use accurate audio sampling

Author: 39bytes

emu/src/apu/mod.rs

@@ -10,29 +10,29 @@ use serde::{Deserialize, Serialize};
 
 // Precompute lookup tables for sampling
 // See https://www.nesdev.org/wiki/APU_Mixer#Lookup_Table
-const PULSE_TABLE: [f32; 31] = const {
-    let mut pulse_table = [0.0; 31];
-
-    let mut n = 1;
-    while n < 31 {
-        pulse_table[n] = 95.52 / (8128.0 / (n as f32) + 100.0);
-        n += 1;
-    }
-
-    pulse_table
-};
-
-const TND_TABLE: [f32; 203] = const {
-    let mut tnd_table = [0.0; 203];
-
-    let mut n = 1;
-    while n < 203 {
-        tnd_table[n] = 163.67 / (24329.0 / (n as f32) + 100.0);
-        n += 1;
-    }
-
-    tnd_table
-};
+// const PULSE_TABLE: [f32; 31] = const {
+//     let mut pulse_table = [0.0; 31];
+//
+//     let mut n = 1;
+//     while n < 31 {
+//         pulse_table[n] = 95.52 / (8128.0 / (n as f32) + 100.0);
+//         n += 1;
+//     }
+//
+//     pulse_table
+// };
+//
+// const TND_TABLE: [f32; 203] = const {
+//     let mut tnd_table = [0.0; 203];
+//
+//     let mut n = 1;
+//     while n < 203 {
+//         tnd_table[n] = 163.67 / (24329.0 / (n as f32) + 100.0);
+//         n += 1;
+//     }
+//
+//     tnd_table
+// };
 
 #[derive(Clone, Serialize, Deserialize)]
 enum SequenceMode {
@@ -85,28 +85,25 @@ impl Apu {
         // See: https://www.nesdev.org/wiki/APU_Mixer
         let p1 = self.pulse1.sample();
         let p2 = self.pulse2.sample();
-        let pulse_out = PULSE_TABLE[(p1 + p2) as usize];
-        // let pulse_out = match (p1, p2) {
-        //     (0, 0) => 0.0,
-        //     _ => 95.88 / ((8128.0 / (p1 as f32 + p2 as f32)) + 100.0),
-        // };
+        let pulse_out = match (p1, p2) {
+            (0, 0) => 0.0,
+            _ => 95.88 / ((8128.0 / (p1 as f32 + p2 as f32)) + 100.0),
+        };
 
         let triangle = self.triangle.sample();
         let noise = self.noise.sample();
         let dmc = self.dmc.sample();
 
-        let tnd_out = TND_TABLE[(3 * triangle + 2 * noise + dmc) as usize];
-
-        // let tnd_out = match (triangle, noise, dmc) {
-        //     (0, 0, 0) => 0.0,
-        //     _ => {
-        //         let tnd = 1.0
-        //             / ((triangle as f32 / 8227.0)
-        //                 + (noise as f32 / 12241.0)
-        //                 + (dmc as f32 / 22638.0));
-        //         159.79 / (tnd + 100.0)
-        //     }
-        // };
+        let tnd_out = match (triangle, noise, dmc) {
+            (0, 0, 0) => 0.0,
+            _ => {
+                let tnd = 1.0
+                    / ((triangle as f32 / 8227.0)
+                        + (noise as f32 / 12241.0)
+                        + (dmc as f32 / 22638.0));
+                159.79 / (tnd + 100.0)
+            }
+        };
 
         pulse_out + tnd_out
     }