ADDED: Audio stream processors support -WIP- #2212

This feature is still under consideration/testing and it doesn't work properly, at least the Delay Effect processor.

examples/audio/audio_music_stream.c

@@ -11,6 +11,47 @@
 
 #include "raylib.h"
 
+// Audio effect: lowpass filter
+static void AudioProcessEffectLPF(float *buffer, unsigned int frames)
+{
+    static float low[2] = { 0.0f, 0.0f };
+    static const float cutoff = 70.0f / 44100.0f; // 70 Hz lowpass filter
+    const float k = cutoff / (cutoff + 0.1591549431f); // RC filter formula
+
+    for (unsigned int i = 0; i < frames*2; i += 2)
+    {
+        float l = buffer[i], r = buffer[i + 1];
+        low[0] += k * (l - low[0]);
+        low[1] += k * (r - low[1]);
+        buffer[i] = low[0];
+        buffer[i + 1] = low[1];
+    }
+}
+
+static float *delayBuffer = NULL;
+static unsigned int delayBufferSize = 0;
+static unsigned int delayReadIndex = 2;
+static unsigned int delayWriteIndex = 0;
+
+// Audio effect: delay
+static void AudioProcessEffectDelay(float *buffer, unsigned int frames)
+{
+    for (unsigned int i = 0; i < frames*2; i += 2)
+    {
+        float leftDelay = delayBuffer[delayReadIndex++];    // ERROR: Reading buffer -> WHY??? Maybe thread related???
+        float rightDelay = delayBuffer[delayReadIndex++];
+
+        if (delayReadIndex == delayBufferSize) delayReadIndex = 0;
+
+        buffer[i] = 0.5f*buffer[i] + 0.5f*leftDelay;
+        buffer[i + 1] = 0.5f*buffer[i + 1] + 0.5f*rightDelay;
+
+        delayBuffer[delayWriteIndex++] = buffer[i];
+        delayBuffer[delayWriteIndex++] = buffer[i + 1];
+        if (delayWriteIndex == delayBufferSize) delayWriteIndex = 0;
+    }
+}
+
 int main(void)
 {
     // Initialization
@@ -24,11 +65,17 @@ int main(void)
 
     Music music = LoadMusicStream("resources/country.mp3");
 
+    // Allocate buffer for the delay effect
+    delayBuffer = (float *)RL_CALLOC(48000*2, sizeof(float));   // 1 second delay (device sampleRate*channels)
+
     PlayMusicStream(music);
 
     float timePlayed = 0.0f;
     bool pause = false;
 
+    bool hasFilter = false;
+    bool hasDelay = false;
+
     SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
     //--------------------------------------------------------------------------------------
 
@@ -55,6 +102,22 @@ int main(void)
             else ResumeMusicStream(music);
         }
 
+        // Add/Remove effect: lowpass filter
+        if (IsKeyPressed(KEY_F))
+        {
+            hasFilter = !hasFilter;
+            if (hasFilter) AttachAudioStreamProcessor(music.stream, AudioProcessEffectLPF);
+            else DetachAudioStreamProcessor(music.stream, AudioProcessEffectLPF);
+        }
+
+        // Add/Remove effect: delay
+        if (IsKeyPressed(KEY_D))
+        {
+            hasDelay = !hasDelay;
+            if (hasDelay) AttachAudioStreamProcessor(music.stream, AudioProcessEffectDelay);
+            else DetachAudioStreamProcessor(music.stream, AudioProcessEffectDelay);
+        }
+
         // Get timePlayed scaled to bar dimensions (400 pixels)
         timePlayed = GetMusicTimePlayed(music)/GetMusicTimeLength(music)*400;
 
@@ -86,6 +149,8 @@ int main(void)
 
     CloseAudioDevice();         // Close audio device (music streaming is automatically stopped)
 
+    RL_FREE(delayBuffer);       // Free delay buffer
+
     CloseWindow();              // Close window and OpenGL context
     //--------------------------------------------------------------------------------------