Audio mixer

source/engine/mix.c

@@ -0,0 +1,42 @@
+#include "mix.h"
+#include "stddef.h"
+
+#include "sound.h"
+
+static struct bus bus[256];
+short mastermix[BUF_FRAMES*CHANNELS];
+
+struct bus *first_free_bus() {
+    for (int i = 0; i < 256; i++) {
+        if (!bus[i].on) return &bus[i];
+    }
+
+    return NULL;
+}
+
+void bus_fill_buffers() {
+    for (int i = 0; i < 256; i++) {
+        if (!bus[i].on) continue;
+
+        short *s = (short*)bus[i].sound->data->data;
+
+        for (int k = 0; k < BUF_FRAMES; k++) {
+            for (int j = 0; j < CHANNELS; j++) {
+                bus[i].buf[k*CHANNELS + j] = s[bus[i].sound->frame++];
+                if (bus[i].sound->frame == bus[i].sound->data->frames) {
+                    bus[i].sound->frame = 0;
+                    if (!bus[i].sound->loop) bus[i].on = 0;
+                }
+            }
+        }
+    }
+
+    for (int i = 0; i < BUF_FRAMES*CHANNELS; i++) {
+        mastermix[i] = 0;
+
+        for (int j = 0; j < 256; j++) {
+            if (!bus[j].on) continue;
+            mastermix[i] += bus[j].buf[i];
+        }
+    }
+}

source/engine/mix.h

@@ -0,0 +1,23 @@
+#ifndef MIX_H
+#define MIX_H
+
+#define BUF_FRAMES 4096
+#define CHANNELS 2
+#define MUSIZE 2
+
+struct sound;
+
+
+struct bus {
+    int on;
+    struct sound *sound;
+    short buf[BUF_FRAMES*CHANNELS];
+};
+
+extern short mastermix[BUF_FRAMES*CHANNELS];
+
+struct bus *first_free_bus();
+void bus_fill_buffers();
+
+
+#endif