GUI, lists PA devices, backend can watch audio stream

1 files changed, 53 insertions, 0 deletions

diff --git a/src/transforms.rs b/src/transforms.rs
new file mode 100644
index 0000000..6b491ac
--- /dev/null
+++ b/src/transforms.rs
@@ -0,0 +1,53 @@
+extern crate dft;
+
+#[derive(Clone, Debug)]
+pub struct FrequencyBucket {
+    pub min_freq: f64,
+    pub max_freq: f64,
+    pub intensity: f64
+}
+
+pub fn fft(input: Vec<f64>, sample_rate: f64) -> Vec<FrequencyBucket> {
+    let frames = input.len();
+    let plan = dft::Plan::new(dft::Operation::Forward, frames);
+    let mut intensities = input.clone();
+    dft::transform(&mut intensities, &plan);
+
+    let frequency_resolution = sample_rate / 2.0 / frames as f64;
+    
+    intensities.iter().enumerate().map(|(index, &value)| {
+        let index = index as f64;
+        FrequencyBucket {
+            min_freq: index * frequency_resolution,
+            max_freq: (index+1.0) * frequency_resolution,
+            intensity: value
+        }
+    }).collect()
+}
+
+#[test]
+fn fft_on_sine_wave() {
+    use std::f64::consts;
+    
+    let sample_rate = 44100.0 as f64;
+    let amplitude = 1.0 as f64;
+    let frames = 16384;
+    let frequency = 10000.0 as f64; //10KHz
+    let samples = (0..frames)
+        .map(|x| {
+            let t = x as f64 / sample_rate;
+            (2.0 as f64 * consts::PI * frequency * t).sin() * amplitude
+        }).collect();
+
+    let result = fft(samples, sample_rate);
+
+    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();
+
+    println!("{:?}", peak);
+
+    assert!(peak.min_freq <= frequency);
+    assert!(peak.max_freq >= frequency);
+}