// _______________________________________________________
void KeyWordDetector::generateWindowFunction() {
computeWindow(window, WINDOW_LENGTH, FFT_WIN_TYP_HAMMING);
// Compute window normalisation factors (weighing factors)
for (int i = 0; i < WINDOW_LENGTH/2; i++){
windowNormS1 += window[i];
windowNormS2 += pow(window[i], 2);
}
// Multiply by two because we only store half of the window
windowNormS1 *= 2;
windowNormS2 *= 2;
// Power spectrum scale is for perfomance resons calculated only once
powerSpectrumScale = 1.0f;
//powerSpectrumScale = 2/(pow(windowNormS1, 2));
#ifdef DEBUG_KD_WINDOW
Serial.println("Window:");
printV(window, WINDOW_LENGTH/2, true);
Serial.print("Window normalisation: S1: ");
Serial.print(windowNormS1);
Serial.print(", S2: ");
Serial.println(windowNormS2);
Serial.print("PowerSpectrumScale: ");
Serial.println(powerSpectrumScale);
#endif
}
Error_t CFft::init( int iBlockLength, int iZeroPadFactor, WindowFunction_t eWindow /*= kWindowHann*/, Windowing_t eWindowing /*= kPreWindow*/ )
{
Error_t rErr = kNoError;
// sanity check
if (!CUtil::isPowOf2(iBlockLength) || iZeroPadFactor <= 0 || !CUtil::isPowOf2(iBlockLength*iZeroPadFactor))
return kFunctionInvalidArgsError;
// clean up
reset();
m_iDataLength = iBlockLength;
m_iFftLength = iBlockLength * iZeroPadFactor;
m_ePrePostWindowOpt = eWindowing;
rErr = allocMemory ();
if (rErr)
return rErr;
rErr = computeWindow (eWindow);
m_bIsInitialized = true;
return rErr;
}
