SpectrogramSettings.cpp

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/**********************************************************************
 
Audacity: A Digital Audio Editor
 
SpectrogramSettings.cpp
 
Paul Licameli
 
*******************************************************************//*******************************************************************/
 
 
#include "SpectrogramSettings.h"
 
#include "AColor.h"
#include "NumberScale.h"
 
#include <algorithm>
 
#include "FFT.h"
#include "Prefs.h"
#include "WaveTrack.h"
 
#include <cmath>
 
#include "AudacityMessageBox.h"
 
IntSetting SpectrumMaxFreq{
   L"/Spectrum/MaxFreq", 20000 };
 
namespace {
// Other settings not yet used outside of this file
 
// To do: migrate these to ChoiceSetting preferences, which will store an
// Identifier instead of a number in the preference file.
IntSetting SpectrumAlgorithm{
   L"/Spectrum/Algorithm", 0 }; // Default to Frequencies
IntSetting SpectrumScale{
   L"/Spectrum/ScaleType", 2 }; // Default to Mel
IntSetting SpectrumWindowFunction{
   L"/Spectrum/WindowType", eWinFuncHann };
 
BoolSetting SpectrumEnableSelection{
   L"/Spectrum/EnableSpectralSelection", true };
IntSetting SpectrumFFTSize{
   L"/Spectrum/FFTSize", 2048 };
IntSetting SpectrumFrequencyGain{
   L"/Spectrum/FrequencyGain", 0 };
IntSetting SpectrumGain{
   L"/Spectrum/Gain", 20 };
BoolSetting SpectrumGrayscale{
   L"/Spectrum/Grayscale", false };
IntSetting SpectrumMinFreq{
   L"/Spectrum/MinFreq", 0 };
IntSetting SpectrumRange{
   L"/Spectrum/Range", 80 };
IntSetting SpectrumZeroPaddingFactor{
   L"/Spectrum/ZeroPaddingFactor", 2 };
 
#ifdef EXPERIMENTAL_FIND_NOTES
BoolSetting SpectrumFindNotes{
   L"/Spectrum/FFTFindNotes", false };
DoubleSetting SpectrumFindNotesMinA{
   L"/Spectrum/FindNotesMinA", -30.0 };
IntSetting SpectrumFindNotesN{
   L"/Spectrum/FindNotesN", 5 };
BoolSetting SpectrumFindNotesQuantize{
   L"/Spectrum/FindNotesQuantize", false };
#endif //EXPERIMENTAL_FIND_NOTES
 
#ifdef EXPERIMENTAL_FFT_Y_GRID
BoolSetting SpectrumYGrid{
   L"/Spectrum/FFTYGrid", false};
#endif
}
 
SpectrogramSettings::Globals::Globals()
{
   LoadPrefs();
}
 
void SpectrogramSettings::Globals::SavePrefs()
{
#ifdef SPECTRAL_SELECTION_GLOBAL_SWITCH
   SpectrumEnableSelection.Write(spectralSelection);
#endif
}
 
void SpectrogramSettings::Globals::LoadPrefs()
{
#ifdef SPECTRAL_SELECTION_GLOBAL_SWITCH
   spectralSelection = SpectrumEnableSelection.Read();
#endif
}
 
SpectrogramSettings::Globals
&SpectrogramSettings::Globals::Get()
{
   static Globals instance;
   return instance;
}
 
static const ChannelGroup::Attachments::RegisteredFactory
key1{ [](auto &) { return nullptr; } };
 
SpectrogramSettings &SpectrogramSettings::Get(const WaveTrack &track)
{
   auto &mutTrack = const_cast<WaveTrack&>(track);
   auto pSettings = mutTrack.Attachments::Find<SpectrogramSettings>(key1);
   if (pSettings)
      return *pSettings;
   else
      return SpectrogramSettings::defaults();
}
 
SpectrogramSettings &SpectrogramSettings::Get(const WaveChannel &channel)
{
   return Get(channel.GetTrack());
}
 
SpectrogramSettings &SpectrogramSettings::Own(WaveChannel &wc)
{
   auto &track = wc.GetTrack();
   auto pSettings = track.Attachments::Find<SpectrogramSettings>(key1);
   if (!pSettings) {
      auto uSettings = std::make_unique<SpectrogramSettings>();
      pSettings = uSettings.get();
      track.Attachments::Assign(key1, std::move(uSettings));
   }
   return *pSettings;
}
 
void SpectrogramSettings::Reset(WaveChannel &wc)
{
   wc.GetTrack().Attachments::Assign(key1, nullptr);
}
 
SpectrogramSettings::SpectrogramSettings()
{
   LoadPrefs();
}
 
SpectrogramSettings::SpectrogramSettings(const SpectrogramSettings &other)
   : minFreq(other.minFreq)
   , maxFreq(other.maxFreq)
   , range(other.range)
   , gain(other.gain)
   , frequencyGain(other.frequencyGain)
   , windowType(other.windowType)
   , windowSize(other.windowSize)
   , zeroPaddingFactor(other.zeroPaddingFactor)
   , colorScheme(other.colorScheme)
   , scaleType(other.scaleType)
#ifndef SPECTRAL_SELECTION_GLOBAL_SWITCH
   , spectralSelection(other.spectralSelection)
#endif
   , algorithm(other.algorithm)
#ifdef EXPERIMENTAL_FFT_Y_GRID
   , fftYGrid(other.fftYGrid)
#endif
#ifdef EXPERIMENTAL_FIND_NOTES
   , fftFindNotes(other.fftFindNotes)
   , findNotesMinA(other.findNotesMinA)
   , numberOfMaxima(other.numberOfMaxima)
   , findNotesQuantize(other.findNotesQuantize)
#endif
 
   // Do not copy these!
   , hFFT{}
   , window{}
   , tWindow{}
   , dWindow{}
{
}
 
SpectrogramSettings &SpectrogramSettings::operator= (const SpectrogramSettings &other)
{
   if (this != &other) {
      minFreq = other.minFreq;
      maxFreq = other.maxFreq;
      range = other.range;
      gain = other.gain;
      frequencyGain = other.frequencyGain;
      windowType = other.windowType;
      windowSize = other.windowSize;
      zeroPaddingFactor = other.zeroPaddingFactor;
      colorScheme = other.colorScheme;
      scaleType = other.scaleType;
#ifndef SPECTRAL_SELECTION_GLOBAL_SWITCH
      spectralSelection = other.spectralSelection;
#endif
      algorithm = other.algorithm;
#ifdef EXPERIMENTAL_FFT_Y_GRID
      fftYGrid = other.fftYGrid;
#endif
#ifdef EXPERIMENTAL_FIND_NOTES
      fftFindNotes = other.fftFindNotes;
      findNotesMinA = other.findNotesMinA;
      numberOfMaxima = other.numberOfMaxima;
      findNotesQuantize = other.findNotesQuantize;
#endif
 
      // Invalidate the caches
      DestroyWindows();
   }
   return *this;
}
 
SpectrogramSettings& SpectrogramSettings::defaults()
{
   static SpectrogramSettings instance;
   return instance;
}
 
//static
const EnumValueSymbols &SpectrogramSettings::GetScaleNames()
{
   static const EnumValueSymbols result{
      // Keep in correspondence with enum SpectrogramSettings::ScaleType:
      XO("Linear") ,
      XO("Logarithmic") ,
      /* i18n-hint: The name of a frequency scale in psychoacoustics */
      XO("Mel") ,
      /* i18n-hint: The name of a frequency scale in psychoacoustics, named for Heinrich Barkhausen */
      XO("Bark") ,
      /* i18n-hint: The name of a frequency scale in psychoacoustics, abbreviates Equivalent Rectangular Bandwidth */
      XO("ERB") ,
      /* i18n-hint: Time units, that is Period = 1 / Frequency */
      XO("Period") ,
   };
   return result;
}
 
//static
const EnumValueSymbols &SpectrogramSettings::GetColorSchemeNames()
{
   static const EnumValueSymbols result{
      // Keep in correspondence with enum SpectrogramSettings::ColorScheme:
      /* i18n-hint: New color scheme for spectrograms, Roseus is proper name of the color scheme */
      { wxT("SpecColorNew"),     XC("Color (Roseus)",    "spectrum prefs") },
      /* i18n-hint: Classic color scheme(from theme) for spectrograms */
      { wxT("SpecColorTheme"),   XC("Color (classic)",   "spectrum prefs") },
      /* i18n-hint: Grayscale color scheme for spectrograms */
      { wxT("SpecGrayscale"),    XC("Grayscale",         "spectrum prefs") },
      /* i18n-hint: Inverse grayscale color scheme for spectrograms */
      { wxT("SpecInvGrayscale"), XC("Inverse grayscale", "spectrum prefs") },
   };
 
   wxASSERT(csNumColorScheme == result.size());
   static_assert(csNumColorScheme == AColor::colorSchemes, "Broken correspondence");
 
   return result;
}
 
 
void SpectrogramSettings::ColorSchemeEnumSetting::Migrate(wxString &value)
{
   // Migrate old grayscale option to Color scheme choice
   bool isGrayscale = SpectrumGrayscale.Read();
   if (isGrayscale && !gPrefs->Read(wxT("/Spectrum/ColorScheme"), &value)) {
      value = GetColorSchemeNames().at(csGrayscale).Internal();
      Write(value);
      gPrefs->Flush();
   }
}
 
SpectrogramSettings::ColorSchemeEnumSetting SpectrogramSettings::colorSchemeSetting{
   wxT("/Spectrum/ColorScheme"),
   GetColorSchemeNames(),
   csColorNew, // default to Color(New)
   { csColorNew, csColorTheme, csGrayscale, csInvGrayscale },
};
 
 
//static
const TranslatableStrings &SpectrogramSettings::GetAlgorithmNames()
{
   static const TranslatableStrings results{
      // Keep in correspondence with enum SpectrogramSettings::Algorithm:
      XO("Frequencies") ,
      /* i18n-hint: the Reassignment algorithm for spectrograms */
      XO("Reassignment") ,
      /* i18n-hint: EAC abbreviates "Enhanced Autocorrelation" */
      XO("Pitch (EAC)") ,
   };
   return results;
}
 
bool SpectrogramSettings::Validate(bool quiet)
{
   if (!quiet &&
      maxFreq < 100) {
      AudacityMessageBox( XO("Maximum frequency must be 100 Hz or above") );
      return false;
   }
   else
      maxFreq = std::max(100, maxFreq);
 
   if (!quiet &&
      minFreq < 0) {
      AudacityMessageBox( XO("Minimum frequency must be at least 0 Hz") );
      return false;
   }
   else
      minFreq = std::max(0, minFreq);
 
   if (!quiet &&
      maxFreq <= minFreq) {
      AudacityMessageBox( XO(
"Minimum frequency must be less than maximum frequency") );
      return false;
   }
   else
      maxFreq = std::max(1 + minFreq, maxFreq);
 
   if (!quiet &&
      range <= 0) {
      AudacityMessageBox( XO("The range must be at least 1 dB") );
      return false;
   }
   else
      range = std::max(1, range);
 
   if (!quiet &&
      frequencyGain < 0) {
      AudacityMessageBox( XO("The frequency gain cannot be negative") );
      return false;
   }
   else if (!quiet &&
      frequencyGain > 60) {
      AudacityMessageBox( XO(
"The frequency gain must be no more than 60 dB/dec") );
      return false;
   }
   else
      frequencyGain =
         std::max(0, std::min(60, frequencyGain));
 
   // The rest are controlled by drop-down menus so they can't go wrong
   // in the Preferences dialog, but we also come here after reading fom saved
   // preference files, which could be or from future versions.  Validate quietly.
   windowType =
      std::max(0, std::min(NumWindowFuncs() - 1, windowType));
   scaleType =
      ScaleType(std::max(0,
         std::min((int)(SpectrogramSettings::stNumScaleTypes) - 1,
            (int)(scaleType))));
   colorScheme = ColorScheme(
      std::max(0, std::min<int>(csNumColorScheme-1, colorScheme))
   );
   algorithm = Algorithm(
      std::max(0, std::min((int)(algNumAlgorithms) - 1, (int)(algorithm)))
   );
   ConvertToEnumeratedWindowSizes();
   ConvertToActualWindowSizes();
 
   return true;
}
 
void SpectrogramSettings::LoadPrefs()
{
   minFreq = SpectrumMinFreq.Read();
 
   maxFreq = SpectrumMaxFreq.Read();
 
   range = SpectrumRange.Read();
   gain = SpectrumGain.Read();
   frequencyGain = SpectrumFrequencyGain.Read();
 
   windowSize = SpectrumFFTSize.Read();
 
   zeroPaddingFactor = SpectrumZeroPaddingFactor.Read();
 
   windowType = SpectrumWindowFunction.Read();
 
   colorScheme = colorSchemeSetting.ReadEnum();
 
   scaleType = static_cast<ScaleType>(SpectrumScale.Read());
 
#ifndef SPECTRAL_SELECTION_GLOBAL_SWITCH
   spectralSelection = SpectrumEnableSelection.Read();
#endif
 
   algorithm = static_cast<Algorithm>(SpectrumAlgorithm.Read());
 
#ifdef EXPERIMENTAL_FFT_Y_GRID
   fftYGrid = SpectrumYGrid.Read();
#endif //EXPERIMENTAL_FFT_Y_GRID
 
#ifdef EXPERIMENTAL_FIND_NOTES
   fftFindNotes = SpectrumFindNotes.Read();
   findNotesMinA = SpectrumFindNotesMinA.Read();
   numberOfMaxima = SpectrumFindNotesN.Read();
   findNotesQuantize = SpectrumFindNotesQuantize.Read();
#endif //EXPERIMENTAL_FIND_NOTES
 
   // Enforce legal values
   Validate(true);
 
   InvalidateCaches();
}
 
void SpectrogramSettings::SavePrefs()
{
   SpectrumMinFreq.Write(minFreq);
   SpectrumMaxFreq.Write(maxFreq);
 
   // Nothing wrote these.  They only varied from the linear scale bounds in-session. -- PRL
   // gPrefs->Write(wxT("/SpectrumLog/MaxFreq"), logMinFreq);
   // gPrefs->Write(wxT("/SpectrumLog/MinFreq"), logMaxFreq);
 
   SpectrumRange.Write(range);
   SpectrumGain.Write(gain);
   SpectrumFrequencyGain.Write(frequencyGain);
 
   SpectrumFFTSize.Write(windowSize);
 
   SpectrumZeroPaddingFactor.Write(zeroPaddingFactor);
 
   SpectrumWindowFunction.Write(windowType);
 
   colorSchemeSetting.WriteEnum(colorScheme);
 
   SpectrumScale.Write(static_cast<int>(scaleType));
 
#ifndef SPECTRAL_SELECTION_GLOBAL_SWITCH
   SpectrumEnableSelection.Write(spectralSelection);
#endif
 
   SpectrumAlgorithm.Write(static_cast<int>(algorithm));
 
#ifdef EXPERIMENTAL_FFT_Y_GRID
   SpectrumYGrid.Write(fftYGrid);
#endif //EXPERIMENTAL_FFT_Y_GRID
 
#ifdef EXPERIMENTAL_FIND_NOTES
   SpectrumFindNotes.Write(fftFindNotes);
   SpectrumFindNotesMinA.Write(findNotesMinA);
   SpectrumFindNotesN.Write(numberOfMaxima);
   SpectrumFindNotesQuantize.Write(findNotesQuantize);
#endif //EXPERIMENTAL_FIND_NOTES
}
 
// This is a temporary hack until SpectrogramSettings gets fully integrated
void SpectrogramSettings::UpdatePrefs()
{
   if (minFreq == defaults().minFreq)
      minFreq = SpectrumMinFreq.Read();
 
   if (maxFreq == defaults().maxFreq)
      maxFreq = SpectrumMaxFreq.Read();
 
   if (range == defaults().range)
      range = SpectrumRange.Read();
 
   if (gain == defaults().gain)
      gain = SpectrumGain.Read();
 
   if (frequencyGain == defaults().frequencyGain)
      frequencyGain = SpectrumFrequencyGain.Read();
 
   if (windowSize == defaults().windowSize)
      windowSize = SpectrumFFTSize.Read();
 
   if (zeroPaddingFactor == defaults().zeroPaddingFactor)
      zeroPaddingFactor = SpectrumZeroPaddingFactor.Read();
 
   if (windowType == defaults().windowType)
      windowType = SpectrumWindowFunction.Read();
 
   if (colorScheme == defaults().colorScheme) {
      colorScheme = colorSchemeSetting.ReadEnum();
   }
 
   if (scaleType == defaults().scaleType)
      scaleType = static_cast<ScaleType>(SpectrumScale.Read());
 
#ifndef SPECTRAL_SELECTION_GLOBAL_SWITCH
   if (spectralSelection == defaults().spectralSelection)
      spectralSelection = SpectrumEnableSelection.Read();
#endif
 
   if (algorithm == defaults().algorithm)
      algorithm = static_cast<Algorithm>(SpectrumAlgorithm.Read());
 
#ifdef EXPERIMENTAL_FFT_Y_GRID
   if (fftYGrid == defaults().fftYGrid)
      fftYGrid = SpectrumYGrid.Read();
#endif //EXPERIMENTAL_FFT_Y_GRID
 
#ifdef EXPERIMENTAL_FIND_NOTES
   if (fftFindNotes == defaults().fftFindNotes)
      fftFindNotes = SpectrumFindNotes.Read();
 
   if (findNotesMinA == defaults().findNotesMinA)
      findNotesMinA = SpectrumFindNotesMinA.Read();
 
   if (numberOfMaxima == defaults().numberOfMaxima)
      numberOfMaxima = SpectrumFindNotesN.Read();
 
   if (findNotesQuantize == defaults().findNotesQuantize)
      findNotesQuantize = SpectrumFindNotesQuantize.Read();
#endif //EXPERIMENTAL_FIND_NOTES
 
   // Enforce legal values
   Validate(true);
}
 
void SpectrogramSettings::InvalidateCaches()
{
   DestroyWindows();
}
 
SpectrogramSettings::~SpectrogramSettings()
{
   DestroyWindows();
}
 
auto SpectrogramSettings::Clone() const -> PointerType
{
   return std::make_unique<SpectrogramSettings>(*this);
}
 
void SpectrogramSettings::DestroyWindows()
{
   hFFT.reset();
   window.reset();
   dWindow.reset();
   tWindow.reset();
}
 
 
namespace
{
   enum { WINDOW, TWINDOW, DWINDOW };
   void RecreateWindow(
      Floats &window, int which, size_t fftLen,
      size_t padding, int windowType, size_t windowSize, double &scale)
   {
      // Create the requested window function
      window = Floats{ fftLen };
      size_t ii;
 
      const bool extra = padding > 0;
      wxASSERT(windowSize % 2 == 0);
      if (extra)
         // For windows that do not go to 0 at the edges, this improves symmetry
         ++windowSize;
      const size_t endOfWindow = padding + windowSize;
      // Left and right padding
      for (ii = 0; ii < padding; ++ii) {
         window[ii] = 0.0;
         window[fftLen - ii - 1] = 0.0;
      }
      // Default rectangular window in the middle
      for (; ii < endOfWindow; ++ii)
         window[ii] = 1.0;
      // Overwrite middle as needed
      switch (which) {
      case WINDOW:
         NewWindowFunc(windowType, windowSize, extra, window.get() + padding);
         break;
      case TWINDOW:
         NewWindowFunc(windowType, windowSize, extra, window.get() + padding);
         {
            for (int jj = padding, multiplier = -(int)windowSize / 2; jj < (int)endOfWindow; ++jj, ++multiplier)
               window[jj] *= multiplier;
         }
         break;
      case DWINDOW:
         DerivativeOfWindowFunc(windowType, windowSize, extra, window.get() + padding);
         break;
      default:
         wxASSERT(false);
      }
      // Scale the window function to give 0dB spectrum for 0dB sine tone
      if (which == WINDOW) {
         scale = 0.0;
         for (ii = padding; ii < endOfWindow; ++ii)
            scale += window[ii];
         if (scale > 0)
            scale = 2.0 / scale;
      }
      for (ii = padding; ii < endOfWindow; ++ii)
         window[ii] *= scale;
   }
}
 
void SpectrogramSettings::CacheWindows()
{
   if (hFFT == NULL || window == NULL) {
 
      double scale;
      auto factor = ZeroPaddingFactor();
      const auto fftLen = WindowSize() * factor;
      const auto padding = (WindowSize() * (factor - 1)) / 2;
 
      hFFT = GetFFT(fftLen);
      RecreateWindow(window, WINDOW, fftLen, padding, windowType, windowSize, scale);
      if (algorithm == algReassignment) {
         RecreateWindow(tWindow, TWINDOW, fftLen, padding, windowType, windowSize, scale);
         RecreateWindow(dWindow, DWINDOW, fftLen, padding, windowType, windowSize, scale);
      }
   }
}
 
void SpectrogramSettings::ConvertToEnumeratedWindowSizes()
{
   unsigned size;
   int logarithm;
 
   logarithm = -LogMinWindowSize;
   size = unsigned(windowSize);
   while (size > 1)
      size >>= 1, ++logarithm;
   windowSize = std::max(0, std::min(NumWindowSizes - 1, logarithm));
 
   // Choices for zero padding begin at 1
   logarithm = 0;
   size = unsigned(zeroPaddingFactor);
   while (zeroPaddingFactor > 1)
      zeroPaddingFactor >>= 1, ++logarithm;
   zeroPaddingFactor = std::max(0,
      std::min(LogMaxWindowSize - (windowSize + LogMinWindowSize),
         logarithm
   ));
}
 
void SpectrogramSettings::ConvertToActualWindowSizes()
{
   windowSize = 1 << (windowSize + LogMinWindowSize);
   zeroPaddingFactor = 1 << zeroPaddingFactor;
}
 
float SpectrogramSettings::findBin( float frequency, float binUnit ) const
{
   float linearBin = frequency / binUnit;
   if (linearBin < 0)
      return -1;
   else
      return linearBin;
}
 
size_t SpectrogramSettings::GetFFTLength() const
{
//#ifndef EXPERIMENTAL_ZERO_PADDED_SPECTROGRAMS
  // return windowSize;
//#else
   return windowSize * ((algorithm != algPitchEAC) ? zeroPaddingFactor : 1);
//#endif
}
 
size_t SpectrogramSettings::NBins() const
{
   // Omit the Nyquist frequency bin
   return GetFFTLength() / 2;
}
 
NumberScale SpectrogramSettings::GetScale( float minFreqIn, float maxFreqIn ) const
{
   NumberScaleType type = nstLinear;
 
   // Don't assume the correspondence of the enums will remain direct in the future.
   // Do this switch.
   switch (scaleType) {
   default:
      wxASSERT(false);
   case stLinear:
      type = nstLinear; break;
   case stLogarithmic:
      type = nstLogarithmic; break;
   case stMel:
      type = nstMel; break;
   case stBark:
      type = nstBark; break;
   case stErb:
      type = nstErb; break;
   case stPeriod:
      type = nstPeriod; break;
   }
 
   return NumberScale(type, minFreqIn, maxFreqIn);
}
 
bool SpectrogramSettings::SpectralSelectionEnabled() const
{
#ifdef SPECTRAL_SELECTION_GLOBAL_SWITCH
   return Globals::Get().spectralSelection;
#else
   return spectralSelection;
#endif
}
 
static const ChannelGroup::Attachments::RegisteredFactory
key2{ [](auto &) { return std::make_unique<SpectrogramBounds>(); } };
 
SpectrogramBounds &SpectrogramBounds::Get( WaveTrack &track )
{
   return track.Attachments::Get<SpectrogramBounds>(key2);
}
 
const SpectrogramBounds &SpectrogramBounds::Get(
   const WaveTrack &track )
{
   return Get(const_cast<WaveTrack&>(track));
}
 
SpectrogramBounds &SpectrogramBounds::Get(WaveChannel &channel)
{
   return Get(channel.GetTrack());
}
 
const SpectrogramBounds &SpectrogramBounds::Get(const WaveChannel &channel)
{
   return Get(const_cast<WaveChannel&>(channel));
}
 
SpectrogramBounds::~SpectrogramBounds() = default;
 
auto SpectrogramBounds::Clone() const -> PointerType
{
   return std::make_unique<SpectrogramBounds>(*this);
}
 
void SpectrogramBounds::GetBounds(
   const WaveChannel &wc, float &min, float &max) const
{
   auto &wt = wc.GetTrack();
   const double rate = wt.GetRate();
 
   const auto &settings = SpectrogramSettings::Get(wt);
   const auto type = settings.scaleType;
 
   const float top = (rate / 2.);
 
   float bottom;
   if (type == SpectrogramSettings::stLinear)
      bottom = 0.0f;
   else if (type == SpectrogramSettings::stPeriod) {
      // special case
      const auto half = settings.GetFFTLength() / 2;
      // EAC returns no data for below this frequency:
      const float bin2 = rate / half;
      bottom = bin2;
   }
   else
      // logarithmic, etc.
      bottom = 1.0f;
 
   {
      float spectrumMax = mSpectrumMax;
      if (spectrumMax < 0)
         spectrumMax = settings.maxFreq;
      if (spectrumMax < 0)
         max = top;
      else
         max = std::clamp(spectrumMax, bottom, top);
   }
 
   {
      float spectrumMin = mSpectrumMin;
      if (spectrumMin < 0)
         spectrumMin = settings.minFreq;
      if (spectrumMin < 0)
         min = std::max(bottom, top / 1000.0f);
      else
         min = std::clamp(spectrumMin, bottom, top);
   }
}