1 files changed, 63 insertions, 10 deletions

diff --git a/src/transforms.rs b/src/transforms.rs
index 16478df..371379d 100644
--- a/src/transforms.rs
+++ b/src/transforms.rs
@@ -25,6 +25,18 @@ pub fn fft(input: Vec<f64>, sample_rate: f64) -> Vec<FrequencyBucket> {
     }).collect()
 }
 
+pub fn find_fundamental_frequency(frequency_domain: &Vec<FrequencyBucket>) -> Option<f64> {
+    //TODO look at all significant frequencies, find fundamental
+    //TODO return None is none of them are significant
+    
+    let max_frequency = frequency_domain.iter()
+        .fold(None as Option<::transforms::FrequencyBucket>, |max, next|
+              if max.is_none() || max.clone().unwrap().intensity < next.intensity { Some(next.clone()) } else { max }
+        ).unwrap().max_freq;
+    
+    Some(max_frequency)
+}
+
 #[test]
 fn fft_on_sine_wave() {
     use std::f64::consts;
@@ -33,6 +45,8 @@ fn fft_on_sine_wave() {
     let amplitude = 1.0 as f64;
     let frames = 16384;
     let frequency = 10000.0 as f64; //10KHz
+    let frequency_resolution = sample_rate / 2.0 / frames as f64;
+    
     let samples = (0..frames)
         .map(|x| {
             let t = x as f64 / sample_rate;
@@ -40,19 +54,58 @@ fn fft_on_sine_wave() {
         }).collect();
 
     let result = fft(samples, sample_rate);
+    let fundamental = find_fundamental_frequency(&result);
 
-    let peak = result.iter()
-        .fold(None as Option<FrequencyBucket>, |max, next|
-              if max.is_none() || max.clone().unwrap().intensity < next.intensity { Some(next.clone()) } else { max }
-        ).unwrap();
+    assert!((fundamental-frequency).abs() < frequency_resolution, "expected={}, actual={}", frequency, fundamental);
+}
+
+pub fn hz_to_pitch(hz: f64) -> String {
+    let pitch_names = [
+        "C",
+        "C#",
+        "D",
+        "Eb",
+        "E",
+        "F",
+        "F#",
+        "G",
+        "G#",
+        "A",
+        "Bb",
+        "B"
+    ];
+
+    let midi_number = 69.0 + 12.0 * (hz / 440.0).log2();
+    //midi_number of 0 is C-1.
 
-    println!("{:?}", peak);
+    let rounded_pitch = midi_number.round() as usize;
+    let name = pitch_names[rounded_pitch%pitch_names.len()].to_string();
+    let octave = rounded_pitch / pitch_names.len() - 1; //0 is C-1
 
-    assert!(peak.min_freq <= frequency);
-    assert!(peak.max_freq >= frequency);
+    let mut cents = ((midi_number * 100.0).round() % 100.0) as i32;
+    if cents >= 50 {
+        cents -= 100;
+    }
+    
+    format!("{}{} {:+}", name, octave, cents)
 }
 
-pub fn hz_to_pitch(hz: f64) -> String {
-    let pitch_number = 49.0 + 12.0 * (hz / 440.0).log2();
-    pitch_number.floor().to_string()
+#[test]
+fn a4_is_correct() {
+    assert_eq!(hz_to_pitch(440.0), "A4 +0");
+}
+
+#[test]
+fn a2_is_correct() {
+    assert_eq!(hz_to_pitch(110.0), "A2 +0");
+}
+
+#[test]
+fn c4_is_correct() {
+    assert_eq!(hz_to_pitch(261.63), "C4 +0");
+}
+
+#[test]
+fn f5_is_correct() {
+    assert_eq!(hz_to_pitch(698.46), "F5 +0");
 }