From 704724bb94970553226c3f2247a1045f4ef94a9e Mon Sep 17 00:00:00 2001
From: Walter Bender <walter.bender@gmail.com>
Date: Sat, 23 Jun 2012 20:40:03 +0000
Subject: improved logging of freq.

---
diff --git a/audiograb.py b/audiograb.py
index 745cceb..6f349ea 100644
--- a/audiograb.py
+++ b/audiograb.py
@@ -293,11 +293,18 @@ class AudioGrab():
 
     def _sample_frequency(self, data_buffer):
         ''' The maximum frequency in the sample '''
-        r = []
-        for j in rfft(data_buffer):
-            r.append(abs(j))
+        buf = rfft(data_buffer)
+        buf = abs(buf)
+        maxi = buf.argmax()
+        if maxi == 0:
+            pitch = 0.0
+        else:  # Simple interpolation
+            a, b, c = buf[maxi - 1], buf[maxi], buf[maxi + 1]
+            maxi -= a / float(a + b + c)
+            maxi += c / float(a + b + c)
+            pitch = maxi * 48000 / (len(buf) * 2)
         # Convert output to Hertz
-        return r.index(max(r)) * 48000. / len(data_buffer)
+        return pitch
 
     def _calibrate_resistance(self, data_buffer):
         ''' Return calibrated value for resistance '''
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