PannerNode: cache the entire HRTFProcessor (not just the HRIR sphere)

This reduces panner node HRTF setting time to ~1ms

Author: orottier

src/node/panner.rs

@@ -15,20 +15,27 @@ use super::{
     AudioNode, ChannelConfig, ChannelConfigOptions, ChannelCountMode, ChannelInterpretation,
 };
 
-/// Load the HRIR sphere for the given sample_rate
+/// Load the HRTF processor for the given sample_rate
 ///
 /// The included data contains the impulse responses at 44100 Hertz, so it needs to be resampled
 /// for other values (which can easily take 100s of milliseconds). Therefore cache the result (per
 /// sample rate) in a global variable and clone it every time a new panner is created.
-fn load_hrir_sphere(sample_rate: u32) -> HrirSphere {
-    static INSTANCE: OnceLock<Mutex<HashMap<u32, HrirSphere>>> = OnceLock::new();
+fn load_hrtf_processor(sample_rate: u32) -> (HrtfProcessor, usize) {
+    static INSTANCE: OnceLock<Mutex<HashMap<u32, (HrtfProcessor, usize)>>> = OnceLock::new();
     let cache = INSTANCE.get_or_init(|| Mutex::new(HashMap::new()));
     let mut guard = cache.lock().unwrap();
     guard
         .entry(sample_rate)
         .or_insert_with(|| {
             let resource = include_bytes!("../../resources/IRC_1003_C.bin");
-            HrirSphere::new(&resource[..], sample_rate).unwrap()
+            let hrir_sphere = HrirSphere::new(&resource[..], sample_rate).unwrap();
+            let len = hrir_sphere.len();
+
+            let interpolation_steps = 1; // TODO?
+            let samples_per_step = RENDER_QUANTUM_SIZE / interpolation_steps;
+            let processor = HrtfProcessor::new(hrir_sphere, interpolation_steps, samples_per_step);
+
+            (processor, len)
         })
         .clone()
 }
@@ -187,14 +194,7 @@ struct HrtfState {
 }
 
 impl HrtfState {
-    fn new(hrir_sphere: HrirSphere) -> Self {
-        let len = hrir_sphere.len();
-
-        let interpolation_steps = 1;
-        let samples_per_step = RENDER_QUANTUM_SIZE / interpolation_steps;
-
-        let processor = HrtfProcessor::new(hrir_sphere, interpolation_steps, samples_per_step);
-
+    fn new(processor: HrtfProcessor, len: usize) -> Self {
         Self {
             len,
             processor,
@@ -570,8 +570,8 @@ impl PannerNode {
             PanningModelType::EqualPower => None,
             PanningModelType::HRTF => {
                 let sample_rate = self.context().sample_rate() as u32;
-                let hrir_sphere = load_hrir_sphere(sample_rate);
-                Some(HrtfState::new(hrir_sphere))
+                let (processor, len) = load_hrtf_processor(sample_rate);
+                Some(HrtfState::new(processor, len))
             }
         };