void WaveShaperDSPKernel::processCurve(const float* source, float* destination, size_t framesToProcess)
{
ASSERT(source);
ASSERT(destination);
ASSERT(waveShaperProcessor());
DOMFloat32Array* curve = waveShaperProcessor()->curve();
if (!curve) {
// Act as "straight wire" pass-through if no curve is set.
memcpy(destination, source, sizeof(float) * framesToProcess);
return;
}
float* curveData = curve->data();
int curveLength = curve->length();
ASSERT(curveData);
if (!curveData || !curveLength) {
memcpy(destination, source, sizeof(float) * framesToProcess);
return;
}
// Apply waveshaping curve.
for (unsigned i = 0; i < framesToProcess; ++i) {
const float input = source[i];
// Calculate a virtual index based on input -1 -> +1 with -1 being curve[0], +1 being
// curve[curveLength - 1], and 0 being at the center of the curve data. Then linearly
// interpolate between the two points in the curve.
double virtualIndex = 0.5 * (input + 1) * (curveLength - 1);
double output;
if (virtualIndex < 0) {
// input < -1, so use curve[0]
output = curveData[0];
} else if (virtualIndex >= curveLength - 1) {
// input >= 1, so use last curve value
output = curveData[curveLength - 1];
} else {
// The general case where -1 <= input < 1, where 0 <= virtualIndex < curveLength - 1,
// so interpolate between the nearest samples on the curve.
unsigned index1 = static_cast<unsigned>(virtualIndex);
unsigned index2 = index1 + 1;
double interpolationFactor = virtualIndex - index1;
double value1 = curveData[index1];
double value2 = curveData[index2];
output = (1.0 - interpolationFactor) * value1 + interpolationFactor * value2;
}
destination[i] = output;
}
}
float AudioParamTimeline::valuesForFrameRangeImpl(
size_t startFrame,
size_t endFrame,
float defaultValue,
float* values,
unsigned numberOfValues,
double sampleRate,
double controlRate)
{
ASSERT(values);
if (!values)
return defaultValue;
// Return default value if there are no events matching the desired time range.
if (!m_events.size() || (endFrame / sampleRate <= m_events[0].time())) {
for (unsigned i = 0; i < numberOfValues; ++i)
values[i] = defaultValue;
return defaultValue;
}
// Maintain a running time (frame) and index for writing the values buffer.
size_t currentFrame = startFrame;
unsigned writeIndex = 0;
// If first event is after startFrame then fill initial part of values buffer with defaultValue
// until we reach the first event time.
double firstEventTime = m_events[0].time();
if (firstEventTime > startFrame / sampleRate) {
// |fillToFrame| is an exclusive upper bound, so use ceil() to compute the bound from the
// firstEventTime.
size_t fillToFrame = std::min(endFrame, static_cast<size_t>(ceil(firstEventTime * sampleRate)));
ASSERT(fillToFrame >= startFrame);
fillToFrame -= startFrame;
fillToFrame = std::min(fillToFrame, static_cast<size_t>(numberOfValues));
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = defaultValue;
currentFrame += fillToFrame;
}
float value = defaultValue;
// Go through each event and render the value buffer where the times overlap,
// stopping when we've rendered all the requested values.
// FIXME: could try to optimize by avoiding having to iterate starting from the very first event
// and keeping track of a "current" event index.
int n = m_events.size();
for (int i = 0; i < n && writeIndex < numberOfValues; ++i) {
ParamEvent& event = m_events[i];
ParamEvent* nextEvent = i < n - 1 ? &(m_events[i + 1]) : 0;
// Wait until we get a more recent event.
if (nextEvent && nextEvent->time() < currentFrame / sampleRate) {
// But if the current event is a SetValue event and the event time is between
// currentFrame - 1 and curentFrame (in time). we don't want to skip it. If we do skip
// it, the SetValue event is completely skipped and not applied, which is wrong. Other
// events don't have this problem. (Because currentFrame is unsigned, we do the time
// check in this funny, but equivalent way.)
double eventFrame = event.time() * sampleRate;
// Condition is currentFrame - 1 < eventFrame <= currentFrame, but currentFrame is
// unsigned and could be 0, so use currentFrame < eventFrame + 1 instead.
if (!((event.type() == ParamEvent::SetValue
&& (eventFrame <= currentFrame)
&& (currentFrame < eventFrame + 1))))
continue;
}
float value1 = event.value();
double time1 = event.time();
float value2 = nextEvent ? nextEvent->value() : value1;
double time2 = nextEvent ? nextEvent->time() : endFrame / sampleRate + 1;
double deltaTime = time2 - time1;
float k = deltaTime > 0 ? 1 / deltaTime : 0;
// |fillToEndFrame| is the exclusive upper bound of the last frame to be computed for this
// event. It's either the last desired frame (|endFrame|) or derived from the end time of
// the next event (time2). We compute ceil(time2*sampleRate) because fillToEndFrame is the
// exclusive upper bound. Consider the case where |startFrame| = 128 and time2 = 128.1
// (assuming sampleRate = 1). Since time2 is greater than 128, we want to output a value
// for frame 128. This requires that fillToEndFrame be at least 129. This is achieved by
// ceil(time2).
size_t fillToEndFrame = std::min(endFrame, static_cast<size_t>(ceil(time2 * sampleRate)));
ASSERT(fillToEndFrame >= startFrame);
size_t fillToFrame = fillToEndFrame - startFrame;
fillToFrame = std::min(fillToFrame, static_cast<size_t>(numberOfValues));
ParamEvent::Type nextEventType = nextEvent ? static_cast<ParamEvent::Type>(nextEvent->type()) : ParamEvent::LastType /* unknown */;
// First handle linear and exponential ramps which require looking ahead to the next event.
if (nextEventType == ParamEvent::LinearRampToValue) {
const float valueDelta = value2 - value1;
#if CPU(X86) || CPU(X86_64)
// Minimize in-loop operations. Calculate starting value and increment. Next step: value += inc.
// value = value1 + (currentFrame/sampleRate - time1) * k * (value2 - value1);
// inc = 4 / sampleRate * k * (value2 - value1);
// Resolve recursion by expanding constants to achieve a 4-step loop unrolling.
// value = value1 + ((currentFrame/sampleRate - time1) + i * sampleFrameTimeIncr) * k * (value2 -value1), i in 0..3
__m128 vValue = _mm_mul_ps(_mm_set_ps1(1 / sampleRate), _mm_set_ps(3, 2, 1, 0));
vValue = _mm_add_ps(vValue, _mm_set_ps1(currentFrame / sampleRate - time1));
vValue = _mm_mul_ps(vValue, _mm_set_ps1(k * valueDelta));
vValue = _mm_add_ps(vValue, _mm_set_ps1(value1));
__m128 vInc = _mm_set_ps1(4 / sampleRate * k * valueDelta);
// Truncate loop steps to multiple of 4.
unsigned fillToFrameTrunc = writeIndex + ((fillToFrame - writeIndex) / 4) * 4;
// Compute final time.
currentFrame += fillToFrameTrunc - writeIndex;
// Process 4 loop steps.
for (; writeIndex < fillToFrameTrunc; writeIndex += 4) {
_mm_storeu_ps(values + writeIndex, vValue);
vValue = _mm_add_ps(vValue, vInc);
}
#endif
// Serially process remaining values.
for (; writeIndex < fillToFrame; ++writeIndex) {
float x = (currentFrame / sampleRate - time1) * k;
// value = (1 - x) * value1 + x * value2;
value = value1 + x * valueDelta;
values[writeIndex] = value;
++currentFrame;
}
} else if (nextEventType == ParamEvent::ExponentialRampToValue) {
if (value1 <= 0 || value2 <= 0) {
// Handle negative values error case by propagating previous value.
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = value;
} else {
float numSampleFrames = deltaTime * sampleRate;
// The value goes exponentially from value1 to value2 in a duration of deltaTime
// seconds according to
//
// v(t) = v1*(v2/v1)^((t-t1)/(t2-t1))
//
// Let c be currentFrame and F be the sampleRate. Then we want to sample v(t)
// at times t = (c + k)/F for k = 0, 1, ...:
//
// v((c+k)/F) = v1*(v2/v1)^(((c/F+k/F)-t1)/(t2-t1))
// = v1*(v2/v1)^((c/F-t1)/(t2-t1))
// *(v2/v1)^((k/F)/(t2-t1))
// = v1*(v2/v1)^((c/F-t1)/(t2-t1))
// *[(v2/v1)^(1/(F*(t2-t1)))]^k
//
// Thus, this can be written as
//
// v((c+k)/F) = V*m^k
//
// where
// V = v1*(v2/v1)^((c/F-t1)/(t2-t1))
// m = (v2/v1)^(1/(F*(t2-t1)))
// Compute the per-sample multiplier.
float multiplier = powf(value2 / value1, 1 / numSampleFrames);
// Set the starting value of the exponential ramp.
value = value1 * powf(value2 / value1,
(currentFrame / sampleRate - time1) / deltaTime);
for (; writeIndex < fillToFrame; ++writeIndex) {
values[writeIndex] = value;
value *= multiplier;
++currentFrame;
}
}
} else {
// Handle event types not requiring looking ahead to the next event.
switch (event.type()) {
case ParamEvent::SetValue:
case ParamEvent::LinearRampToValue:
case ParamEvent::ExponentialRampToValue:
{
currentFrame = fillToEndFrame;
// Simply stay at a constant value.
value = event.value();
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = value;
break;
}
case ParamEvent::SetTarget:
{
// Exponential approach to target value with given time constant.
//
// v(t) = v2 + (v1 - v2)*exp(-(t-t1/tau))
//
float target = event.value();
float timeConstant = event.timeConstant();
float discreteTimeConstant = static_cast<float>(AudioUtilities::discreteTimeConstantForSampleRate(timeConstant, controlRate));
// Set the starting value correctly. This is only needed when the current time
// is "equal" to the start time of this event. This is to get the sampling
// correct if the start time of this automation isn't on a frame boundary.
// Otherwise, we can just continue from where we left off from the previous
// rendering quantum.
{
double rampStartFrame = time1 * sampleRate;
// Condition is c - 1 < r <= c where c = currentFrame and r =
// rampStartFrame. Compute it this way because currentFrame is unsigned and
// could be 0.
if (rampStartFrame <= currentFrame && currentFrame < rampStartFrame + 1)
value = target + (value - target) * exp(-(currentFrame / sampleRate - time1) / timeConstant);
}
#if CPU(X86) || CPU(X86_64)
// Resolve recursion by expanding constants to achieve a 4-step loop unrolling.
// v1 = v0 + (t - v0) * c
// v2 = v1 + (t - v1) * c
// v2 = v0 + (t - v0) * c + (t - (v0 + (t - v0) * c)) * c
// v2 = v0 + (t - v0) * c + (t - v0) * c - (t - v0) * c * c
// v2 = v0 + (t - v0) * c * (2 - c)
// Thus c0 = c, c1 = c*(2-c). The same logic applies to c2 and c3.
const float c0 = discreteTimeConstant;
const float c1 = c0 * (2 - c0);
const float c2 = c0 * ((c0 - 3) * c0 + 3);
const float c3 = c0 * (c0 * ((4 - c0) * c0 - 6) + 4);
float delta;
__m128 vC = _mm_set_ps(c2, c1, c0, 0);
__m128 vDelta, vValue, vResult;
// Process 4 loop steps.
unsigned fillToFrameTrunc = writeIndex + ((fillToFrame - writeIndex) / 4) * 4;
for (; writeIndex < fillToFrameTrunc; writeIndex += 4) {
delta = target - value;
vDelta = _mm_set_ps1(delta);
vValue = _mm_set_ps1(value);
vResult = _mm_add_ps(vValue, _mm_mul_ps(vDelta, vC));
_mm_storeu_ps(values + writeIndex, vResult);
// Update value for next iteration.
value += delta * c3;
}
#endif
// Serially process remaining values
for (; writeIndex < fillToFrame; ++writeIndex) {
values[writeIndex] = value;
value += (target - value) * discreteTimeConstant;
}
currentFrame = fillToEndFrame;
break;
}
case ParamEvent::SetValueCurve:
{
DOMFloat32Array* curve = event.curve();
float* curveData = curve ? curve->data() : 0;
unsigned numberOfCurvePoints = curve ? curve->length() : 0;
// Curve events have duration, so don't just use next event time.
double duration = event.duration();
double durationFrames = duration * sampleRate;
// How much to step the curve index for each frame. We want the curve index to
// be exactly equal to the last index (numberOfCurvePoints - 1) after
// durationFrames - 1 frames. In this way, the last output value will equal the
// last value in the curve array.
double curvePointsPerFrame;
// If the duration is less than a frame, we want to just output the last curve
// value. Do this by setting curvePointsPerFrame to be more than number of
// points in the curve. Then the curveVirtualIndex will always exceed the last
// curve index, so that the last curve value will be used.
if (durationFrames > 1)
curvePointsPerFrame = (numberOfCurvePoints - 1) / (durationFrames - 1);
else
curvePointsPerFrame = numberOfCurvePoints + 1;
if (!curve || !curveData || !numberOfCurvePoints || duration <= 0 || sampleRate <= 0) {
// Error condition - simply propagate previous value.
currentFrame = fillToEndFrame;
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = value;
break;
}
// Save old values and recalculate information based on the curve's duration
// instead of the next event time.
size_t nextEventFillToFrame = fillToFrame;
// Use ceil here for the same reason as using ceil above: fillToEndFrame is an
// exclusive upper bound of the last frame to be computed.
fillToEndFrame = std::min(endFrame, static_cast<size_t>(ceil(sampleRate*(time1 + duration))));
// |fillToFrame| can be less than |startFrame| when the end of the
// setValueCurve automation has been reached, but the next automation has not
// yet started. In this case, |fillToFrame| is clipped to |time1|+|duration|
// above, but |startFrame| will keep increasing (because the current time is
// increasing).
fillToFrame = (fillToEndFrame < startFrame) ? 0 : fillToEndFrame - startFrame;
fillToFrame = std::min(fillToFrame, static_cast<size_t>(numberOfValues));
// Index into the curve data using a floating-point value.
// We're scaling the number of curve points by the duration (see curvePointsPerFrame).
double curveVirtualIndex = 0;
if (time1 < currentFrame / sampleRate) {
// Index somewhere in the middle of the curve data.
// Don't use timeToSampleFrame() since we want the exact floating-point frame.
double frameOffset = currentFrame - time1 * sampleRate;
curveVirtualIndex = curvePointsPerFrame * frameOffset;
}
// Set the default value in case fillToFrame is 0.
value = curveData[numberOfCurvePoints - 1];
// Render the stretched curve data using linear interpolation. Oversampled
// curve data can be provided if sharp discontinuities are desired.
unsigned k = 0;
#if CPU(X86) || CPU(X86_64)
const __m128 vCurveVirtualIndex = _mm_set_ps1(curveVirtualIndex);
const __m128 vCurvePointsPerFrame = _mm_set_ps1(curvePointsPerFrame);
const __m128 vNumberOfCurvePointsM1 = _mm_set_ps1(numberOfCurvePoints - 1);
const __m128 vN1 = _mm_set_ps1(1.0f);
const __m128 vN4 = _mm_set_ps1(4.0f);
__m128 vK = _mm_set_ps(3, 2, 1, 0);
int aCurveIndex0[4];
int aCurveIndex1[4];
// Truncate loop steps to multiple of 4
unsigned truncatedSteps = ((fillToFrame - writeIndex) / 4) * 4;
unsigned fillToFrameTrunc = writeIndex + truncatedSteps;
for (; writeIndex < fillToFrameTrunc; writeIndex += 4) {
// Compute current index this way to minimize round-off that would have
// occurred by incrementing the index by curvePointsPerFrame.
__m128 vCurrentVirtualIndex = _mm_add_ps(vCurveVirtualIndex, _mm_mul_ps(vK, vCurvePointsPerFrame));
vK = _mm_add_ps(vK, vN4);
// Clamp index to the last element of the array.
__m128i vCurveIndex0 = _mm_cvttps_epi32(_mm_min_ps(vCurrentVirtualIndex, vNumberOfCurvePointsM1));
__m128i vCurveIndex1 = _mm_cvttps_epi32(_mm_min_ps(_mm_add_ps(vCurrentVirtualIndex, vN1), vNumberOfCurvePointsM1));
// Linearly interpolate between the two nearest curve points. |delta| is
// clamped to 1 because currentVirtualIndex can exceed curveIndex0 by more
// than one. This can happen when we reached the end of the curve but still
// need values to fill out the current rendering quantum.
_mm_storeu_si128((__m128i*)aCurveIndex0, vCurveIndex0);
_mm_storeu_si128((__m128i*)aCurveIndex1, vCurveIndex1);
__m128 vC0 = _mm_set_ps(curveData[aCurveIndex0[3]], curveData[aCurveIndex0[2]], curveData[aCurveIndex0[1]], curveData[aCurveIndex0[0]]);
__m128 vC1 = _mm_set_ps(curveData[aCurveIndex1[3]], curveData[aCurveIndex1[2]], curveData[aCurveIndex1[1]], curveData[aCurveIndex1[0]]);
__m128 vDelta = _mm_min_ps(_mm_sub_ps(vCurrentVirtualIndex, _mm_cvtepi32_ps(vCurveIndex0)), vN1);
__m128 vValue = _mm_add_ps(vC0, _mm_mul_ps(_mm_sub_ps(vC1, vC0), vDelta));
_mm_storeu_ps(values + writeIndex, vValue);
}
// Pass along k to the serial loop.
k = truncatedSteps;
// If the above loop was run, pass along the last computed value.
if (truncatedSteps > 0) {
value = values[writeIndex - 1];
}
#endif
for (; writeIndex < fillToFrame; ++writeIndex, ++k) {
// Compute current index this way to minimize round-off that would have
// occurred by incrementing the index by curvePointsPerFrame.
double currentVirtualIndex = curveVirtualIndex + k * curvePointsPerFrame;
unsigned curveIndex0;
// Clamp index to the last element of the array.
if (currentVirtualIndex < numberOfCurvePoints) {
curveIndex0 = static_cast<unsigned>(currentVirtualIndex);
} else {
curveIndex0 = numberOfCurvePoints - 1;
}
unsigned curveIndex1 = std::min(curveIndex0 + 1, numberOfCurvePoints - 1);
// Linearly interpolate between the two nearest curve points. |delta| is
// clamped to 1 because currentVirtualIndex can exceed curveIndex0 by more
// than one. This can happen when we reached the end of the curve but still
// need values to fill out the current rendering quantum.
ASSERT(curveIndex0 < numberOfCurvePoints);
ASSERT(curveIndex1 < numberOfCurvePoints);
float c0 = curveData[curveIndex0];
float c1 = curveData[curveIndex1];
double delta = std::min(currentVirtualIndex - curveIndex0, 1.0);
value = c0 + (c1 - c0) * delta;
values[writeIndex] = value;
}
// If there's any time left after the duration of this event and the start
// of the next, then just propagate the last value of the curveData.
value = curveData[numberOfCurvePoints - 1];
for (; writeIndex < nextEventFillToFrame; ++writeIndex)
values[writeIndex] = value;
// Re-adjust current time
currentFrame = nextEventFillToFrame;
break;
}
case ParamEvent::LastType:
ASSERT_NOT_REACHED();
break;
}
}
}
// If there's any time left after processing the last event then just propagate the last value
// to the end of the values buffer.
for (; writeIndex < numberOfValues; ++writeIndex)
values[writeIndex] = value;
return value;
}
float AudioParamTimeline::valuesForTimeRangeImpl(
double startTime,
double endTime,
float defaultValue,
float* values,
unsigned numberOfValues,
double sampleRate,
double controlRate)
{
ASSERT(values);
if (!values)
return defaultValue;
// Return default value if there are no events matching the desired time range.
if (!m_events.size() || endTime <= m_events[0].time()) {
for (unsigned i = 0; i < numberOfValues; ++i)
values[i] = defaultValue;
return defaultValue;
}
// Maintain a running time and index for writing the values buffer.
double currentTime = startTime;
unsigned writeIndex = 0;
// If first event is after startTime then fill initial part of values buffer with defaultValue
// until we reach the first event time.
double firstEventTime = m_events[0].time();
if (firstEventTime > startTime) {
double fillToTime = std::min(endTime, firstEventTime);
unsigned fillToFrame = AudioUtilities::timeToSampleFrame(fillToTime - startTime, sampleRate);
fillToFrame = std::min(fillToFrame, numberOfValues);
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = defaultValue;
currentTime = fillToTime;
}
float value = defaultValue;
// Go through each event and render the value buffer where the times overlap,
// stopping when we've rendered all the requested values.
// FIXME: could try to optimize by avoiding having to iterate starting from the very first event
// and keeping track of a "current" event index.
int n = m_events.size();
for (int i = 0; i < n && writeIndex < numberOfValues; ++i) {
ParamEvent& event = m_events[i];
ParamEvent* nextEvent = i < n - 1 ? &(m_events[i + 1]) : 0;
// Wait until we get a more recent event.
if (nextEvent && nextEvent->time() < currentTime)
continue;
float value1 = event.value();
double time1 = event.time();
float value2 = nextEvent ? nextEvent->value() : value1;
double time2 = nextEvent ? nextEvent->time() : endTime + 1;
double deltaTime = time2 - time1;
float k = deltaTime > 0 ? 1 / deltaTime : 0;
double sampleFrameTimeIncr = 1 / sampleRate;
double fillToTime = std::min(endTime, time2);
unsigned fillToFrame = AudioUtilities::timeToSampleFrame(fillToTime - startTime, sampleRate);
fillToFrame = std::min(fillToFrame, numberOfValues);
ParamEvent::Type nextEventType = nextEvent ? static_cast<ParamEvent::Type>(nextEvent->type()) : ParamEvent::LastType /* unknown */;
// First handle linear and exponential ramps which require looking ahead to the next event.
if (nextEventType == ParamEvent::LinearRampToValue) {
for (; writeIndex < fillToFrame; ++writeIndex) {
float x = (currentTime - time1) * k;
value = (1 - x) * value1 + x * value2;
values[writeIndex] = value;
currentTime += sampleFrameTimeIncr;
}
} else if (nextEventType == ParamEvent::ExponentialRampToValue) {
if (value1 <= 0 || value2 <= 0) {
// Handle negative values error case by propagating previous value.
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = value;
} else {
float numSampleFrames = deltaTime * sampleRate;
// The value goes exponentially from value1 to value2 in a duration of deltaTime seconds (corresponding to numSampleFrames).
// Compute the per-sample multiplier.
float multiplier = powf(value2 / value1, 1 / numSampleFrames);
// Set the starting value of the exponential ramp. This is the same as multiplier ^
// AudioUtilities::timeToSampleFrame(currentTime - time1, sampleRate), but is more
// accurate, especially if multiplier is close to 1.
value = value1 * powf(value2 / value1,
AudioUtilities::timeToSampleFrame(currentTime - time1, sampleRate) / numSampleFrames);
for (; writeIndex < fillToFrame; ++writeIndex) {
values[writeIndex] = value;
value *= multiplier;
currentTime += sampleFrameTimeIncr;
}
}
} else {
// Handle event types not requiring looking ahead to the next event.
switch (event.type()) {
case ParamEvent::SetValue:
case ParamEvent::LinearRampToValue:
case ParamEvent::ExponentialRampToValue:
{
currentTime = fillToTime;
// Simply stay at a constant value.
value = event.value();
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = value;
break;
}
case ParamEvent::SetTarget:
{
currentTime = fillToTime;
// Exponential approach to target value with given time constant.
float target = event.value();
float timeConstant = event.timeConstant();
float discreteTimeConstant = static_cast<float>(AudioUtilities::discreteTimeConstantForSampleRate(timeConstant, controlRate));
for (; writeIndex < fillToFrame; ++writeIndex) {
values[writeIndex] = value;
value += (target - value) * discreteTimeConstant;
}
break;
}
case ParamEvent::SetValueCurve:
{
DOMFloat32Array* curve = event.curve();
float* curveData = curve ? curve->data() : 0;
unsigned numberOfCurvePoints = curve ? curve->length() : 0;
// Curve events have duration, so don't just use next event time.
float duration = event.duration();
float durationFrames = duration * sampleRate;
float curvePointsPerFrame = static_cast<float>(numberOfCurvePoints) / durationFrames;
if (!curve || !curveData || !numberOfCurvePoints || duration <= 0 || sampleRate <= 0) {
// Error condition - simply propagate previous value.
currentTime = fillToTime;
for (; writeIndex < fillToFrame; ++writeIndex)
values[writeIndex] = value;
break;
}
// Save old values and recalculate information based on the curve's duration
// instead of the next event time.
unsigned nextEventFillToFrame = fillToFrame;
float nextEventFillToTime = fillToTime;
fillToTime = std::min(endTime, time1 + duration);
fillToFrame = AudioUtilities::timeToSampleFrame(fillToTime - startTime, sampleRate);
fillToFrame = std::min(fillToFrame, numberOfValues);
// Index into the curve data using a floating-point value.
// We're scaling the number of curve points by the duration (see curvePointsPerFrame).
float curveVirtualIndex = 0;
if (time1 < currentTime) {
// Index somewhere in the middle of the curve data.
// Don't use timeToSampleFrame() since we want the exact floating-point frame.
float frameOffset = (currentTime - time1) * sampleRate;
curveVirtualIndex = curvePointsPerFrame * frameOffset;
}
// Render the stretched curve data using nearest neighbor sampling.
// Oversampled curve data can be provided if smoothness is desired.
for (; writeIndex < fillToFrame; ++writeIndex) {
// Ideally we'd use round() from MathExtras, but we're in a tight loop here
// and we're trading off precision for extra speed.
unsigned curveIndex = static_cast<unsigned>(0.5 + curveVirtualIndex);
curveVirtualIndex += curvePointsPerFrame;
// Bounds check.
if (curveIndex < numberOfCurvePoints)
value = curveData[curveIndex];
values[writeIndex] = value;
}
// If there's any time left after the duration of this event and the start
// of the next, then just propagate the last value.
for (; writeIndex < nextEventFillToFrame; ++writeIndex)
values[writeIndex] = value;
// Re-adjust current time
currentTime = nextEventFillToTime;
break;
}
}
}
}
// If there's any time left after processing the last event then just propagate the last value
// to the end of the values buffer.
for (; writeIndex < numberOfValues; ++writeIndex)
values[writeIndex] = value;
return value;
}