--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/audio.c	Thu Mar 31 00:07:37 2016 -0700
@@ -0,0 +1,69 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include "audio.h"
+#include "system.h"
+
+#define BUFFER_INC_RES 1000000000UL
+
+audio *alloc_audio(uint32_t master_clock, uint32_t clock_div, int sample_rate, int buffer_size)
+{
+	size_t alloc_size = sizeof(audio) + buffer_size * sizeof(int16_t) * 2;
+	audio *context = malloc(alloc_size);
+	memset(context, 0, alloc_size);
+	context->writebuffer = context->buffer;
+	context->playbuffer = context->buffer + buffer_size;
+	
+	context->buffer_size = buffer_size;
+	context->clock_inc = clock_div;
+	context->buffer_inc = ((BUFFER_INC_RES * (uint64_t)sample_rate) / (uint64_t)master_clock) * clock_div;
+	for (int i = 0; i < NUM_CHANNELS; i++)
+	{
+		context->value[i] = context->volume[i] << 5;
+	}
+}
+
+void audio_run(audio *context, uint32_t target)
+{
+	while (context->cycles < target)
+	{
+		for (int i = 0; i < 4; i++)
+		{
+			if (context->timer_cur[i]) {
+				context->timer_cur[i]--;
+				if (!context->timer_cur[i]) {
+					context->value[i] = context->value[i] ? 0 : (context->volume[i] << 5);
+				}
+			} else {
+				context->timer_cur[i] = context->timer_load[i];
+			}
+		}
+		context->buffer_fraction += context->buffer_inc;
+		if (context->buffer_fraction >= BUFFER_INC_RES) {
+			context->buffer_fraction -= BUFFER_INC_RES;
+			context->writebuffer[context->buffer_pos++] = 
+				context->value[0] + context->value[1] + context->value[2] + context->value[3];
+			if (context->buffer_pos == context->buffer_size) {
+				int16_t *tmp = context->playbuffer;
+				context->playbuffer = context->writebuffer;
+				context->writebuffer = tmp;
+				system_present_audio(context->playbuffer);
+				context->buffer_pos = 0;
+			}
+		}
+		context->cycles += context->clock_inc;
+	}
+}
+
+void audio_write_freq(audio *context, int channel, uint16_t value)
+{
+	context->timer_cur[channel] = context->timer_load[channel] = value;
+}
+
+void audio_write_vol(audio *context, int pair, uint16_t value)
+{
+	int channel = pair * 2;
+	context->value[channel] = context->volume[channel] = value >> 8;
+	channel++;
+	context->value[channel] = context->volume[channel] = value;
+}