Feat: fix scope / spectrum / vumeter

src/engine/audio.rs

@@ -11,7 +11,7 @@ use std::thread::{self, JoinHandle};
 use super::AudioCommand;
 
 pub struct ScopeBuffer {
-    pub samples: [AtomicU32; 64],
+    pub samples: [AtomicU32; 256],
     peak_left: AtomicU32,
     peak_right: AtomicU32,
 }
@@ -29,12 +29,19 @@ impl ScopeBuffer {
         let mut peak_l: f32 = 0.0;
         let mut peak_r: f32 = 0.0;
 
+        // Calculate peaks from ALL input frames for accurate VU metering
+        for chunk in data.chunks(2) {
+            if let [left, right] = chunk {
+                peak_l = peak_l.max(left.abs());
+                peak_r = peak_r.max(right.abs());
+            }
+        }
+
+        // Downsample for scope display
+        let frames = data.len() / 2;
         for (i, atom) in self.samples.iter().enumerate() {
-            let idx = i * 2;
-            let left = data.get(idx).copied().unwrap_or(0.0);
-            let right = data.get(idx + 1).copied().unwrap_or(0.0);
-            peak_l = peak_l.max(left.abs());
-            peak_r = peak_r.max(right.abs());
+            let frame_idx = (i * frames) / self.samples.len();
+            let left = data.get(frame_idx * 2).copied().unwrap_or(0.0);
             atom.store(left.to_bits(), Ordering::Relaxed);
         }
 
@@ -42,7 +49,7 @@ impl ScopeBuffer {
         self.peak_right.store(peak_r.to_bits(), Ordering::Relaxed);
     }
 
-    pub fn read(&self) -> [f32; 64] {
+    pub fn read(&self) -> [f32; 256] {
         std::array::from_fn(|i| f32::from_bits(self.samples[i].load(Ordering::Relaxed)))
     }
 
@@ -146,7 +153,7 @@ impl SpectrumAnalyzer {
             let hi = self.band_edges[band + 1].max(lo + 1);
             let sum: f32 = self.fft_buf[lo..hi].iter().map(|c| c.norm()).sum();
             let avg = sum / (hi - lo) as f32;
-            let amplitude = avg / (FFT_SIZE as f32 / 2.0);
+            let amplitude = avg / (FFT_SIZE as f32 / 4.0);
             let db = 20.0 * amplitude.max(1e-10).log10();
             *mag = ((db + 60.0) / 60.0).clamp(0.0, 1.0);
         }