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Bug 865256 - Part 3b: Add a complex->real ifft to FFTBlock. r=ehsan

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From ea43bceaf8f6dd2c44d7f55a45f770be19b335a5 Mon Sep 17 00:00:00 2001
Currently FFTBlock only holds the complex frequency domain data
internally, reading and writing to external time domain data
buffers. For PeriodicWave we need to create a real, time domain
signal from real and imaginary frequency domain data. This method
does this without touching the internal output buffer at all.
FFTBlock is just used as a wrapper for kiss_fft_cfg.
This commit is contained in:
Ralph Giles 2013-09-10 11:00:17 -07:00
parent 0713177406
commit 3006203577
1 changed files with 24 additions and 0 deletions
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24
content/media/webaudio/FFTBlock.h
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@ -39,11 +39,14 @@ public:
CreateInterpolatedBlock(const FFTBlock& block0,
const FFTBlock& block1, double interp);
// Transform FFTSize() points of aData and store the result internally.
void PerformFFT(const float* aData)
{
EnsureFFT();
kiss_fftr(mFFT, aData, mOutputBuffer.Elements());
}
// Inverse-transform internal data and store the resulting FFTSize()
// points in aData.
void PerformInverseFFT(float* aData)
{
EnsureIFFT();
@ -52,6 +55,27 @@ public:
aData[i] /= mFFTSize;
}
}
// Inverse-transform the FFTSize()/2+1 points of data in each
// of aRealDataIn and aImagDataIn and store the resulting
// FFTSize() points in aRealDataOut.
void PerformInverseFFT(float* aRealDataIn,
float *aImagDataIn,
float *aRealDataOut)
{
EnsureIFFT();
const uint32_t inputSize = mFFTSize / 2 + 1;
nsTArray<kiss_fft_cpx> inputBuffer;
inputBuffer.SetLength(inputSize);
for (uint32_t i = 0; i < inputSize; ++i) {
inputBuffer[i].r = aRealDataIn[i];
inputBuffer[i].i = aImagDataIn[i];
}
kiss_fftri(mIFFT, inputBuffer.Elements(), aRealDataOut);
for (uint32_t i = 0; i < mFFTSize; ++i) {
aRealDataOut[i] /= mFFTSize;
}
}
void Multiply(const FFTBlock& aFrame)
{
BufferComplexMultiply(reinterpret_cast<const float*>(mOutputBuffer.Elements()),