dm: sandbox: Update sound to use two buffers

At present we use a single buffer for sound which means we cannot be playing one sound while queueing up the next. This wouldn't matter except that a long sound (more than a second) has to be created as a single buffer, thus using a lot of memory. To better mimic what real sound drivers do, add support for double buffering in sandbox. Signed-off-by: Simon Glass <sjg@chromium.org>

dm: sandbox: Update sound to use two buffers
At present we use a single buffer for sound which means we cannot be playing one sound while queueing up the next. This wouldn't matter except that a long sound (more than a second) has to be created as a single buffer, thus using a lot of memory. To better mimic what real sound drivers do, add support for double buffering in sandbox. Signed-off-by: Simon Glass <sjg@chromium.org>
Simon Glass
1 parent e96fa6c911
Showing 1 changed file with 63 additions and 25 deletions Side-by-side Diff
arch/sandbox/cpu/sdl.c
@@ -13,6 +13,21 @@
 	SAMPLE_RATE	= 22050,
 };
  
+/**
+ * struct buf_info - a data buffer holding audio data
+ *
+ * @pos:	Current position playing in audio buffer
+ * @size:	Size of data in audio buffer (0=empty)
+ * @alloced:	Allocated size of audio buffer (max size it can hold)
+ * @data:	Audio data
+ */
+struct buf_info {
+	uint pos;
+	uint size;
+	uint alloced;
+	uint8_t *data;
+};
+
 static struct sdl_info {
 	SDL_Surface *screen;
 	int width;
  
  
@@ -20,12 +35,11 @@
 	int depth;
 	int pitch;
 	uint frequency;
-	uint audio_pos;
-	uint audio_size;
 	uint sample_rate;
-	uint8_t *audio_data;
 	bool audio_active;
 	bool inited;
+	int cur_buf;
+	struct buf_info buf[2];
 } sdl;
  
 static void sandbox_sdl_poll_events(void)
  
  
  
  
  
@@ -243,24 +257,37 @@
  
 void sandbox_sdl_fill_audio(void *udata, Uint8 *stream, int len)
 {
+	struct buf_info *buf;
 	int avail;
+	int i;
  
-	avail = sdl.audio_size - sdl.audio_pos;
-	if (avail < len)
-		len = avail;
+	for (i = 0; i < 2; i++) {
+		buf = &sdl.buf[sdl.cur_buf];
+		avail = buf->size - buf->pos;
+		if (avail <= 0) {
+			sdl.cur_buf = 1 - sdl.cur_buf;
+			continue;
+		}
+		if (avail > len)
+			avail = len;
  
-	SDL_MixAudio(stream, sdl.audio_data + sdl.audio_pos, len,
-		     SDL_MIX_MAXVOLUME);
-	sdl.audio_pos += len;
+		SDL_MixAudio(stream, buf->data + buf->pos, avail,
+			     SDL_MIX_MAXVOLUME);
+		buf->pos += avail;
+		len -= avail;
  
-	/* Loop if we are at the end */
-	if (sdl.audio_pos == sdl.audio_size)
-		sdl.audio_pos = 0;
+		/* Move to next buffer if we are at the end */
+		if (buf->pos == buf->size)
+			buf->size = 0;
+		else
+			break;
+	}
 }
  
 int sandbox_sdl_sound_init(void)
 {
 	SDL_AudioSpec wanted;
+	int i;
  
 	if (sandbox_sdl_ensure_init())
 		return -1;
  
@@ -276,13 +303,20 @@
 	wanted.callback = sandbox_sdl_fill_audio;
 	wanted.userdata = NULL;
  
-	sdl.audio_size = sizeof(uint16_t) * wanted.freq;
-	sdl.audio_data = malloc(sdl.audio_size);
-	if (!sdl.audio_data) {
-		printf("%s: Out of memory\n", __func__);
-		return -1;
+	for (i = 0; i < 2; i++) {
+		struct buf_info *buf = &sdl.buf[i];
+
+		buf->alloced = sizeof(uint16_t) * wanted.freq * wanted.channels;
+		buf->data = malloc(buf->alloced);
+		if (!buf->data) {
+			printf("%s: Out of memory\n", __func__);
+			if (i == 1)
+				free(sdl.buf[0].data);
+			return -1;
+		}
+		buf->pos = 0;
+		buf->size = 0;
 	}
-	sdl.audio_pos = 0;
  
 	if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) {
 		printf("Unable to initialize SDL audio: %s\n", SDL_GetError());
  
  
  
@@ -296,23 +330,27 @@
 	}
 	sdl.audio_active = true;
 	sdl.sample_rate = wanted.freq;
+	sdl.cur_buf = 0;
  
 	return 0;
  
 err:
-	free(sdl.audio_data);
+	for (i = 0; i < 2; i++)
+		free(sdl.buf[i].data);
 	return -1;
 }
  
 int sandbox_sdl_sound_start(uint frequency)
 {
+	struct buf_info *buf = &sdl.buf[0];
+
 	if (!sdl.audio_active)
 		return -1;
 	sdl.frequency = frequency;
-	sound_create_square_wave(sdl.sample_rate,
-				 (unsigned short *)sdl.audio_data,
-				 sdl.audio_size, frequency);
-	sdl.audio_pos = 0;
+	sound_create_square_wave(sdl.sample_rate, (unsigned short *)buf->data,
+				 buf->alloced, frequency);
+	buf->pos = 0;
+	buf->size = buf->alloced;
 	SDL_PauseAudio(0);
  
 	return 0;
...	...	@@ -13,6 +13,21 @@
13	13	SAMPLE_RATE = 22050,
14	14	};
15	15
	16	+/**
	17	+ * struct buf_info - a data buffer holding audio data
	18	+ *
	19	+ * @pos: Current position playing in audio buffer
	20	+ * @size: Size of data in audio buffer (0=empty)
	21	+ * @alloced: Allocated size of audio buffer (max size it can hold)
	22	+ * @data: Audio data
	23	+ */
	24	+struct buf_info {
	25	+ uint pos;
	26	+ uint size;
	27	+ uint alloced;
	28	+ uint8_t *data;
	29	+};
	30	+
16	31	static struct sdl_info {
17	32	SDL_Surface *screen;
18	33	int width;
19	34
20	35
...	...	@@ -20,12 +35,11 @@
20	35	int depth;
21	36	int pitch;
22	37	uint frequency;
23		- uint audio_pos;
24		- uint audio_size;
25	38	uint sample_rate;
26		- uint8_t *audio_data;
27	39	bool audio_active;
28	40	bool inited;
	41	+ int cur_buf;
	42	+ struct buf_info buf[2];
29	43	} sdl;
30	44
31	45	static void sandbox_sdl_poll_events(void)
32	46
33	47
34	48
35	49
36	50
...	...	@@ -243,24 +257,37 @@
243	257
244	258	void sandbox_sdl_fill_audio(void udata, Uint8 stream, int len)
245	259	{
	260	+ struct buf_info *buf;
246	261	int avail;
	262	+ int i;
247	263
248		- avail = sdl.audio_size - sdl.audio_pos;
249		- if (avail < len)
250		- len = avail;
	264	+ for (i = 0; i < 2; i++) {
	265	+ buf = &sdl.buf[sdl.cur_buf];
	266	+ avail = buf->size - buf->pos;
	267	+ if (avail <= 0) {
	268	+ sdl.cur_buf = 1 - sdl.cur_buf;
	269	+ continue;
	270	+ }
	271	+ if (avail > len)
	272	+ avail = len;
251	273
252		- SDL_MixAudio(stream, sdl.audio_data + sdl.audio_pos, len,
253		- SDL_MIX_MAXVOLUME);
254		- sdl.audio_pos += len;
	274	+ SDL_MixAudio(stream, buf->data + buf->pos, avail,
	275	+ SDL_MIX_MAXVOLUME);
	276	+ buf->pos += avail;
	277	+ len -= avail;
255	278
256		- /* Loop if we are at the end */
257		- if (sdl.audio_pos == sdl.audio_size)
258		- sdl.audio_pos = 0;
	279	+ /* Move to next buffer if we are at the end */
	280	+ if (buf->pos == buf->size)
	281	+ buf->size = 0;
	282	+ else
	283	+ break;
	284	+ }
259	285	}
260	286
261	287	int sandbox_sdl_sound_init(void)
262	288	{
263	289	SDL_AudioSpec wanted;
	290	+ int i;
264	291
265	292	if (sandbox_sdl_ensure_init())
266	293	return -1;
267	294
...	...	@@ -276,13 +303,20 @@
276	303	wanted.callback = sandbox_sdl_fill_audio;
277	304	wanted.userdata = NULL;
278	305
279		- sdl.audio_size = sizeof(uint16_t) * wanted.freq;
280		- sdl.audio_data = malloc(sdl.audio_size);
281		- if (!sdl.audio_data) {
282		- printf("%s: Out of memory\n", __func__);
283		- return -1;
	306	+ for (i = 0; i < 2; i++) {
	307	+ struct buf_info *buf = &sdl.buf[i];
	308	+
	309	+ buf->alloced = sizeof(uint16_t) * wanted.freq * wanted.channels;
	310	+ buf->data = malloc(buf->alloced);
	311	+ if (!buf->data) {
	312	+ printf("%s: Out of memory\n", __func__);
	313	+ if (i == 1)
	314	+ free(sdl.buf[0].data);
	315	+ return -1;
	316	+ }
	317	+ buf->pos = 0;
	318	+ buf->size = 0;
284	319	}
285		- sdl.audio_pos = 0;
286	320
287	321	if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) {
288	322	printf("Unable to initialize SDL audio: %s\n", SDL_GetError());
289	323
290	324
291	325
...	...	@@ -296,23 +330,27 @@
296	330	}
297	331	sdl.audio_active = true;
298	332	sdl.sample_rate = wanted.freq;
	333	+ sdl.cur_buf = 0;
299	334
300	335	return 0;
301	336
302	337	err:
303		- free(sdl.audio_data);
	338	+ for (i = 0; i < 2; i++)
	339	+ free(sdl.buf[i].data);
304	340	return -1;
305	341	}
306	342
307	343	int sandbox_sdl_sound_start(uint frequency)
308	344	{
	345	+ struct buf_info *buf = &sdl.buf[0];
	346	+
309	347	if (!sdl.audio_active)
310	348	return -1;
311	349	sdl.frequency = frequency;
312		- sound_create_square_wave(sdl.sample_rate,
313		- (unsigned short *)sdl.audio_data,
314		- sdl.audio_size, frequency);
315		- sdl.audio_pos = 0;
	350	+ sound_create_square_wave(sdl.sample_rate, (unsigned short *)buf->data,
	351	+ buf->alloced, frequency);
	352	+ buf->pos = 0;
	353	+ buf->size = buf->alloced;
316	354	SDL_PauseAudio(0);
317	355
318	356	return 0;