Add basic cepstral f0 detector #3

src/voyx/alg/CepstralPitchDetector.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <voyx/Header.h>
+
+template<typename T>
+class CepstralPitchDetector
+{
+
+public:
+
+  CepstralPitchDetector(const std::pair<voyx_t, voyx_t> roi, const voyx_t samplerate) :
+    roi(roi),
+    samplerate(samplerate)
+  {
+  }
+
+  voyx_t operator()(const voyx::vector<T> cepstrum) const
+  {
+    const size_t nmin = size_t(0);
+    const size_t nmax = cepstrum.size() / 2;
+
+    const size_t qmin = static_cast<size_t>(samplerate / roi.first);
+    const size_t qmax = static_cast<size_t>(samplerate / roi.second);
+
+    const size_t imin = std::clamp(std::min(qmin, qmax), nmin, nmax);
+    const size_t imax = std::clamp(std::max(qmin, qmax), nmin, nmax);
+
+    voyxassert(imin < imax);
+
+    T value = std::numeric_limits<T>::lowest();
+    ptrdiff_t index = -1;
+
+    for (size_t i = imin; i < imax; ++i)
+    {
+      if (cepstrum[i] > value)
+      {
+        value = cepstrum[i];
+        index = i;
+      }
+    }
+
+    return index ? samplerate / index : 0;
+  }
+
+private:
+
+  const std::pair<voyx_t, voyx_t> roi;
+  const voyx_t samplerate;
+
+};