Added mixer

AudioMixer4_F32.cpp

@@ -0,0 +1,30 @@
+#include "AudioMixer4_F32.h"
+
+void AudioMixer4_F32::update(void) {
+  audio_block_f32_t *in, *out=NULL;
+
+  out = receiveWritable_f32(0);
+  if (!out) return;
+
+  arm_scale_f32(out->data, multiplier[0], out->data, AUDIO_BLOCK_SAMPLES);
+
+  for (int channel=1; channel < 4; channel++) {
+    in = receiveReadOnly_f32(channel);
+    if (!in) {
+      continue;
+    }
+
+    audio_block_f32_t *tmp = allocate_f32();
+
+    arm_scale_f32(in->data, multiplier[channel], tmp->data, AUDIO_BLOCK_SAMPLES);
+    arm_add_f32(out->data, tmp->data, out->data, AUDIO_BLOCK_SAMPLES);
+
+    release(tmp);
+    release(in);
+  }
+
+  if (out) {
+    transmit(out);
+    release(out);
+  }
+}

AudioMixer4_F32.h

@@ -0,0 +1,28 @@
+#ifndef AUDIOMIXER4F32_H
+#define AUDIOMIXER4F32_H
+
+#include <arm_math.h> 
+#include <AudioStream_F32.h>
+
+
+class AudioMixer4_F32 : public AudioStream_F32 {
+public:
+    AudioMixer4_F32() : AudioStream_F32(4, inputQueueArray) {
+      for (int i=0; i<4; i++) multiplier[i] = 0.5;
+    }
+
+    virtual void update(void);
+
+    void gain(unsigned int channel, float gain) {
+      if (channel >= 4) return;
+      if (gain > 127.0f) gain = 127.0f;
+      else if (gain < 0.0f) gain = 0.0f;
+      multiplier[channel] = gain;
+    }
+
+  private:
+    audio_block_f32_t *inputQueueArray[4];
+    float multiplier[4];
+};
+
+#endif