Added simple SDL mixer example

project/jni/application/simplemixer/simplemixer.c

@@ -0,0 +1,288 @@
+/*
+ * SimpleMixer 1.1
+ *
+ * Simple sound mixing example for SDL.
+ *
+ * (C) David Olofson, 2003
+ */
+
+#include <stdlib.h>
+#include <signal.h>
+#include "SDL.h"
+#include "SDL_audio.h"
+
+#define	SM_SOUNDS	4
+#define	SM_VOICES	4
+
+
+typedef struct
+{
+	Uint8	*data;
+	Uint32	length;
+} SM_sound;
+
+
+typedef struct
+{
+	Sint16	*data;
+	int	length;
+	int	position;
+	int	l_vol;
+	int	r_vol;
+} SM_voice;
+
+
+SM_sound sounds[SM_SOUNDS];
+SM_voice voices[SM_VOICES];
+SDL_AudioSpec audiospec;
+int die = 0;
+
+
+void sm_play(unsigned voice, unsigned sound, float lvol, float rvol)
+{
+	if(voice >= SM_VOICES || sound >= SM_SOUNDS)
+		return;
+
+	/* Stop voice */
+	voices[voice].data = NULL;
+
+	/* Reprogram */
+	voices[voice].length = sounds[sound].length / 2;
+	voices[voice].position = 0;
+	voices[voice].l_vol = (int)(lvol * 256.0);
+	voices[voice].r_vol = (int)(rvol * 256.0);
+
+	/* Start! */
+	voices[voice].data = (Sint16*)(sounds[sound].data);
+}
+
+
+static void sm_mixer(void *ud, Uint8 *stream, int len)
+{
+	int vi, s;
+	Sint16 *buf = (Sint16 *)stream;
+
+	/* Clear the buffer */
+	memset(buf, 0, len);
+
+	/* 2 channels, 2 bytes/sample = 4 bytes/frame */
+        len /= 4;
+
+	/* For each voice... */
+	for(vi = 0; vi < SM_VOICES; ++vi)
+	{
+		SM_voice *v = &voices[vi];
+		if(!v->data)
+			continue;
+
+		/* For each sample... */
+		for(s = 0; s < len; ++s)
+		{
+			if(v->position >= v->length)
+			{
+				v->data = NULL;
+				break;
+			}
+			buf[s * 2] += v->data[v->position] * v->l_vol >> 8;
+			buf[s * 2 + 1] += v->data[v->position] * v->r_vol >> 8;
+			++v->position;
+		}
+	}
+}
+
+
+int sm_open(void)
+{
+	SDL_AudioSpec as;
+
+	memset(sounds, 0, sizeof(sounds));
+	memset(voices, 0, sizeof(voices));
+
+	if(SDL_InitSubSystem(SDL_INIT_AUDIO|SDL_INIT_VIDEO) < 0)
+		return -2;
+
+	as.freq = 44100;
+	as.format = AUDIO_S16SYS;
+	as.channels = 2;
+	as.samples = 1024;
+	as.callback = sm_mixer;
+	if(SDL_OpenAudio(&as, &audiospec) < 0)
+		return -3;
+
+	if(audiospec.format != AUDIO_S16SYS)
+		return -4;
+
+	SDL_PauseAudio(0);
+	return 0;
+}
+
+
+void sm_close(void)
+{
+	int i;
+	SDL_PauseAudio(1);
+	for(i = 0; i < SM_VOICES; ++i)
+		voices[i].data = NULL;
+	SDL_CloseAudio();
+	for(i = 0; i < SM_SOUNDS; ++i)
+		SDL_FreeWAV(sounds[i].data);
+	memset(sounds, 0, sizeof(sounds));
+	memset(voices, 0, sizeof(voices));
+}
+
+
+void flip_endian(Uint8 *data, int length)
+{
+	int i;
+	for(i = 0; i < length; i += 2)
+	{
+		int x = data[i];
+		data[i] = data[i + 1];
+		data[i + 1] = x;
+	}
+}
+
+
+int sm_load(int sound, const char *file)
+{
+	int failed = 0;
+	SDL_AudioSpec spec;
+	if(sounds[sound].data)
+		SDL_FreeWAV(sounds[sound].data);
+	sounds[sound].data = NULL;
+	if(SDL_LoadWAV(file, &spec, &sounds[sound].data,
+			&sounds[sound].length) == NULL)
+		return -1;
+	if(spec.freq != 44100)
+		fprintf(stderr, "WARNING: File '%s' is not 44.1 kHz."
+				" Might sound weird...\n", file);
+	if(spec.channels != 1)
+	{
+		fprintf(stderr, "Only mono sounds are supported!\n");
+		failed = 1;
+	}
+	switch(spec.format)
+	{
+	  case AUDIO_S16LSB:
+	  case AUDIO_S16MSB:
+		if(spec.format != AUDIO_S16SYS)
+			flip_endian(sounds[sound].data, sounds[sound].length);
+		break;
+	  default:
+		fprintf(stderr, "Unsupported sample format!\n");
+		failed = 1;
+		break;
+	}
+	if(failed)
+	{
+		SDL_FreeWAV(sounds[sound].data);
+		sounds[sound].data = NULL;
+		return -2;
+	}
+	return 0;
+}
+
+
+void breakhandler(int a)
+{
+	die = 1;
+}
+
+
+int main(int argc, char *argv[])
+{
+	const char *bd = "#...#...#...#..##...#...#...#.##";
+	const char *cl = "....#..*....#....*..#....*..#.**";
+	const char *cb = "#...*..#..*...#.#...*..#..*..*#*";
+	const char *hh = "..#...#...#...#...#...#...#...#.";
+	int res;
+	Uint32 step = 0;
+	Sint32 timer;
+	SDL_Event event;
+	int color = 0;
+	if(SDL_Init(0) < 0)
+		return -1;
+
+/*
+	atexit(SDL_Quit);
+	signal(SIGTERM, breakhandler);
+	signal(SIGINT, breakhandler);
+*/
+
+	if(sm_open() < 0)
+	{
+		fprintf(stderr, "Couldn't start mixer!\n");
+		SDL_Quit();
+		return -1;
+	}
+	
+	SDL_SetVideoMode(320, 200, 16, SDL_SWSURFACE);
+
+	res = 0;
+	res |= sm_load(0, "808-bassdrum.wav");
+	res |= sm_load(1, "808-clap.wav");
+	res |= sm_load(2, "808-cowbell.wav");
+	res |= sm_load(3, "808-hihat.wav");
+	if(res)
+	{
+		sm_close();
+		SDL_Quit();
+		fprintf(stderr, "Couldn't load sounds!\n");
+		return -1;
+	}
+
+	/*
+	 * Of course, playing this stuff would be
+	 * much better done in the audio callback,
+	 * since the timing out here jitters a lot.
+	 *
+	 * However, this is just a fun hack to get
+	 * the thing to make some sound, without
+	 * slapping in a game or something. :-)
+	 */
+	SDL_Delay(200);
+	timer = (Sint32)SDL_GetTicks();
+	while(!die)
+	{
+		if('#' == bd[step])
+			sm_play(0, 0, 1.0, 1.0);
+
+		if('#' == cl[step])
+			sm_play(1, 1, 0.6, 0.5);
+		else if('*' == cl[step])
+			sm_play(1, 1, 0.2, 0.3);
+
+		if('#' == cb[step])
+			sm_play(2, 2, 0.3, 0.2);
+		else if('*' == cb[step])
+			sm_play(2, 2, 0.1, 0.2);
+
+		if('#' == hh[step])
+			sm_play(3, 3, 0.3, 0.4);
+
+		step = (step + 1) % 32;
+
+		timer += 120;
+		
+		while(SDL_PollEvent(&event) > 0)
+		{
+			if(event.type & (SDL_KEYUP | SDL_KEYDOWN))
+			{
+				Uint8 *keys = SDL_GetKeyState(NULL);
+				if(keys[SDLK_ESCAPE])
+					die = 1;
+			}
+		}
+
+		SDL_FillRect(SDL_GetVideoSurface(), NULL, color);
+		color += 10;
+		SDL_Flip(SDL_GetVideoSurface()); // Program is required to call SDL_Flip(), or it will invoke Application Not Responding dialog
+		
+		while(((Sint32)SDL_GetTicks() - timer) < 0)
+			SDL_Delay(10);
+	}
+
+	sm_close();
+	SDL_Quit();
+	return 0;
+}