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spectrogram: Speed up getLine by removing mod operator

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Mike Walters
2016-06-04 12:45:55 +01:00
parent e38703c4ae
commit 083c8ad486
1 changed files with 3 additions and 1 deletions
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4
spectrogramplot.cpp
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@@ -144,7 +144,9 @@ void SpectrogramPlot::getLine(float *dest, off_t sample)
fft->process(buffer.get(), buffer.get());
for (int i = 0; i < fftSize; i++) {
int k = (i + fftSize / 2) % fftSize;
// Start from the middle of the FFTW array and wrap
// to rearrange the data
int k = (i + fftSize / 2) & (fftSize - 1);
float re = buffer[k].real();
float im = buffer[k].imag();
float mag = sqrt(re * re + im * im) / fftSize;