1 files changed, 119 insertions, 0 deletions
diff --git a/shell/audio/sdl/sound_output.c b/shell/audio/sdl/sound_output.c
new file mode 100644
index 0000000..0758718
--- /dev/null
+++ b/shell/audio/sdl/sound_output.c
@@ -0,0 +1,119 @@
+#include <sys/ioctl.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <SDL/SDL.h>
+
+#include "sound_output.h"
+
+#define UNDERRUN_THRESHOLD 0.5
+
+static int32_t BUFFSIZE;
+static uint8_t *buffer;
+static uint32_t buf_read_pos = 0;
+static uint32_t buf_write_pos = 0;
+static int32_t buffered_bytes = 0;
+
+static int32_t sdl_read_buffer(uint8_t* data, int32_t len)
+{
+	if (buffered_bytes >= len) 
+	{
+		if(buf_read_pos + len <= BUFFSIZE ) 
+		{
+			memcpy(data, buffer + buf_read_pos, len);
+		} 
+		else 
+		{
+			int32_t tail = BUFFSIZE - buf_read_pos;
+			memcpy(data, buffer + buf_read_pos, tail);
+			memcpy(data + tail, buffer, len - tail);
+		}
+		buf_read_pos = (buf_read_pos + len) % BUFFSIZE;
+		buffered_bytes -= len;
+	}
+
+	return len;
+}
+
+
+static void sdl_write_buffer(uint8_t* data, int32_t len)
+{
+	SDL_LockAudio();
+	for(uint32_t i = 0; i < len; i += 4) 
+	{
+		while (buffered_bytes == BUFFSIZE) {
+			SDL_UnlockAudio();
+			usleep(1000);
+			SDL_LockAudio();
+		}
+		*(int32_t*)((char*)(buffer + buf_write_pos)) = *(int32_t*)((char*)(data + i));
+		//memcpy(buffer + buf_write_pos, data + i, 4);
+		buf_write_pos = (buf_write_pos + 4) % BUFFSIZE;
+		buffered_bytes += 4;
+	}
+	SDL_UnlockAudio();
+}
+
+void sdl_callback(void *unused, uint8_t *stream, int32_t len)
+{
+	sdl_read_buffer((uint8_t *)stream, len);
+}
+uint32_t Audio_Init()
+{
+	SDL_AudioSpec aspec, obtained;
+
+	BUFFSIZE = (SOUND_SAMPLES_SIZE * 2 * 2) * 4;
+	buffer = (uint8_t *) malloc(BUFFSIZE);
+
+	/* Add some silence to the buffer */
+	buffered_bytes = 0;
+	buf_read_pos = 0;
+	buf_write_pos = 0;
+
+	aspec.format   = AUDIO_S16SYS;
+	aspec.freq     = SOUND_OUTPUT_FREQUENCY;
+	aspec.channels = 2;
+	aspec.samples  = SOUND_SAMPLES_SIZE;
+	aspec.callback = (sdl_callback);
+	aspec.userdata = NULL;
+
+	/* initialize the SDL Audio system */
+	if (SDL_InitSubSystem (SDL_INIT_AUDIO | SDL_INIT_NOPARACHUTE)) 
+	{
+		printf("SDL: Initializing of SDL Audio failed: %s.\n", SDL_GetError());
+		return 1;
+	}
+
+	/* Open the audio device and start playing sound! */
+	if(SDL_OpenAudio(&aspec, &obtained) < 0) 
+	{
+		printf("SDL: Unable to open audio: %s\n", SDL_GetError());
+		return 1;
+	}
+	
+	SDL_PauseAudio(0);
+	
+	return 0;
+}
+
+void Audio_Write(int16_t* restrict buffer, uint32_t buffer_size)
+{
+	sdl_write_buffer(buffer, buffer_size * 4);
+}
+
+bool Audio_Underrun_Likely() {
+	bool underrun_likely = false;
+	SDL_LockAudio();
+	underrun_likely = buffered_bytes < BUFFSIZE * UNDERRUN_THRESHOLD;
+	SDL_UnlockAudio();
+	return underrun_likely;
+}
+
+void Audio_Close()
+{
+	SDL_PauseAudio(1);
+	SDL_CloseAudio();
+	SDL_QuitSubSystem(SDL_INIT_AUDIO);
+	buffer = NULL;
+}