Index: apps/plugins/pitch_detector.c
===================================================================
--- apps/plugins/pitch_detector.c	(Revision 22718)
+++ apps/plugins/pitch_detector.c	(Arbeitskopie)
@@ -177,7 +177,39 @@
     float2fixed(0.45),
     float2fixed(0.50),
 };
+
+
+/* Structure for the reference frequency (frequency of A)
+ * It's used for scaling the frequency before finding out
+ * the note. The frequency is scaled in a way that the main
+ * algorithm can assume the frequency of A to be 440 Hz.
+ */
+struct freq_A_entry
+{
+    const int frequency;  /* Frequency in Hz */
+    const fixed ratio;    /* 440/frequency   */
+    const fixed logratio; /* log2(factor)    */
+};
+
+const struct freq_A_entry freq_A[] =
+{
+    {435, float2fixed(1.011363636), float2fixed( 0.016301812)},
+    {436, float2fixed(1.009090909), float2fixed( 0.013056153)},
+    {437, float2fixed(1.006818182), float2fixed( 0.009803175)},
+    {438, float2fixed(1.004545455), float2fixed( 0.006542846)},
+    {439, float2fixed(1.002272727), float2fixed( 0.003275132)},
+    {440, float2fixed(1.000000000), float2fixed( 0.000000000)},
+    {441, float2fixed(0.997727273), float2fixed(-0.003282584)},
+    {442, float2fixed(0.995454545), float2fixed(-0.006572654)},
+    {443, float2fixed(0.993181818), float2fixed(-0.009870244)},
+    {444, float2fixed(0.990909091), float2fixed(-0.013175389)},
+    {445, float2fixed(0.988636364), float2fixed(-0.016488123)},
+};
 
+/* Index of the entry for 440 Hz in the table (default frequency for A) */
+#define DEFAULT_FREQ_A 5
+#define NUM_FREQ_A (sizeof(freq_A)/sizeof(freq_A[0]))
+
 /* How loud the audio has to be to start displaying pitch  */
 /* Must be between 0 and 100                               */
 #define VOLUME_THRESHOLD (50)
@@ -279,6 +311,7 @@
     unsigned sample_size;
     unsigned lowest_freq;
     unsigned yin_threshold;
+    unsigned freq_A; /* Index of the frequency of A */
     bool use_sharps;
     bool display_hz;
 } tuner_settings;
@@ -325,6 +358,7 @@
     settings->sample_size = BUFFER_SIZE;
     settings->lowest_freq = period2freq(BUFFER_SIZE / 4);
     settings->yin_threshold = DEFAULT_YIN_THRESHOLD;
+    settings->freq_A = DEFAULT_FREQ_A;
     settings->use_sharps = true;
     settings->display_hz = false;
 }
@@ -426,6 +460,23 @@
     { "0.50", -1 },
 };
 
+/* These are the display frequency options for note A */
+
+static const struct opt_items freq_A_text[] =
+{
+    { "435", -1 },
+    { "436", -1 },
+    { "437", -1 },
+    { "438", -1 },
+    { "439", -1 },
+    { "440", -1 },
+    { "441", -1 },
+    { "442", -1 },
+    { "443", -1 },
+    { "444", -1 },
+    { "445", -1 },
+};
+
 static const struct opt_items accidental_text[] = 
 {
     { "Flat", -1 },
@@ -469,6 +520,7 @@
                         "Accidentals",
                         "Display Frequency (Hz)",
                         "Reset Settings",
+                        "Frequency of A (Hz)",
                         "Quit");
 
     while(!done)
@@ -519,13 +571,20 @@
                                BOOL, noyes_text, 2, tuner_settings_reset_query);
                 break;
             case 8:
+                rb->set_option(
+                    "Frequency of A (Hz)",
+                    &tuner_settings.freq_A,
+                    INT, freq_A_text,
+                    sizeof(freq_A_text) / sizeof(freq_A_text[0]),
+                    NULL);
+                break;
+            case 9:
                 exit_tuner = true;
             case 0: 
             default:
                 /* Return to the tuner */
                 done = true;
                 break;
-
         }
     }
     return(exit_tuner);
@@ -650,11 +709,11 @@
     int x;
 
 #ifdef HAVE_LCD_COLOR
-    rb->lcd_set_foreground(LCD_RGBPACK(255,255,255));	/* Color screens */
+    rb->lcd_set_foreground(LCD_RGBPACK(255,255,255)); /* Color screens */
 #elif LCD_DEPTH > 1
     rb->lcd_set_foreground(LCD_BLACK);      /* Greyscale screens */
 #else
-    rb->lcd_set_foreground(LCD_BLACK);		/* Black and white screens */
+    rb->lcd_set_foreground(LCD_BLACK);      /* Black and white screens */
 #endif
 
     rb->lcd_hline(0,LCD_WIDTH-1, BAR_HLINE_Y);
@@ -702,14 +761,26 @@
 {                                                     
     fixed ldf, mldf;
     fixed lfreq, nfreq;
+    fixed orig_freq;
     int i, note = 0;
     char str_buf[30];
 
     if (fp_lt(freq, FP_LOW))
         freq = FP_LOW;
-    lfreq = log(freq);
-
-    /* Get the frequency to within the range of our reference table */
+    
+    /* We calculate the frequency and its log as if */
+    /* the reference frequency of A were 440 Hz.    */
+    lfreq = log(freq);
+    orig_freq = freq;
+    if (tuner_settings.freq_A != DEFAULT_FREQ_A)
+    {
+        lfreq = fp_add(lfreq, freq_A[tuner_settings.freq_A].logratio);
+        freq = fp_mul(freq, freq_A[tuner_settings.freq_A].ratio);
+    }
+
+    /* This calculates a log freq offset for note A */
+    /* Get the frequency to within the range of our reference table, */
+    /* i.e. into the right octave.                                   */
     while (fp_lt(lfreq, fp_sub(lfreqs[0], fp_shr(LOG_D_NOTE, 1))))
         lfreq = fp_add(lfreq, LOG_2);
     while (fp_gte(lfreq, fp_sub(fp_add(lfreqs[0], LOG_2), 
@@ -722,19 +793,17 @@
                  fp_sub(lfreq,lfreqs[i]) : fp_neg(fp_sub(lfreq,lfreqs[i]));
         if (fp_lt(ldf, mldf)) 
         {
-              mldf = ldf;
-              note = i;
+            mldf = ldf;
+            note = i;
         }
     }
     nfreq = freqs[note];
-    while (fp_gt(fp_div(nfreq, freq), D_NOTE_SQRT)) 
+    while (fp_gt(fp_div(nfreq, freq), D_NOTE_SQRT))
         nfreq = fp_shr(nfreq, 1);
     while (fp_gt(fp_div(freq, nfreq), D_NOTE_SQRT))
-    {
         nfreq = fp_shl(nfreq, 1);
-    }
     
-    ldf=fp_mul(int2fixed(1200), log(fp_div(freq,nfreq)));
+    ldf = fp_mul(int2fixed(1200), log(fp_div(freq,nfreq)));
 
     rb->lcd_clear_display();
     draw_bar(ldf);                /* The red bar */
@@ -744,8 +813,8 @@
         if(tuner_settings.display_hz)
         {
             rb->snprintf(str_buf,30, "%s : %d cents (%d.%02dHz)", 
-                         notes[note], fp_round(ldf) ,fixed2int(freq),
-                         fp_round(fp_mul(fp_frac(freq), 
+                         notes[note], fp_round(ldf) ,fixed2int(orig_freq),
+                         fp_round(fp_mul(fp_frac(orig_freq),
                                          int2fixed(DISPLAY_HZ_PRECISION))));
             print_str(str_buf);
         }