Initial release: real-time voice changer in pure Rust

Phase-vocoder pitch/formant shifting, 12 presets, effect chain,
noise gate, WAV recording, full-screen TUI (arrow/mouse control)
and a built-in PipeWire/PulseAudio virtual mic (vois.rs).
GPL-3.0-or-later.

src/audio/capture.rs

@@ -0,0 +1,69 @@
+use anyhow::{Context, Result};
+use cpal::traits::{DeviceTrait, HostTrait};
+use cpal::{
+    Device, FromSample, Host, Sample, SampleFormat, SizedSample, Stream, StreamConfig,
+    SupportedStreamConfig,
+};
+use ringbuf::traits::Producer;
+
+pub fn find_input(host: &Host, name: Option<&str>) -> Result<Device> {
+    match name {
+        Some(name) => host
+            .input_devices()
+            .context("failed to enumerate input devices")?
+            .find(|d| d.name().map(|n| n == name).unwrap_or(false))
+            .with_context(|| format!("input device {name:?} not found")),
+        None => host
+            .default_input_device()
+            .context("no default input device found"),
+    }
+}
+
+/// Open the input stream. Captured samples are converted to `f32` (interleaved
+/// frames) and pushed into `tx`.
+pub fn start<P>(device: &Device, supported: &SupportedStreamConfig, tx: P) -> Result<Stream>
+where
+    P: Producer<Item = f32> + Send + 'static,
+{
+    let config: StreamConfig = supported.config();
+    match supported.sample_format() {
+        SampleFormat::F32 => build::<f32, P>(device, &config, tx),
+        SampleFormat::F64 => build::<f64, P>(device, &config, tx),
+        SampleFormat::I8 => build::<i8, P>(device, &config, tx),
+        SampleFormat::I16 => build::<i16, P>(device, &config, tx),
+        SampleFormat::I32 => build::<i32, P>(device, &config, tx),
+        SampleFormat::I64 => build::<i64, P>(device, &config, tx),
+        SampleFormat::U8 => build::<u8, P>(device, &config, tx),
+        SampleFormat::U16 => build::<u16, P>(device, &config, tx),
+        SampleFormat::U32 => build::<u32, P>(device, &config, tx),
+        SampleFormat::U64 => build::<u64, P>(device, &config, tx),
+        format => anyhow::bail!("unsupported input sample format: {format:?}"),
+    }
+}
+
+fn build<T, P>(device: &Device, config: &StreamConfig, mut tx: P) -> Result<Stream>
+where
+    T: SizedSample,
+    f32: FromSample<T>,
+    P: Producer<Item = f32> + Send + 'static,
+{
+    let channels = config.channels as usize;
+    let mut frame = vec![0f32; channels];
+    let err_fn = |err| eprintln!("capture stream error: {err}");
+
+    device
+        .build_input_stream(
+            config,
+            move |data: &[T], _: &cpal::InputCallbackInfo| {
+                for chunk in data.chunks(channels) {
+                    for (slot, sample) in frame.iter_mut().zip(chunk) {
+                        *slot = f32::from_sample(*sample);
+                    }
+                    let _ = tx.push_slice(&frame);
+                }
+            },
+            err_fn,
+            None,
+        )
+        .map_err(|e| anyhow::anyhow!("failed to build input stream: {e}"))
+}