bool
AnalyserNode::FFTAnalysis()
{
float* inputBuffer;
AlignedFallibleTArray<float> tmpBuffer;
if (mWriteIndex == 0) {
inputBuffer = mBuffer.Elements();
} else {
if (!tmpBuffer.SetLength(FftSize())) {
return false;
}
inputBuffer = tmpBuffer.Elements();
memcpy(inputBuffer, mBuffer.Elements() + mWriteIndex, sizeof(float) * (FftSize() - mWriteIndex));
memcpy(inputBuffer + FftSize() - mWriteIndex, mBuffer.Elements(), sizeof(float) * mWriteIndex);
}
ApplyBlackmanWindow(inputBuffer, FftSize());
mAnalysisBlock.PerformFFT(inputBuffer);
// Normalize so than an input sine wave at 0dBfs registers as 0dBfs (undo FFT scaling factor).
const double magnitudeScale = 1.0 / FftSize();
for (uint32_t i = 0; i < mOutputBuffer.Length(); ++i) {
double scalarMagnitude = NS_hypot(mAnalysisBlock.RealData(i),
mAnalysisBlock.ImagData(i)) *
magnitudeScale;
mOutputBuffer[i] = mSmoothingTimeConstant * mOutputBuffer[i] +
(1.0 - mSmoothingTimeConstant) * scalarMagnitude;
}
return true;
}
bool
AnalyserNode::AllocateBuffer()
{
bool result = true;
if (mBuffer.Length() != FftSize()) {
if (!mBuffer.SetLength(FftSize())) {
return false;
}
memset(mBuffer.Elements(), 0, sizeof(float) * FftSize());
mWriteIndex = 0;
if (!mOutputBuffer.SetLength(FrequencyBinCount())) {
return false;
}
memset(mOutputBuffer.Elements(), 0, sizeof(float) * FrequencyBinCount());
}
return result;
}
void
AnalyserNode::SetFftSize(uint32_t aValue, ErrorResult& aRv)
{
// Disallow values that are not a power of 2 and outside the [32,2048] range
if (aValue < 32 ||
aValue > 2048 ||
(aValue & (aValue - 1)) != 0) {
aRv.Throw(NS_ERROR_DOM_INDEX_SIZE_ERR);
return;
}
if (FftSize() != aValue) {
mAnalysisBlock.SetFFTSize(aValue);
AllocateBuffer();
}
}
