Merge pull request #711 from JerwuQu/jwq_apu-triangle-fix

apu: fix continous tone for triangle
aduros · Apr 20, 2024 · cb6250e · cb6250e
2 parents 60f3947 + 74694d7
commit cb6250e
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Showing 3 changed files with 11 additions and 7 deletions.
diff --git a/runtimes/native/src/apu.c b/runtimes/native/src/apu.c
@@ -5,7 +5,10 @@
 
 #define SAMPLE_RATE 44100
 #define MAX_VOLUME 0x1333 // ~15% of INT16_MAX
+// The triangle channel sounds a bit quieter than the others, so give it higher amplitude
 #define MAX_VOLUME_TRIANGLE 0x2000 // ~25% of INT16_MAX
+// Also the triangle channel prevent popping on hard stops by adding a 1 ms release
+#define RELEASE_TIME_TRIANGLE (SAMPLE_RATE / 1000)
 
 typedef struct {
     /** Starting frequency. */
@@ -97,7 +100,7 @@ static float getCurrentFrequency (const Channel* channel) {
 }
 
 static int16_t getCurrentVolume (const Channel* channel) {
-    if (time >= channel->sustainTime && channel->releaseTime != channel->sustainTime) {
+    if (time >= channel->sustainTime && (channel->releaseTime - channel->sustainTime) > RELEASE_TIME_TRIANGLE) {
         // Release
         return ramp(channel->sustainVolume, 0, channel->sustainTime, channel->releaseTime);
     } else if (time >= channel->decayTime) {
@@ -192,9 +195,8 @@ void w4_apuTone (int frequency, int duration, int volume, int flags) {
         }
 
     } else if (channelIdx == 2) {
-        // For the triangle channel, prevent popping on hard stops by adding a 1 ms release
         if (release == 0) {
-            channel->releaseTime += SAMPLE_RATE/1000;
+            channel->releaseTime += RELEASE_TIME_TRIANGLE;
         }
     }
 }

diff --git a/runtimes/web/src/apu-worklet.ts b/runtimes/web/src/apu-worklet.ts
@@ -3,7 +3,10 @@
 // Audio worklet file: do not export anything directly.
 const SAMPLE_RATE = 44100;
 const MAX_VOLUME = 0.15;
+// The triangle channel sounds a bit quieter than the others, so give it higher amplitude
 const MAX_VOLUME_TRIANGLE = 0.25;
+// Also the triangle channel prevent popping on hard stops by adding a 1 ms release
+const RELEASE_TIME_TRIANGLE = Math.floor(SAMPLE_RATE / 1000);
 
 class Channel {
     /** Starting frequency. */
@@ -114,7 +117,7 @@ class APUProcessor extends AudioWorkletProcessor {
 
     getCurrentVolume (channel: Channel) {
         const time = this.time;
-        if (time >= channel.sustainTime && channel.releaseTime != channel.sustainTime) {
+        if (time >= channel.sustainTime && (channel.releaseTime - channel.sustainTime) > RELEASE_TIME_TRIANGLE) {
             // Release
             return this.ramp(channel.sustainVolume, 0, channel.sustainTime, channel.releaseTime);
         } else if (time >= channel.decayTime) {
@@ -188,9 +191,8 @@ class APUProcessor extends AudioWorkletProcessor {
             }
 
         } else if (channelIdx == 2) {
-            // For the triangle channel, prevent popping on hard stops by adding a 1 ms release
             if (release == 0) {
-                channel.releaseTime += (SAMPLE_RATE/1000) >>> 0;
+                channel.releaseTime += RELEASE_TIME_TRIANGLE;
             }
         }
     }

diff --git a/runtimes/web/src/runtime.ts b/runtimes/web/src/runtime.ts
@@ -334,8 +334,8 @@ export class Runtime {
         let update_function = this.wasm!.exports["update"];
         if (typeof update_function === "function") {
             this.bluescreenOnError(update_function);
-            this.apu.tick();
         }
+        this.apu.tick();
     }
 
     blueScreen (text: string) {