dynamic fft scaling

src/main.rs

@@ -51,6 +51,8 @@ fn main() -> color_eyre::Result<()> {
     let fft = planner.plan_fft_forward(buffer_size as usize);
     let mut fft_input = fft.make_input_vec();
     let mut fft_output = fft.make_output_vec();
+    let mut previous_sample_smth = 0.0;
+    let mut previous_magnitude = 1.0;
     let (sender, receiver) = mpsc::channel();
 
     let stream = device.build_input_stream(
@@ -61,6 +63,8 @@ fn main() -> color_eyre::Result<()> {
             &mut fft_input,
             &mut fft_output,
             config.sample_rate.0,
+            &mut previous_sample_smth,
+            &mut previous_magnitude,
         ) {
             Ok(packet) => {
                 if let Err(e) = sender.send(packet) {
@@ -79,7 +83,6 @@ fn main() -> color_eyre::Result<()> {
 
     stream.play()?;
 
-    let mut previous_sample_smth = 0.0;
     loop {
         let mut data = receiver.recv()?;
         data.sample_smth = 0.8f32.mul_add(previous_sample_smth, 0.2 * data.sample_raw);
@@ -168,6 +171,8 @@ impl AudioSyncPacket {
         fft_input: &mut [f32],
         fft_output: &mut [Complex32],
         sample_rate: u32,
+        previous_sample_smth: &mut f32,
+        previous_magnitude: &mut f32,
     ) -> Result<Self> {
         // take the absolute value of the audio data
         let abs_data: Vec<_> = data.iter().map(|sample| sample.abs()).collect();
@@ -215,24 +220,27 @@ impl AudioSyncPacket {
 
         // scale the fft values to u8
         let mut fft_values_u8 = [0u8; 16];
-        let mut fft_max = fft_values
+        let fft_max = fft_values
             .iter()
             .max_by(|lhs, rhs| lhs.partial_cmp(rhs).unwrap_or(Ordering::Equal))
             .copied()
-            .unwrap_or(1.0);
-        if fft_max == 0.0 {
-            fft_max = 1.0;
-        }
+            .unwrap_or(1.0)
+            .max(1.0);
+        let magnitude = fft_max.max(*previous_magnitude * 0.99);
+        *previous_magnitude = magnitude;
         for i in 0..fft_values.len() {
-            fft_values_u8[i] = (fft_values[i] * f32::from(u8::MAX) / fft_max).saturating_as();
+            fft_values_u8[i] = (fft_values[i] * f32::from(u8::MAX) / magnitude).saturating_as();
         }
 
         // calculate fft magnitude sum
         let fft_magnitude_sum = real_fft_output.iter().sum::<f32>();
 
+        let sample_smth = 0.8f32.mul_add(*previous_sample_smth, 0.2 * raw_level);
+        *previous_sample_smth = sample_smth;
+
         Ok(Self::new(
             raw_level,
-            0.0,
+            sample_smth,
             peak_level,
             fft_values_u8,
             fft_magnitude_sum,