feat(autodj): smooth skip and interrupt blend transitions (#1128)

src-tauri/crates/psysonic-audio/src/commands.rs

@@ -72,6 +72,9 @@ pub async fn audio_play(
     // while B rises underneath); `Some(x)` → fade A over x s; `None` → mirror
     // B's fade (today's behaviour). Always clamped to A's measured remaining.
     outgoing_fade_secs_override: Option<f32>,
+    // AutoDJ smooth skip: short outgoing fade when the user hits next/previous
+    // while a track is playing. Optional; only honoured when `manual` is true.
+    manual_autodj_blend: Option<bool>,
     app: AppHandle,
     state: State<'_, AudioEngine>,
 ) -> Result<(), String> {
@@ -236,8 +239,10 @@ pub async fn audio_play(
         },
     );
 
-    // Manual skips (user-initiated) bypass crossfade — the track should start immediately.
-    let crossfade_enabled = state.crossfade_enabled.load(Ordering::Relaxed) && !manual;
+    // Manual skips bypass crossfade unless AutoDJ smooth skip requests a full blend.
+    let manual_blend = manual && manual_autodj_blend.unwrap_or(false);
+    let crossfade_enabled =
+        state.crossfade_enabled.load(Ordering::Relaxed) && (!manual || manual_blend);
     // Per-transition override (dynamic crossfade) caps the fade for this swap;
     // otherwise fall back to the global crossfade length. Both clamped the same.
     let crossfade_secs_val = crossfade_secs_override

src-tauri/crates/psysonic-audio/src/engine.rs

@@ -66,6 +66,9 @@ pub struct AudioEngine {
     /// the engine from starting a still-buffering next track and fading over it
     /// (an audible "jump"); cold next-track degrades to a clean sequential start.
     pub(crate) autodj_suppress_autocrossfade: Arc<AtomicBool>,
+    /// AutoDJ interrupt prep: `audio_begin_outgoing_fade` volume-ducked the
+    /// outgoing sink; block normalization/volume ramps until the handoff swap.
+    pub(crate) interrupt_outgoing_duck_active: Arc<AtomicBool>,
     pub fading_out_sink: Arc<Mutex<Option<Arc<Player>>>>,
     /// When true, audio_play chains sources to the existing Sink instead of
     /// creating a new one, achieving sample-accurate gapless transitions.
@@ -482,6 +485,7 @@ pub fn create_engine() -> (AudioEngine, std::thread::JoinHandle<()>) {
         crossfade_enabled: Arc::new(AtomicBool::new(false)),
         crossfade_secs: Arc::new(AtomicU32::new(3.0f32.to_bits())),
         autodj_suppress_autocrossfade: Arc::new(AtomicBool::new(false)),
+        interrupt_outgoing_duck_active: Arc::new(AtomicBool::new(false)),
         fading_out_sink: Arc::new(Mutex::new(None)),
         gapless_enabled: Arc::new(AtomicBool::new(false)),
         normalization_engine: Arc::new(AtomicU32::new(0)),

src-tauri/crates/psysonic-audio/src/helpers.rs

@@ -805,6 +805,19 @@ pub(crate) fn loudness_ui_current_gain_db(gain_linear: f32) -> Option<f32> {
     gain_linear_to_db(gain_linear)
 }
 
+static SINK_VOLUME_RAMP_GEN: AtomicU64 = AtomicU64::new(0);
+
+/// Cancel any in-flight sink-volume ramp (new ramp wins).
+pub(crate) fn cancel_sink_volume_ramp() {
+    SINK_VOLUME_RAMP_GEN.fetch_add(1, Ordering::SeqCst);
+}
+
+/// Audible sink multiplier — may differ from `base_volume * replay_gain` after
+/// interrupt prep or a mid-ramp correction.
+pub(crate) fn sink_volume_now(sink: &Player) -> f32 {
+    sink.volume().clamp(0.0, 1.0)
+}
+
 pub(crate) fn ramp_sink_volume(sink: Arc<Player>, from: f32, to: f32) {
     let from = from.clamp(0.0, 1.0);
     let to = to.clamp(0.0, 1.0);
@@ -812,8 +825,7 @@ pub(crate) fn ramp_sink_volume(sink: Arc<Player>, from: f32, to: f32) {
         sink.set_volume(to);
         return;
     }
-    static RAMP_GEN: AtomicU64 = AtomicU64::new(0);
-    let my_gen = RAMP_GEN.fetch_add(1, Ordering::SeqCst) + 1;
+    let my_gen = SINK_VOLUME_RAMP_GEN.fetch_add(1, Ordering::SeqCst) + 1;
     std::thread::spawn(move || {
         let delta = (to - from).abs();
         // Stretch large corrections to avoid audible "step down" moments.
@@ -826,18 +838,46 @@ pub(crate) fn ramp_sink_volume(sink: Arc<Player>, from: f32, to: f32) {
         } else {
             (8, 16)
         };
-        for i in 1..=steps {
-            if RAMP_GEN.load(Ordering::SeqCst) != my_gen {
-                return;
-            }
-            let t = i as f32 / steps as f32;
-            let v = from + (to - from) * t;
-            sink.set_volume(v.clamp(0.0, 1.0));
-            std::thread::sleep(Duration::from_millis(step_ms));
-        }
+        ramp_sink_volume_steps(sink, from, to, steps, step_ms, my_gen);
     });
 }
 
+/// Linear sink-volume ramp over an explicit wall-clock duration (interrupt prep).
+pub(crate) fn ramp_sink_volume_over_secs(sink: Arc<Player>, from: f32, to: f32, secs: f32) {
+    let from = from.clamp(0.0, 1.0);
+    let to = to.clamp(0.0, 1.0);
+    if (to - from).abs() < 0.002 {
+        sink.set_volume(to);
+        return;
+    }
+    let my_gen = SINK_VOLUME_RAMP_GEN.fetch_add(1, Ordering::SeqCst) + 1;
+    let secs = secs.clamp(0.1, 12.0);
+    let step_ms: u64 = 20;
+    let steps = ((secs * 1000.0) / step_ms as f32).round().max(1.0) as usize;
+    std::thread::spawn(move || {
+        ramp_sink_volume_steps(sink, from, to, steps, step_ms, my_gen);
+    });
+}
+
+fn ramp_sink_volume_steps(
+    sink: Arc<Player>,
+    from: f32,
+    to: f32,
+    steps: usize,
+    step_ms: u64,
+    my_gen: u64,
+) {
+    for i in 1..=steps {
+        if SINK_VOLUME_RAMP_GEN.load(Ordering::SeqCst) != my_gen {
+            return;
+        }
+        let t = i as f32 / steps as f32;
+        let v = from + (to - from) * t;
+        sink.set_volume(v.clamp(0.0, 1.0));
+        std::thread::sleep(Duration::from_millis(step_ms));
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src-tauri/crates/psysonic-audio/src/mix_commands.rs

@@ -13,9 +13,9 @@ use super::ipc::{maybe_emit_normalization_state, NormalizationStatePayload};
 #[tauri::command]
 pub fn audio_set_volume(volume: f32, state: State<'_, AudioEngine>) {
     let mut cur = state.current.lock().unwrap();
-    let prev_effective = (cur.base_volume * cur.replay_gain_linear * MASTER_HEADROOM).clamp(0.0, 1.0);
     cur.base_volume = volume.clamp(0.0, 1.0);
     if let Some(sink) = &cur.sink {
+        let prev_effective = sink_volume_now(sink);
         let next_effective = (cur.base_volume * cur.replay_gain_linear * MASTER_HEADROOM).clamp(0.0, 1.0);
         ramp_sink_volume(Arc::clone(sink), prev_effective, next_effective);
     }
@@ -105,11 +105,19 @@ pub fn audio_update_replay_gain(
         volume,
         effective
     );
+    if state
+        .interrupt_outgoing_duck_active
+        .load(Ordering::Relaxed)
+    {
+        // Interrupt prep ducked the outgoing sink; syncing B's loudness here would
+        // ramp A back to full gain before the handoff swap.
+        return;
+    }
     let mut cur = state.current.lock().unwrap();
-    let prev_effective = (cur.base_volume * cur.replay_gain_linear * MASTER_HEADROOM).clamp(0.0, 1.0);
     cur.replay_gain_linear = gain_linear;
     cur.base_volume = volume.clamp(0.0, 1.0);
     if let Some(sink) = &cur.sink {
+        let prev_effective = sink_volume_now(sink);
         ramp_sink_volume(Arc::clone(sink), prev_effective, effective);
     }
     drop(cur);
@@ -143,6 +151,23 @@ pub fn audio_set_gapless(enabled: bool, state: State<'_, AudioEngine>) {
     state.gapless_enabled.store(enabled, Ordering::Relaxed);
 }
 
+/// Duck the current sink over `fade_secs` without exhausting its source (which
+/// would spuriously emit `audio:ended` before the interrupt handoff).
+#[tauri::command]
+pub fn audio_begin_outgoing_fade(fade_secs: f32, state: State<'_, AudioEngine>) {
+    let fade_secs = fade_secs.clamp(0.1, 12.0);
+    let cur = state.current.lock().unwrap();
+    let Some(sink) = cur.sink.as_ref() else {
+        return;
+    };
+    state
+        .interrupt_outgoing_duck_active
+        .store(true, Ordering::Relaxed);
+    cancel_sink_volume_ramp();
+    let from = sink_volume_now(sink);
+    ramp_sink_volume_over_secs(Arc::clone(sink), from, 0.0, fade_secs);
+}
+
 /// AutoDJ: when `true`, the progress task stops firing its autonomous
 /// crossfade `audio:ended` timer so the JS A-tail logic drives every advance
 /// (only when the next track is actually playable). When `false`, the engine's

src-tauri/crates/psysonic-audio/src/sink_swap.rs

@@ -96,6 +96,43 @@ pub(crate) struct SinkSwapInputs {
     pub(crate) start_paused: bool,
 }
 
+/// Hand off the outgoing sink to a sample-level fade-out, then stop it after
+/// `cleanup_secs`. No-op when `fade_secs <= 0` (immediate stop).
+fn handoff_old_sink_fade_out(
+    state: &State<'_, AudioEngine>,
+    old_sink: Option<Arc<rodio::Player>>,
+    old_fadeout_trigger: Option<Arc<AtomicBool>>,
+    old_fadeout_samples: Option<Arc<AtomicU64>>,
+    fade_secs: f32,
+    cleanup_secs: f32,
+) {
+    let Some(old) = old_sink else {
+        return;
+    };
+    if fade_secs <= 0.0 {
+        old.stop();
+        return;
+    }
+    let rate = state.current_sample_rate.load(Ordering::Relaxed);
+    let ch = state.current_channels.load(Ordering::Relaxed);
+    let fade_total = (fade_secs as f64 * rate as f64 * ch as f64) as u64;
+
+    if let (Some(trigger), Some(samples)) = (old_fadeout_trigger, old_fadeout_samples) {
+        samples.store(fade_total.max(1), Ordering::SeqCst);
+        trigger.store(true, Ordering::SeqCst);
+    }
+
+    *state.fading_out_sink.lock().unwrap() = Some(old);
+    let fo_arc = state.fading_out_sink.clone();
+    let cleanup_dur = Duration::from_secs_f32(cleanup_secs.max(fade_secs + 0.1));
+    tokio::spawn(async move {
+        tokio::time::sleep(cleanup_dur).await;
+        if let Some(s) = fo_arc.lock().unwrap().take() {
+            s.stop();
+        }
+    });
+}
+
 /// Atomically swap the new sink into `state.current`, then handle the old
 /// sink: trigger sample-level fade-out (crossfade enabled) or stop it
 /// immediately (hard cut). The fade-out is handed off to a small spawned
@@ -138,30 +175,29 @@ pub(crate) fn swap_in_new_sink(state: &State<'_, AudioEngine>, inputs: SinkSwapI
     };
 
     if crossfade_enabled {
-        if let Some(old) = old_sink {
-            // Trigger sample-level fade-out on Track A via TriggeredFadeOut —
-            // unless `outgoing_fade_secs` is 0 (scenario A): then A keeps full
-            // engine gain and its own recorded fade carries it down while B
-            // rises underneath. Either way the old sink is kept alive until B's
-            // fade-in window elapses, so A plays out its tail before being
-            // dropped.
-            if outgoing_fade_secs > 0.0 {
-                let rate = state.current_sample_rate.load(Ordering::Relaxed);
-                let ch = state.current_channels.load(Ordering::Relaxed);
-                let fade_total = (outgoing_fade_secs as f64 * rate as f64 * ch as f64) as u64;
-
-                if let (Some(trigger), Some(samples)) = (old_fadeout_trigger, old_fadeout_samples) {
-                    samples.store(fade_total.max(1), Ordering::SeqCst);
-                    trigger.store(true, Ordering::SeqCst);
-                }
+        if outgoing_fade_secs > 0.0 {
+            // Scenario A (`outgoing_fade_secs == 0`): A keeps full engine gain;
+            // still keep the old sink alive until B's fade-in window elapses.
+            handoff_old_sink_fade_out(
+                state,
+                old_sink,
+                old_fadeout_trigger,
+                old_fadeout_samples,
+                outgoing_fade_secs,
+                actual_fade_secs.max(outgoing_fade_secs) + 0.5,
+            );
+        } else if let Some(old) = old_sink {
+            // Prep already volume-ducked A; scenario-A keeps sample gain at 1.0
+            // so clamp the handoff sink or A blasts over B's fade-in.
+            if state
+                .interrupt_outgoing_duck_active
+                .load(Ordering::Relaxed)
+            {
+                old.set_volume(0.0);
             }
-
-            // Keep old sink alive until the fade completes + small margin,
-            // then drop it. No volume stepping needed — the fade-out runs
-            // at sample level inside the audio thread.
             *state.fading_out_sink.lock().unwrap() = Some(old);
             let fo_arc = state.fading_out_sink.clone();
-            let cleanup_dur = Duration::from_secs_f32(actual_fade_secs.max(outgoing_fade_secs) + 0.5);
+            let cleanup_dur = Duration::from_secs_f32(actual_fade_secs + 0.5);
             tokio::spawn(async move {
                 tokio::time::sleep(cleanup_dur).await;
                 if let Some(s) = fo_arc.lock().unwrap().take() {
@@ -172,4 +208,7 @@ pub(crate) fn swap_in_new_sink(state: &State<'_, AudioEngine>, inputs: SinkSwapI
     } else if let Some(old) = old_sink {
         old.stop();
     }
+    state
+        .interrupt_outgoing_duck_active
+        .store(false, Ordering::Relaxed);
 }

src-tauri/crates/psysonic-audio/src/stream_idle.rs

@@ -205,6 +205,7 @@ mod tests {
             crossfade_enabled: Arc::new(AtomicBool::new(false)),
             crossfade_secs: Arc::new(AtomicU32::new(0)),
             autodj_suppress_autocrossfade: Arc::new(AtomicBool::new(false)),
+            interrupt_outgoing_duck_active: Arc::new(AtomicBool::new(false)),
             fading_out_sink: Arc::new(Mutex::new(None)),
             gapless_enabled: Arc::new(AtomicBool::new(false)),
             normalization_engine: Arc::new(AtomicU32::new(0)),