anonymous_namespace{SpectrumCache.cpp} Namespace Reference

Functions
static void	ComputeSpectrumUsingRealFFTf (float *__restrict buffer, const FFTParam *hFFT, const float *__restrict window, size_t len, float *__restrict out)
void	ComputeSpectrogramGainFactors (size_t fftLen, double rate, int frequencyGain, std::vector< float > &gainFactors)

Function Documentation

ComputeSpectrogramGainFactors()

void anonymous_namespace{SpectrumCache.cpp}::ComputeSpectrogramGainFactors	(	size_t	fftLen,
		double	rate,
		int	frequencyGain,
		std::vector< float > &	gainFactors
	)

Definition at line 53 of file SpectrumCache.cpp.

{
   if (frequencyGain > 0) {
      // Compute a frequency-dependent gain factor
      // scaled such that 1000 Hz gets a gain of 0dB
 
      // This is the reciprocal of the bin number of 1000 Hz:
      const double factor = ((double)rate / (double)fftLen) / 1000.0;
 
      auto half = fftLen / 2;
      gainFactors.reserve(half);
      // Don't take logarithm of zero!  Let bin 0 replicate the gain factor for bin 1.
      gainFactors.push_back(frequencyGain*log10(factor));
      for (decltype(half) x = 1; x < half; x++) {
         gainFactors.push_back(frequencyGain*log10(factor * x));
      }
   }
}

Referenced by SpecCache::Populate().

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ComputeSpectrumUsingRealFFTf()

static void anonymous_namespace{SpectrumCache.cpp}::ComputeSpectrumUsingRealFFTf ( float *__restrict  buffer, const FFTParam *  hFFT, const float *__restrict  window, size_t  len, float *__restrict  out  )

static

Definition at line 24 of file SpectrumCache.cpp.

{
   size_t i;
   if(len > hFFT->Points * 2)
      len = hFFT->Points * 2;
   for(i = 0; i < len; i++)
      buffer[i] *= window[i];
   for( ; i < (hFFT->Points * 2); i++)
      buffer[i] = 0; // zero pad as needed
   RealFFTf(buffer, hFFT);
   // Handle the (real-only) DC
   float power = buffer[0] * buffer[0];
   if(power <= 0)
      out[0] = -160.0;
   else
      out[0] = 10.0 * log10f(power);
   for(i = 1; i < hFFT->Points; i++) {
      const int index = hFFT->BitReversed[i];
      const float re = buffer[index], im = buffer[index + 1];
      power = re * re + im * im;
      if(power <= 0)
         out[i] = -160.0;
      else
         out[i] = 10.0*log10f(power);
   }
}

References FFTParam::BitReversed, FFTParam::Points, fast_float::detail::power(), and RealFFTf().

Referenced by SpecCache::CalculateOneSpectrum().

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