- YIN estimator improvements:master

  - minimum detection now operates on interpolated values
  - period calculation now interpolates raw difference function, as interpolation of the normalized function is said to be slightly biased
  - added high threshold parameter, above which the result is ignored (no note detected)


git-svn-id: https://lampka.siedziba.pl:790/svn/repos/lingot-win32@314 455248ca-bdda-0310-9134-f4ebb693071a

1 files changed, 38 insertions, 20 deletions

diff --git a/src/lingot-yin.c b/src/lingot-yin.c
index 05eaa59..42e478e 100644
--- a/src/lingot-yin.c
+++ b/src/lingot-yin.c
@@ -34,41 +34,59 @@ inline FLT yin_sqr(FLT x)
 	return x*x;
 }
 
-inline FLT yin_interpolate_tau(FLT y1, FLT y2, FLT y3)
+inline FLT yin_interpolate_x(FLT y1, FLT y2, FLT y3)
 {
+	if ((y1 == y2) && (y2 == y3)) return 0;
 	return ((y1 - y3)/(2.0*(y3 + y1 - (2.0*y2))));
 }
 
-FLT yin(LingotCore* core) {
-	FLT dt_tau;
+inline FLT yin_interpolate_y(FLT y1, FLT y2, FLT y3)
+{
+	if ((y1 == y2) && (y2 == y3)) return y1;
+	return (((6.0 * y2) - y1 + (3.0 * y3) - (4.0 * yin_sqr(y2 - y3) / (y3 - (2.0 * y2) + y1))) / 8.0);
+}
+
+void yin(LingotCore* core) {
+	FLT dt_tau[3];
 	FLT dt_tau_sum = 0;
-	FLT dpt_right = 1.0/0.0, dpt_center, dpt_left;
-	FLT thr = core->conf->yin_threshold;
+	FLT dpt[3];
+	FLT thr_low = core->conf->yin_threshold_low;
+	FLT thr_high = core->conf->yin_threshold_high;
 	FLT dpt_min = 1.0/0.0;
-	FLT dpt_min_left, dpt_min_right;
-	int j, tau, tau_min;
+	FLT dpt_interpolated;
+	FLT tau_min;
+	int j, tau;
 	int len = core->conf->temporal_buffer_size / 2;
 
-	for (tau = 1; (tau < len) && ((dpt_center > thr) || (dpt_right < dpt_center) || (tau <= 2)); tau++)
+	for (tau = 1; tau < len; tau++)
 	{
-		dt_tau = 0;
+		dt_tau[0] = dt_tau[1];
+		dt_tau[1] = dt_tau[2];
+		dt_tau[2] = 0;
 		for (j = 0; j < len ; j++)
 		{
-			dt_tau += yin_sqr(core->temporal_buffer[j] - core->temporal_buffer[j+tau]);
+			dt_tau[2] += yin_sqr(core->temporal_buffer[j] - core->temporal_buffer[j+tau]);
 		}
-		dt_tau_sum += dt_tau;
+		dt_tau_sum += dt_tau[2];
 
-		dpt_left = dpt_center;
-		dpt_center = dpt_right;
-		dpt_right = dt_tau / ( 1.0 / tau * dt_tau_sum );
+		dpt[0] = dpt[1];
+		dpt[1] = dpt[2];
+		dpt[2] = dt_tau[2] / ( 1.0 / tau * dt_tau_sum );
 
-		if (dpt_center < dpt_min) 
+		if (tau >= 3)
 		{
-			dpt_min_left = dpt_left;
-			dpt_min = dpt_center;
-			dpt_min_right = dpt_right;
-			tau_min = tau - 1;
+			if ((dpt[1] <= dpt[0]) && (dpt[1] <= dpt[2]))
+			{
+// we have local minimum
+				dpt_interpolated = yin_interpolate_y(dpt[0], dpt[1], dpt[2]);
+				if (dpt_interpolated < dpt_min)
+				{
+					dpt_min = dpt_interpolated;
+					tau_min = (FLT)tau - 1 + yin_interpolate_x(dt_tau[0], dt_tau[1], dt_tau[2]);
+					if (dpt_min < thr_low) break;
+				}
+			}
 		}
 	}
-	return (FLT)tau_min + yin_interpolate_tau(dpt_min_left, dpt_min, dpt_min_right);
+	if ((tau_min > 1) && (dpt_min < thr_high)) core->freq = core->conf->sample_rate / (FLT)core->conf->oversampling / tau_min; else core->freq = 0;
 }