groovebox: display input meters!

crates/device/src/mixer.rs

@@ -0,0 +1,41 @@
+#[derive(Debug, Default)]
+pub enum MixingMode {
+    #[default]
+    Summing,
+    Average,
+}
+
+pub fn mix_summing <const N: usize> (
+    buffer: &mut [Vec<f32>], gain: f32, frames: usize, mut next: impl FnMut()->Option<[f32;N]>,
+) -> bool {
+    let channels = buffer.len();
+    for index in 0..frames {
+        if let Some(frame) = next() {
+            for (channel, sample) in frame.iter().enumerate() {
+                let channel = channel % channels;
+                buffer[channel][index] += sample * gain;
+            }
+        } else {
+            return false
+        }
+    }
+    true
+}
+
+pub fn mix_average <const N: usize> (
+    buffer: &mut [Vec<f32>], gain: f32, frames: usize, mut next: impl FnMut()->Option<[f32;N]>,
+) -> bool {
+    let channels = buffer.len();
+    for index in 0..frames {
+        if let Some(frame) = next() {
+            for (channel, sample) in frame.iter().enumerate() {
+                let channel = channel % channels;
+                let value = buffer[channel][index];
+                buffer[channel][index] = (value + sample * gain) / 2.0;
+            }
+        } else {
+            return false
+        }
+    }
+    true
+}