StompTuner v0.5 released

brummer · June 8, 2024, 6:00pm

StompTuner, a Strobe Tuner in Stomp Box Format, release version 0.5

This Release fix a Sample Rate issue within the CLAP format, add the AU (Audio Unit) plugin format for macos, and introduce a new, reworked GUI.

StompTuner using the DISTRHO DPF Plugin Framework

2024-06-08_05-49

Project Page (Source Code):

Release Page (Binary Packages):

x42 · June 8, 2024, 7:05pm

Neat!

Is that only a GUI or does the underlying DSP also makes use of the strobe principle for extra precision while using the fundamental freq (…and to be used with a wide variety of instruments, as well as suitable for stretch turning)?

PS. Edit

Answered my own question by reading the source: DSP uses FFT, and peak finder. So no actual strobe.

…and love this comment

github.com

brummer10/StompTuner/blob/f213394fbcd2e0bc76885ed6820c39568be0fbd0/plugins/StompTuner/pitch_tracker.cpp#L365


      
          fftwf_execute(m_fftwPlanIFFT);
          
          
double sumSq = 2.0 * static_cast<double>(m_fftwBufferTime[0]) / static_cast<double>(m_fftSize);
          for (int k = 0; k < m_fftSize - m_buffersize; k++) {
              m_fftwBufferTime[k] = m_fftwBufferTime[k+1] / static_cast<float>(m_fftSize);
          }
          
          
int count = (m_buffersize + 1) / 2;
          for (int k = 0; k < count; k++) {
              sumSq  -= sq(m_input[m_buffersize-1-k]) + sq(m_input[k]);
              // dividing by zero is very slow, so deal with it seperately
              if (sumSq > 0.0) {
                  m_fftwBufferTime[k] *= 2.0 / sumSq;
              } else {
                  m_fftwBufferTime[k] = 0.0;
              }
          }
          const float thres = 0.99; // was 0.6
              int maxAutocorrIndex = findsubMaximum(m_fftwBufferTime, count, thres);
          
          
    float x = 0.0;

brummer · June 9, 2024, 1:40pm

Hi
Yes, it use FFT and go for (sub)maxima.
The strobe is handled in the tuner widget, the Pitch Tracker send only the detected frequency.

github.com

brummer10/StompTuner/blob/main/plugins/CairoWidgets/CairoTunerWidget.hpp#L64


      
              detectedNote = 0;
              detectedOctave = 0;
              cent = 0.0f;
              collectCents = 0.0f;
              collectMilliCents = 0.0f;
              fw = 0;
              cw = 0;
              refFreq = 440.0;
          }
          
          
void getNote()
          {
              if (detectedFrequency > 23.0f && detectedFrequency < 999.0f)
              {
          
          
        float fdetectedNote = 12.0 * (log2f(detectedFrequency/refFreq) + 4);
                  float fdetectedNoter = round(fdetectedNote);
                  int idetectedNote = fdetectedNoter;
                  int idetectedOctave = round((fdetectedNoter + 3)/12);
                  const int octsz = sizeof(octave) / sizeof(octave[0]);
                  if (idetectedOctave < 0 || idetectedOctave >= octsz) {

Cent and Note was then calculated in the widget thread. The strobe itself is driven by collected cents/millicents.

I’ve done a couple of comparison with the X42 tuna tuner, and both tuners showing the same results. Both been mostly accurate, just, when it comes to down-tuned strings below B1, both been a bit of (about 3 - 10 cents). Seems as if even fundamental Frequency couldn’t handle that right.

system · July 7, 2024, 1:41pm

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