Add audio processors to the streams system.

examples/audio/audio_music_stream.c

@@ -14,6 +14,23 @@
 
 #define AUDIO_THREAD_MUSIC_UPDATE true
 
+// a simple lowpass filter applied to the music stream
+static void audioEffectDemo(float* buffer, unsigned int nframes)
+{
+    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 < nframes*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];
+    }
+}
+
 int main(void)
 {
     // Initialization
@@ -32,6 +49,7 @@ int main(void)
 
     float timePlayed = 0.0f;
     bool pause = false;
+    bool hasfx = false;
 
     SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
     //--------------------------------------------------------------------------------------
@@ -62,6 +80,20 @@ int main(void)
             else ResumeMusicStream(music);
         }
 
+        // Add/Remove effect
+        if (IsKeyPressed(KEY_F))
+        {
+            hasfx = !hasfx;
+            if (hasfx)
+            {
+                AddAudioStreamProcessor(music.stream, &audioEffectDemo);
+            }
+            else
+            {
+                RemoveAudioStreamProcessor(music.stream, &audioEffectDemo);
+            }
+        }
+
         // Get timePlayed scaled to bar dimensions (400 pixels)
         timePlayed = GetMusicTimePlayed(music)/GetMusicTimeLength(music)*400;
 
@@ -79,9 +111,11 @@ int main(void)
             DrawRectangle(200, 200, 400, 12, LIGHTGRAY);
             DrawRectangle(200, 200, (int)timePlayed, 12, MAROON);
             DrawRectangleLines(200, 200, 400, 12, GRAY);
+            DrawRectangleLines(200, 200, 400, 12, GRAY);
 
             DrawText("PRESS SPACE TO RESTART MUSIC", 215, 250, 20, LIGHTGRAY);
             DrawText("PRESS P TO PAUSE/RESUME MUSIC", 208, 280, 20, LIGHTGRAY);
+            DrawText("PRESS F TO ADD/REMOVE EFFECT", 208, 310, 20, LIGHTGRAY);
 
         EndDrawing();
         //----------------------------------------------------------------------------------

src/raudio.c

@@ -311,12 +311,22 @@ typedef enum {
     AUDIO_BUFFER_USAGE_STREAM
 } AudioBufferUsage;
 
+
+// Audio processor - to apply effects to an AudioBuffer
+struct rAudioProcessor {
+    void (*process)(float*, unsigned int);
+    rAudioProcessor *next;
+    rAudioProcessor *prev;
+};
+
+
 // Audio buffer structure
 struct rAudioBuffer {
     ma_data_converter converter;    // Audio data converter
 
-    void (*audioCallback)(void*, unsigned int); // optional callback for filling in buffer on audio threads
+    void (*audioCallback)(void*, unsigned int, void*); // optional callback for filling in buffer on audio threads
     void* audioCallbackData;        // optional data passed to callback
+    rAudioProcessor* processor;
 
     float volume;                   // Audio buffer volume
     float pitch;                    // Audio buffer pitch
@@ -349,7 +359,6 @@ typedef struct AudioData {
     } System;
     struct {
         AudioBuffer *first;         // Pointer to first AudioBuffer in the list
-        AudioBuffer *last;          // Pointer to last AudioBuffer in the list
         int defaultSize;            // Default audio buffer size for audio streams
     } Buffer;
     struct {
@@ -399,7 +408,7 @@ void PlayAudioBuffer(AudioBuffer *buffer);
 void StopAudioBuffer(AudioBuffer *buffer);
 void PauseAudioBuffer(AudioBuffer *buffer);
 void ResumeAudioBuffer(AudioBuffer *buffer);
-void SetAudioBufferCallback(AudioBuffer* buffer, int callback(void*));
+void SetAudioBufferCallback(AudioBuffer* buffer, void callback(void*, unsigned int, void*), void*);
 void SetAudioBufferVolume(AudioBuffer *buffer, float volume);
 void SetAudioBufferPitch(AudioBuffer *buffer, float pitch);
 void TrackAudioBuffer(AudioBuffer *buffer);
@@ -532,7 +541,6 @@ void SetMasterVolume(float volume)
 AudioBuffer *LoadAudioBuffer(ma_format format, ma_uint32 channels, ma_uint32 sampleRate, ma_uint32 sizeInFrames, int usage)
 {
     AudioBuffer *audioBuffer = (AudioBuffer *)RL_CALLOC(1, sizeof(AudioBuffer));
-
     if (audioBuffer == NULL)
     {
         TRACELOG(LOG_WARNING, "AUDIO: Failed to allocate memory for buffer");
@@ -559,6 +567,7 @@ AudioBuffer *LoadAudioBuffer(ma_format format, ma_uint32 channels, ma_uint32 sam
     audioBuffer->pitch = 1.0f;
     audioBuffer->audioCallback = NULL;
     audioBuffer->audioCallbackData = NULL;
+    audioBuffer->processor = NULL;
     audioBuffer->playing = false;
     audioBuffer->paused = false;
     audioBuffer->looping = false;
@@ -679,14 +688,10 @@ void TrackAudioBuffer(AudioBuffer *buffer)
 {
     ma_mutex_lock(&AUDIO.System.lock);
     {
-        if (AUDIO.Buffer.first == NULL) AUDIO.Buffer.first = buffer;
+        AudioBuffer* old = AUDIO.Buffer.first;
-        else
+        buffer->next = old;
-        {
+        if (old) old->prev = buffer;
-            AUDIO.Buffer.last->next = buffer;
+        AUDIO.Buffer.first = buffer;
-            buffer->prev = AUDIO.Buffer.last;
-        }
-
-        AUDIO.Buffer.last = buffer;
     }
     ma_mutex_unlock(&AUDIO.System.lock);
 }
@@ -696,11 +701,11 @@ void UntrackAudioBuffer(AudioBuffer *buffer)
 {
     ma_mutex_lock(&AUDIO.System.lock);
     {
-        if (buffer->prev == NULL) AUDIO.Buffer.first = buffer->next;
+        AudioBuffer* p = buffer->prev;
-        else buffer->prev->next = buffer->next;
+        AudioBuffer* n = buffer->next;
-
+        if (p) p->next = n;
-        if (buffer->next == NULL) AUDIO.Buffer.last = buffer->prev;
+        if (n) n->prev = p;
-        else buffer->next->prev = buffer->prev;
+        if (buffer == AUDIO.Buffer.first) AUDIO.Buffer.first = n;
 
         buffer->prev = NULL;
         buffer->next = NULL;
@@ -1004,7 +1009,7 @@ bool ExportWaveAsCode(Wave wave, const char *fileName)
 // Play a sound
 void PlaySound(Sound sound)
 {
-    PlayAudioBuffer(sound.stream.buffer);
+    PlayAudioStream(sound.stream);
 }
 
 // Play a sound in the multichannel buffer pool
@@ -1059,6 +1064,7 @@ void PlaySoundMulti(Sound sound)
     AUDIO.MultiChannel.pool[index]->pitch = sound.stream.buffer->pitch;
     AUDIO.MultiChannel.pool[index]->audioCallback = sound.stream.buffer->audioCallback;
     AUDIO.MultiChannel.pool[index]->audioCallbackData = sound.stream.buffer->audioCallbackData;
+    AUDIO.MultiChannel.pool[index]->processor = sound.stream.buffer->processor;
     
     AUDIO.MultiChannel.pool[index]->looping = sound.stream.buffer->looping;
     AUDIO.MultiChannel.pool[index]->usage = sound.stream.buffer->usage;
@@ -1621,7 +1627,7 @@ static void MusicStreamCallbackWav(void* buffer, unsigned int nframes, void* dat
     drwav* ctx = (drwav*)data;
     // NOTE: Returns the number of samples to process (not required)
     if (ctx->bitsPerSample == 16) drwav_read_pcm_frames_s16(ctx, nframes, (short*)buffer);
-    else if (ctx->bitsPerSample == 32) drwav_read_pcm_frames_f32(ctx, nframes, (short*)buffer);
+    else if (ctx->bitsPerSample == 32) drwav_read_pcm_frames_f32(ctx, nframes, (float*)buffer);
 }
 #endif
 
@@ -2119,6 +2125,57 @@ void SetAudioStreamCallback(AudioStream stream, void callback(void*, unsigned in
     }
 }
 
+
+// Add processor to audio stream. Contrary to buffers, the order of processors is important.
+// The new processor must be added at the end. As there aren't supposed to be a lot of processors attached to
+// a given stream, we iterate through the list to find the end. That way we don't need a pointer to the last element.
+void AddAudioStreamProcessor(AudioStream stream, void (*process)(float*, unsigned int))
+{
+    ma_mutex_lock(&AUDIO.System.lock); // necessary evil.
+
+    rAudioProcessor* processor = (rAudioProcessor*)RL_CALLOC(1, sizeof(rAudioProcessor));
+    processor->process = process;
+
+    rAudioProcessor* last = stream.buffer->processor;
+    while (last && last->next)
+    {
+        last = last->next;
+    }
+    if (last)
+    {
+        processor->prev = last;
+        last->next = processor;
+    }
+    else
+    {
+        stream.buffer->processor = processor;
+    }
+
+    ma_mutex_unlock(&AUDIO.System.lock);
+}
+
+void RemoveAudioStreamProcessor(AudioStream stream, void (*process)(float*, unsigned int))
+{
+    ma_mutex_lock(&AUDIO.System.lock);
+
+    rAudioProcessor* processor = stream.buffer->processor;
+    while (processor)
+    {
+        rAudioProcessor* next = processor->next;
+        rAudioProcessor* prev = processor->prev;
+        if (processor->process == process)
+        {
+            if (stream.buffer->processor == processor) stream.buffer->processor = next;
+            if (prev) prev->next = next;
+            if (next) next->prev = prev;
+            RL_FREE(processor);
+        }
+        processor = next;
+    }
+    ma_mutex_unlock(&AUDIO.System.lock);
+}
+
+
 //----------------------------------------------------------------------------------
 // Module specific Functions Definition
 //----------------------------------------------------------------------------------
@@ -2315,6 +2372,14 @@ static void OnSendAudioDataToDevice(ma_device *pDevice, void *pFramesOut, const
                         float *framesOut = (float *)pFramesOut + (framesRead*AUDIO.System.device.playback.channels);
                         float *framesIn = tempBuffer;
 
+                        // apply processors chain
+                        rAudioProcessor *processor =  audioBuffer->processor;
+                        while (processor)
+                        {
+                            processor->process(framesIn, framesJustRead);
+                            processor = processor->next;
+                        }
+
                         MixAudioFrames(framesOut, framesIn, framesJustRead, audioBuffer->volume);
 
                         framesToRead -= framesJustRead;

src/raudio.h

@@ -88,11 +88,11 @@ typedef struct Wave {
 } Wave;
 
 typedef struct rAudioBuffer rAudioBuffer;
+typedef struct rAudioProcessor rAudioProcessor;
 
 // AudioStream, custom audio stream
 typedef struct AudioStream {
     rAudioBuffer *buffer;       // Pointer to internal data used by the audio system
-
     unsigned int sampleRate;    // Frequency (samples per second)
     unsigned int sampleSize;    // Bit depth (bits per sample): 8, 16, 32 (24 not supported)
     unsigned int channels;      // Number of channels (1-mono, 2-stereo, ...)
@@ -191,7 +191,8 @@ void SetAudioStreamVolume(AudioStream stream, float volume);    // Set volume fo
 void SetAudioStreamPitch(AudioStream stream, float pitch);      // Set pitch for audio stream (1.0 is base level)
 void SetAudioStreamBufferSizeDefault(int size);                 // Default size for new audio streams
 void SetAudioStreamCallback(AudioStream stream, void callback(void*, unsigned int, void*), void* callbackData);  // Audio thread callback to request new data
-
+void AddAudioStreamProcessor(AudioStream stream, void (*process)(float*, unsigned int));
+void RemoveAudioStreamProcessor(AudioStream stream, void (*process)(float*, unsigned int));
 #ifdef __cplusplus
 }
 #endif

src/raylib.h

@@ -426,11 +426,12 @@ typedef struct Wave {
 } Wave;
 
 typedef struct rAudioBuffer rAudioBuffer;
+typedef struct rAudioProcessor rAudioProcessor;
 
 // AudioStream, custom audio stream
 typedef struct AudioStream {
     rAudioBuffer *buffer;       // Pointer to internal data used by the audio system
-
+    rAudioProcessor* processor;
     unsigned int sampleRate;    // Frequency (samples per second)
     unsigned int sampleSize;    // Bit depth (bits per sample): 8, 16, 32 (24 not supported)
     unsigned int channels;      // Number of channels (1-mono, 2-stereo, ...)
@@ -1531,6 +1532,8 @@ RLAPI void SetAudioStreamVolume(AudioStream stream, float volume);    // Set vol
 RLAPI void SetAudioStreamPitch(AudioStream stream, float pitch);      // Set pitch for audio stream (1.0 is base level)
 RLAPI void SetAudioStreamBufferSizeDefault(int size);                 // Default size for new audio streams
 RLAPI void SetAudioStreamCallback(AudioStream stream, void callback(void*, unsigned int, void*), void* callbackData);      // Audio thread callback to request new data
+RLAPI void AddAudioStreamProcessor(AudioStream stream, void (*process)(float*, unsigned int));
+RLAPI void RemoveAudioStreamProcessor(AudioStream stream, void (*process)(float*, unsigned int));
 
 #if defined(__cplusplus)
 }