fix: shared oversampling control with race condition fixes (#227)

Author: OpenSauce

presets/High_Gain.json

@@ -3,63 +3,127 @@
   "description": null,
   "author": null,
   "stages": [
+    {
+      "NoiseGate": {
+        "threshold_db": -40.0,
+        "ratio": 10.0,
+        "attack_ms": 0.5,
+        "hold_ms": 80.0,
+        "release_ms": 150.0,
+        "bypassed": false
+      }
+    },
     {
       "Preamp": {
-        "gain": 6.7000003,
-        "bias": 0.0,
-        "clipper_type": "ClassA"
+        "gain": 3.5,
+        "bias": 0.05,
+        "clipper_type": "Triode",
+        "bypassed": false
       }
     },
     {
-      "ToneStack": {
-        "model": "British",
-        "bass": 0.75,
-        "mid": 1.0,
-        "treble": 0.95,
-        "presence": 0.65000004
+      "Preamp": {
+        "gain": 5.2000003,
+        "bias": 0.40000004,
+        "clipper_type": "Triode",
+        "bypassed": false
       }
     },
     {
-      "Compressor": {
-        "attack_ms": 1.0,
-        "release_ms": 80.0,
-        "threshold_db": -16.0,
-        "ratio": 4.0,
-        "makeup_db": 16.7
+      "Preamp": {
+        "gain": 4.2,
+        "bias": -0.1,
+        "clipper_type": "Triode",
+        "bypassed": false
       }
     },
     {
       "Preamp": {
-        "gain": 6.8,
-        "bias": 1.4901161e-08,
-        "clipper_type": "Hard"
+        "gain": 5.0,
+        "bias": 0.15,
+        "clipper_type": "Triode",
+        "bypassed": false
       }
     },
     {
-      "Level": {
-        "gain": 0.5
+      "Preamp": {
+        "gain": 5.8,
+        "bias": -0.05,
+        "clipper_type": "Triode",
+        "bypassed": false
       }
     },
     {
-      "NoiseGate": {
-        "threshold_db": -13.0,
-        "ratio": 10.0,
-        "attack_ms": 3.7,
-        "hold_ms": 10.0,
-        "release_ms": 100.0
+      "ToneStack": {
+        "model": "American",
+        "bass": 0.90000004,
+        "mid": 1.0,
+        "treble": 1.0,
+        "presence": 0.65000004,
+        "bypassed": false
+      }
+    },
+    {
+      "PowerAmp": {
+        "drive": 0.15,
+        "amp_type": "ClassAB",
+        "sag": 0.3,
+        "sag_release": 120.0,
+        "bypassed": false
+      }
+    },
+    {
+      "MultibandSaturator": {
+        "low_drive": 0.06,
+        "mid_drive": 0.16,
+        "high_drive": 0.099999994,
+        "low_level": 0.72999996,
+        "mid_level": 0.87,
+        "high_level": 0.84,
+        "low_freq": 347.0,
+        "high_freq": 2810.0,
+        "bypassed": false
+      }
+    },
+    {
+      "Eq": {
+        "gains": [
+          -7.7999997,
+          -5.9,
+          -3.1999998,
+          -3.4999998,
+          -1.9999999,
+          -1.0999998,
+          -0.09999982,
+          0.5000002,
+          0.0,
+          -1.5999999,
+          1.7881393e-7,
+          -0.79999983,
+          0.0,
+          -1.5999999,
+          -2.6999998,
+          -3.4999998
+        ],
+        "bypassed": false
       }
     },
     {
-      "Level": {
-        "gain": 1.0
+      "Reverb": {
+        "room_size": 0.22,
+        "damping": 0.72999996,
+        "mix": 0.2,
+        "bypassed": false
       }
     }
   ],
-  "ir_name": "Jesterdyne/Engl/sc450-left-01.wav",
+  "ir_name": "Science Amplification/4x12/G12H-150/SM57 Darker.wav",
+  "ir_gain": 0.21,
+  "pitch_shift_semitones": 0,
   "input_filters": {
     "hp_enabled": true,
-    "hp_cutoff": 187.0,
+    "hp_cutoff": 80.0,
     "lp_enabled": true,
-    "lp_cutoff": 9913.0
+    "lp_cutoff": 9000.0
   }
-}
+}

rustortion-plugin/src/backend.rs

@@ -20,7 +20,6 @@ pub struct PluginBackend {
     shared_state: Arc<SharedState>,
     capabilities: Capabilities,
     sample_rate: f32,
-    oversampling_factor: u32,
 }
 
 impl PluginBackend {
@@ -31,7 +30,6 @@ impl PluginBackend {
         ir_loader: Option<Arc<IrLoader>>,
         shared_state: Arc<SharedState>,
         sample_rate: f32,
-        oversampling_factor: u32,
     ) -> Self {
         Self {
             engine_handle,
@@ -41,7 +39,6 @@ impl PluginBackend {
             shared_state,
             capabilities: Capabilities::plugin(),
             sample_rate,
-            oversampling_factor,
         }
     }
 
@@ -50,9 +47,16 @@ impl PluginBackend {
         self.params.chain_state.lock().ok()?.clone()
     }
 
+    /// Effective sample rate using the *active* (applied) oversampling factor,
+    /// not the requested one. This ensures chain rebuilds match the current
+    /// sampler state.
     #[allow(clippy::cast_precision_loss)]
     fn effective_sample_rate(&self) -> f32 {
-        self.sample_rate * self.oversampling_factor as f32
+        let active = self
+            .shared_state
+            .active_oversampling
+            .load(std::sync::atomic::Ordering::Relaxed);
+        self.sample_rate * active as f32
     }
 
     /// Notify the host that a parameter value changed from the GUI.
@@ -187,10 +191,23 @@ impl ParamBackend for PluginBackend {
         self.notify_host_param_changed(param.as_ptr(), param.preview_normalized(idx));
     }
 
-    fn set_oversampling(&self, _factor: u32) {
-        // Oversampling changes in plugin mode are handled through the
-        // nih-plug parameter system and the process() loop. This trait
-        // method is a no-op for the plugin backend.
+    fn set_oversampling(&self, factor: u32) {
+        debug_assert!(
+            factor.is_power_of_two() && factor > 0 && factor <= 16,
+            "oversampling factor must be a power of two in [1, 16], got {factor}"
+        );
+        self.shared_state
+            .requested_oversampling
+            .store(factor, std::sync::atomic::Ordering::Relaxed);
+        // Sync to params for DAW project persistence
+        self.params
+            .oversampling_factor
+            .store(factor, std::sync::atomic::Ordering::Relaxed);
+        // Mark DAW session dirty so the new value is saved with the project.
+        // #[persist] fields are serialized passively and don't trigger a save.
+        let param = &self.params.preset_idx;
+        let current = param.modulated_normalized_value();
+        self.notify_host_param_changed(param.as_ptr(), current);
     }
 
     fn sample_rate(&self) -> u32 {
@@ -200,7 +217,9 @@ impl ParamBackend for PluginBackend {
     }
 
     fn oversampling_factor(&self) -> u32 {
-        self.oversampling_factor
+        self.shared_state
+            .requested_oversampling
+            .load(std::sync::atomic::Ordering::Relaxed)
     }
 
     fn capabilities(&self) -> &Capabilities {

rustortion-plugin/src/editor.rs

@@ -79,12 +79,6 @@ impl Editor for PluginEditor {
                 .sample_rate
                 .load(std::sync::atomic::Ordering::Relaxed),
         );
-        let os_idx = self
-            .shared_state
-            .oversampling_idx
-            .load(std::sync::atomic::Ordering::Relaxed);
-        let oversampling_factor = 2_u32.pow(u32::from(os_idx));
-
         let restored_preset_idx = self.params.preset_idx.value();
 
         let flags = PluginAppFlags {
@@ -94,7 +88,6 @@ impl Editor for PluginEditor {
             engine_handle,
             ir_loader,
             sample_rate,
-            oversampling_factor,
             restored_preset_idx,
         };
 
@@ -145,7 +138,6 @@ struct PluginAppFlags {
     engine_handle: Option<rustortion_core::audio::engine::EngineHandle>,
     ir_loader: Option<Arc<rustortion_core::ir::loader::IrLoader>>,
     sample_rate: f32,
-    oversampling_factor: u32,
     restored_preset_idx: i32,
 }
 
@@ -172,7 +164,6 @@ impl iced_baseview::Application for PluginApp {
             flags.ir_loader,
             flags.shared_state.clone(),
             flags.sample_rate,
-            flags.oversampling_factor,
         );
 
         let available_irs = backend.get_available_irs();
@@ -209,6 +200,7 @@ impl iced_baseview::Application for PluginApp {
             preset_handler.load_preset_by_name(name);
         }
 
+        let oversampling_factor = backend.oversampling_factor();
         let shared = SharedApp {
             backend,
             stages: Vec::new(),
@@ -222,6 +214,7 @@ impl iced_baseview::Application for PluginApp {
             peak_meter_display: PeakMeterDisplay::default(),
             hotkey_handler: HotkeyHandler::new(HotkeySettings::default()),
             input_filter_config: rustortion_core::preset::InputFilterConfig::default(),
+            oversampling_factor,
             is_recording: false,
         };