anonymous_namespace{WaveClip.cpp} Namespace Reference

Functions
void	findCorrection (const std::vector< sampleCount > &oldWhere, size_t oldLen, size_t newLen, double t0, double rate, double samplesPerPixel, int &oldX0, double &correction)
void	fillWhere (std::vector< sampleCount > &where, size_t len, double bias, double correction, double t0, double rate, double samplesPerPixel)
void	ComputeSpectrogramGainFactors (size_t fftLen, double rate, int frequencyGain, std::vector< float > &gainFactors)

Function Documentation

ComputeSpectrogramGainFactors()

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

Definition at line 523 of file WaveClip.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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fillWhere()

void anonymous_namespace{WaveClip.cpp}::fillWhere ( std::vector< sampleCount > &  where, size_t  len, double  bias, double  correction, double  t0, double  rate, double  samplesPerPixel  )

inline

Definition at line 297 of file WaveClip.cpp.

{
   // Be careful to make the first value non-negative
   const double w0 = 0.5 + correction + bias + t0 * rate;
   where[0] = sampleCount( std::max(0.0, floor(w0)) );
   for (decltype(len) x = 1; x < len + 1; x++)
      where[x] = sampleCount( floor(w0 + double(x) * samplesPerPixel) );
}

Referenced by WaveClip::GetSpectrogram(), and WaveClip::GetWaveDisplay().

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findCorrection()

void anonymous_namespace{WaveClip.cpp}::findCorrection ( const std::vector< sampleCount > &  oldWhere, size_t  oldLen, size_t  newLen, double  t0, double  rate, double  samplesPerPixel, int &  oldX0, double &  correction  )

inline

Definition at line 253 of file WaveClip.cpp.

{
   // Mitigate the accumulation of location errors
   // in copies of copies of ... of caches.
   // Look at the loop that populates "where" below to understand this.
 
   // Find the sample position that is the origin in the old cache.
   const double oldWhere0 = oldWhere[1].as_double() - samplesPerPixel;
   const double oldWhereLast = oldWhere0 + oldLen * samplesPerPixel;
   // Find the length in samples of the old cache.
   const double denom = oldWhereLast - oldWhere0;
 
   // What sample would go in where[0] with no correction?
   const double guessWhere0 = t0 * rate;
 
   if ( // Skip if old and NEW are disjoint:
      oldWhereLast <= guessWhere0 ||
      guessWhere0 + newLen * samplesPerPixel <= oldWhere0 ||
      // Skip unless denom rounds off to at least 1.
      denom < 0.5)
   {
      // The computation of oldX0 in the other branch
      // may underflow and the assertion would be violated.
      oldX0 =  oldLen;
      correction = 0.0;
   }
   else
   {
      // What integer position in the old cache array does that map to?
      // (even if it is out of bounds)
      oldX0 = floor(0.5 + oldLen * (guessWhere0 - oldWhere0) / denom);
      // What sample count would the old cache have put there?
      const double where0 = oldWhere0 + double(oldX0) * samplesPerPixel;
      // What correction is needed to align the NEW cache with the old?
      const double correction0 = where0 - guessWhere0;
      correction = std::max(-samplesPerPixel, std::min(samplesPerPixel, correction0));
      wxASSERT(correction == correction0);
   }
}

References min().

Referenced by WaveClip::GetSpectrogram(), and WaveClip::GetWaveDisplay().

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