Fix Linux audio: enable JACK support and RT priority for audio callback

Cargo.toml

@@ -53,7 +53,7 @@ doux = { git = "https://github.com/sova-org/doux", features = ["native"] }
 rusty_link = "0.4"
 ratatui = "0.30"
 crossterm = "0.29"
-cpal = "0.17"
+cpal = { version = "0.17", features = ["jack"] }
 clap = { version = "4", features = ["derive"] }
 rand = "0.8"
 serde = { version = "1", features = ["derive"] }

src/engine/audio.rs

@@ -1,4 +1,4 @@
-use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
+use cpal::traits::{DeviceTrait, StreamTrait};
 use cpal::Stream;
 use crossbeam_channel::Receiver;
 use doux::{Engine, EngineMetrics};
@@ -246,14 +246,10 @@ pub fn build_stream(
     initial_samples: Vec<doux::sampling::SampleEntry>,
     audio_sample_pos: Arc<AtomicU64>,
 ) -> Result<(Stream, f32, AnalysisHandle), String> {
-    let host = cpal::default_host();
-
     let device = match &config.output_device {
         Some(name) => doux::audio::find_output_device(name)
             .ok_or_else(|| format!("Device not found: {name}"))?,
-        None => host
-            .default_output_device()
-            .ok_or("No default output device")?,
+        None => doux::audio::default_output_device().ok_or("No default output device")?,
     };
 
     let default_config = device.default_output_config().map_err(|e| e.to_string())?;
@@ -282,11 +278,17 @@ pub fn build_stream(
     let (mut fft_producer, analysis_handle) = spawn_analysis_thread(sample_rate, spectrum_buffer);
 
     let mut cmd_buffer = String::with_capacity(256);
+    let mut rt_set = false;
 
     let stream = device
         .build_output_stream(
             &stream_config,
             move |data: &mut [f32], _| {
+                if !rt_set {
+                    super::realtime::set_realtime_priority();
+                    rt_set = true;
+                }
+
                 let buffer_samples = data.len() / channels;
                 let buffer_time_ns = (buffer_samples as f64 / sr as f64 * 1e9) as u64;