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src/pitch/pitchyinfft.c: simplify, add some comment, update copyright

--- a/src/pitch/pitchyinfft.c

+++ b/src/pitch/pitchyinfft.c

@@ -1,5 +1,5 @@

 /*

-  Copyright (C) 2003-2009 Paul Brossier <piem@aubio.org>

+  Copyright (C) 2003-2013 Paul Brossier <piem@aubio.org>

   This file is part of aubio.

@@ -33,7 +33,6 @@

   fvec_t *sqrmag;     /**< square difference function */

   fvec_t *weight;     /**< spectral weighting window (psychoacoustic model) */

   fvec_t *fftout;     /**< Fourier transform output */

-  fvec_t *res;        /**< complex vector to compute square difference function */

   aubio_fft_t *fft;   /**< fft object to compute square difference function */

   fvec_t *yinfft;     /**< Yin function */

   smpl_t tol;         /**< Yin tolerance */

@@ -59,7 +58,6 @@

   p->winput = new_fvec (bufsize);

   p->fft = new_aubio_fft (bufsize);

   p->fftout = new_fvec (bufsize);

-  p->res = new_fvec (bufsize);

   p->sqrmag = new_fvec (bufsize);

   p->yinfft = new_fvec (bufsize / 2 + 1);

   p->tol = 0.85;

@@ -98,43 +96,50 @@

 aubio_pitchyinfft_do (aubio_pitchyinfft_t * p, fvec_t * input, fvec_t * output)

 {

   uint_t tau, l;

+  uint_t length = p->fftout->length;

   uint_t halfperiod;

-  smpl_t tmp, sum;

-  fvec_t *res = (fvec_t *) p->res;

-  fvec_t *yin = (fvec_t *) p->yinfft;

-  l = 0;

-  tmp = 0.;

-  sum = 0.;

+  fvec_t *fftout = p->fftout;

+  fvec_t *yin = p->yinfft;

+  smpl_t tmp = 0., sum = 0.;

+  // window the input

   for (l = 0; l < input->length; l++) {

     p->winput->data[l] = p->win->data[l] * input->data[l];

   }

-  aubio_fft_do_complex (p->fft, p->winput, p->fftout);

-  uint_t length = p->fftout->length;

-  p->sqrmag->data[0] = SQR(p->fftout->data[0]);

+  // get the real / imag parts of its fft

+  aubio_fft_do_complex (p->fft, p->winput, fftout);

+  // get the squared magnitude spectrum, applying some weight

+  p->sqrmag->data[0] = SQR(fftout->data[0]);

   p->sqrmag->data[0] *= p->weight->data[0];

   for (l = 1; l < length / 2; l++) {

-    p->sqrmag->data[l] = SQR(p->fftout->data[l]) + SQR(p->fftout->data[length - l]);

+    p->sqrmag->data[l] = SQR(fftout->data[l]) + SQR(fftout->data[length - l]);

     p->sqrmag->data[l] *= p->weight->data[l];

-    p->sqrmag->data[p->sqrmag->length - l] = p->sqrmag->data[l];

+    p->sqrmag->data[length - l] = p->sqrmag->data[l];

   }

-  p->sqrmag->data[length / 2] = SQR(p->fftout->data[length / 2]);

+  p->sqrmag->data[length / 2] = SQR(fftout->data[length / 2]);

   p->sqrmag->data[length / 2] *= p->weight->data[length / 2];

+  // get sum of weighted squared mags

   for (l = 0; l < length / 2 + 1; l++) {

     sum += p->sqrmag->data[l];

   }

   sum *= 2.;

-  aubio_fft_do_complex (p->fft, p->sqrmag, res);

+  // get the real / imag parts of the fft of the squared magnitude

+  aubio_fft_do_complex (p->fft, p->sqrmag, fftout);

   yin->data[0] = 1.;

   for (tau = 1; tau < yin->length; tau++) {

-    yin->data[tau] = sum - res->data[tau];

+    // compute the square differences

+    yin->data[tau] = sum - fftout->data[tau];

+    // and the cumulative mean normalized difference function

     tmp += yin->data[tau];

     yin->data[tau] *= tau / tmp;

   }

+  // find best candidates

   tau = fvec_min_elem (yin);

   if (yin->data[tau] < p->tol) {

-    /* no interpolation */

-    //return tau;

-    /* 3 point quadratic interpolation */

+    // no interpolation, directly return the period as an integer

+    //output->data[0] = tau;

+    //return;

+

+    // 3 point quadratic interpolation

     //return fvec_quadint_min(yin,tau,1);

     /* additional check for (unlikely) octave doubling in higher frequencies */

     if (tau > 35) {

@@ -160,7 +165,6 @@

   del_fvec (p->yinfft);

   del_fvec (p->sqrmag);

   del_fvec (p->fftout);

-  del_fvec (p->res);

   del_fvec (p->winput);

   del_fvec (p->weight);

   AUBIO_FREE (p);