DelayDSPKernel.cpp [plain text]
#include "config.h"
#if ENABLE(WEB_AUDIO)
#include "DelayDSPKernel.h"
#include "AudioUtilities.h"
#include <algorithm>
using namespace std;
const double DefaultMaxDelayTime = 1.0;
const double SmoothingTimeConstant = 0.020;
namespace WebCore {
DelayDSPKernel::DelayDSPKernel(DelayProcessor* processor)
: AudioDSPKernel(processor)
, m_maxDelayTime(DefaultMaxDelayTime)
, m_writeIndex(0)
, m_firstTime(true)
{
ASSERT(processor && processor->sampleRate() > 0);
if (!processor)
return;
m_buffer.resize(static_cast<size_t>(processor->sampleRate() * DefaultMaxDelayTime));
m_buffer.zero();
m_smoothingRate = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, processor->sampleRate());
}
DelayDSPKernel::DelayDSPKernel(double maxDelayTime, double sampleRate)
: AudioDSPKernel(sampleRate)
, m_maxDelayTime(maxDelayTime)
, m_writeIndex(0)
, m_firstTime(true)
{
ASSERT(maxDelayTime > 0.0);
if (maxDelayTime <= 0.0)
return;
size_t bufferLength = static_cast<size_t>(sampleRate * maxDelayTime);
ASSERT(bufferLength);
if (!bufferLength)
return;
m_buffer.resize(bufferLength);
m_buffer.zero();
m_smoothingRate = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate);
}
void DelayDSPKernel::process(const float* source, float* destination, size_t framesToProcess)
{
size_t bufferLength = m_buffer.size();
float* buffer = m_buffer.data();
ASSERT(bufferLength);
if (!bufferLength)
return;
ASSERT(source && destination);
if (!source || !destination)
return;
double sampleRate = this->sampleRate();
double delayTime = delayProcessor() ? delayProcessor()->delayTime()->value() : m_desiredDelayFrames / sampleRate;
delayTime = min(maxDelayTime(), delayTime);
delayTime = max(0.0, delayTime);
if (m_firstTime) {
m_currentDelayTime = delayTime;
m_firstTime = false;
}
int n = framesToProcess;
while (n--) {
m_currentDelayTime += (delayTime - m_currentDelayTime) * m_smoothingRate;
double desiredDelayFrames = m_currentDelayTime * sampleRate;
double readPosition = m_writeIndex + bufferLength - desiredDelayFrames;
if (readPosition > bufferLength)
readPosition -= bufferLength;
int readIndex1 = static_cast<int>(readPosition);
int readIndex2 = (readIndex1 + 1) % bufferLength;
double interpolationFactor = readPosition - readIndex1;
double input = static_cast<float>(*source++);
buffer[m_writeIndex] = static_cast<float>(input);
m_writeIndex = (m_writeIndex + 1) % bufferLength;
double sample1 = buffer[readIndex1];
double sample2 = buffer[readIndex2];
double output = (1.0 - interpolationFactor) * sample1 + interpolationFactor * sample2;
*destination++ = static_cast<float>(output);
}
}
void DelayDSPKernel::reset()
{
m_firstTime = true;
m_buffer.zero();
}
}
#endif // ENABLE(WEB_AUDIO)