* outputBus, float panValue, size_t framesToProcess)
{
bool isInputSafe = inputBus
&& (inputBus->numberOfChannels() == 1 || inputBus->numberOfChannels() == 2)
&& framesToProcess <= inputBus->length();
ASSERT(isInputSafe);
if (!isInputSafe)
return;
unsigned numberOfInputChannels = inputBus->numberOfChannels();
bool isOutputSafe = outputBus
&& outputBus->numberOfChannels() == 2
&& framesToProcess <= outputBus->length();
ASSERT(isOutputSafe);
if (!isOutputSafe)
return;
const float* sourceL = inputBus->channel(0)->data();
const float* sourceR = numberOfInputChannels > 1 ? inputBus->channel(1)->data() : sourceL;
float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->mutableData();
float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->mutableData();
if (!sourceL || !sourceR || !destinationL || !destinationR)
return;
float panValueClamped = clampTo(panValue, -1.0, 1.0);
double panPosition;
// Normalize pan values to [0; 1] based on 1) channel type and the value
// polarity.
if (numberOfInputChannels == 1) { // For mono input source.
// Pan from left to right [-1; 1] will be normalized as [0; 1].
panPosition = panValueClamped * 0.5 + 0.5;
} else { // For stereo input source.
if (panValueClamped <= 0) { // Normalize [-1; 0] to [0; 1].
panPosition = panValueClamped + 1;
} else { // Do nothing when [0; 1].
panPosition = panValueClamped;
}
}
panPosition *= piOverTwoDouble;
double targetGainL = std::cos(panPosition);
double targetGainR = std::sin(panPosition);
// Don't de-zipper on first render call.
if (m_isFirstRender) {
m_isFirstRender = false;
m_gainL = targetGainL;
m_gainR = targetGainR;
}
// 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;
if (numberOfInputChannels == 1) { // For mono source case.
while (n--) {
float inputL = *sourceL++;
gainL += (targetGainL - gainL) * SmoothingConstant;
gainR += (targetGainR - gainR) * SmoothingConstant;
*destinationL++ = static_cast<float>(inputL * gainL);
*destinationR++ = static_cast<float>(inputL * gainR);
}
} else { // For stereo source case.
if (panValueClamped <= 0) {
// When [-1; 0], keep left channel intact and equal-power pan the
// right channel only.
while (n--) {
float inputL = *sourceL++;
float inputR = *sourceR++;
gainL += (targetGainL - gainL) * SmoothingConstant;
gainR += (targetGainR - gainR) * SmoothingConstant;
*destinationL++ = static_cast<float>(inputL + inputR * gainL);
*destinationR++ = static_cast<float>(inputR * gainR);
}
} else {
// When [0; 1], keep right channel intact and equal-power pan the
// left channel only.
while (n--) {
float inputL = *sourceL++;
float inputR = *sourceR++;
gainL += (targetGainL - gainL) * SmoothingConstant;
gainR += (targetGainR - gainR) * SmoothingConstant;
*destinationL++ = static_cast<float>(inputL * gainL);
*destinationR++ = static_cast<float>(inputR + inputL * gainR);
}
}
}
m_gainL = gainL;
m_gainR = gainR;
}
} // namespace blink
#endif // ENABLE(WEB_AUDIO)
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