src/mathutils.h: add fvec_quadratic_peak_mag to find the magnitude of interpolated...

diff --git a/src/mathutils.c b/src/mathutils.c
index be89c98..766016c 100644 (file)
--- a/src/mathutils.c
+++ b/src/mathutils.c
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2003-2013 Paul Brossier <piem@aubio.org>
+  Copyright (C) 2003-2014 Paul Brossier <piem@aubio.org>
 
   This file is part of aubio.
 
@@ -429,6 +429,17 @@ smpl_t fvec_quadratic_peak_pos (fvec_t * x, uint_t pos) {
   return pos + 0.5 * (s0 - s2 ) / (s0 - 2.* s1 + s2);
 }
 
+smpl_t fvec_quadratic_peak_mag (fvec_t *x, smpl_t pos) {
+  smpl_t x0, x1, x2;
+  uint_t index = (uint_t)(pos - .5) + 1;
+  if (pos >= x->length || pos < 0.) return 0.;
+  if ((smpl_t)index == pos) return x->data[index];
+  x0 = x->data[index - 1];
+  x1 = x->data[index];
+  x2 = x->data[index + 1];
+  return x1 - .25 * (x0 - x2) * (pos - index);
+}
+
 uint_t fvec_peakpick(fvec_t * onset, uint_t pos) {
   uint_t tmp=0;
   tmp = (onset->data[pos] > onset->data[pos-1]

diff --git a/src/mathutils.h b/src/mathutils.h
index d4905a7..fe04647 100644 (file)
--- a/src/mathutils.h
+++ b/src/mathutils.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2003-2013 Paul Brossier <piem@aubio.org>
+  Copyright (C) 2003-2014 Paul Brossier <piem@aubio.org>
 
   This file is part of aubio.
 
@@ -234,6 +234,19 @@ smpl_t fvec_median (fvec_t * v);
 */
 smpl_t fvec_quadratic_peak_pos (fvec_t * x, uint_t p);
 
+/** finds magnitude of peak by quadratic interpolation
+
+  See [Quadratic Interpolation of Spectral
+  Peaks](https://ccrma.stanford.edu/~jos/sasp/Quadratic_Peak_Interpolation.html),
+  by Julius O. Smith III
+
+  \param x vector to get the magnitude of the interpolated peak position from
+  \param p index of the peak in vector `x`
+  \return magnitude of interpolated peak
+
+*/
+smpl_t fvec_quadratic_peak_mag (fvec_t * x, smpl_t p);
+
 /** Quadratic interpolation using Lagrange polynomial.
  
   Inspired from ``Comparison of interpolation algorithms in real-time sound