Implemented stereo sound.

projects/examples/dev.time.usm

@@ -43,11 +43,9 @@ BRK
 	~Time.second ~current.second NEQ #01 JNZ BRK
 	~Time.second =current.second
 
-	~Time.second #03 AND ^$no-sound JNZ
+	#1444 =Audio.ch1adsr
-	#ffff =Audio.ch1adsr
 	~Time.second #1d ADD =Audio.ch1pitch
-	#ff =Audio.ch1vol
+	~Time.second #03 AND #4b MUL #0f ADD =Audio.ch1vol
-	$no-sound
 
 	( clear )
 	#0080 SCALEX #0080 SCALEY ~needles.sx ~needles.sy #00 ,draw-line JSR2

src/emulator.c

@@ -51,26 +51,29 @@ Uint8 font[][8] = {
 
 #define SAMPLE_FREQUENCY 48000
 
-static Uint32 note_periods[12] = { /* middle C (C4) is note 60 */
+static Uint32 note_periods[12] = {
-	(Uint32) 0xfa7e * SAMPLE_FREQUENCY, /* C-1 */
+	/* middle C (C4) is note 60 */
-	(Uint32) 0xec6f * SAMPLE_FREQUENCY,
+	(Uint32)0xfa7e * SAMPLE_FREQUENCY, /* C-1 */
-	(Uint32) 0xdf2a * SAMPLE_FREQUENCY, /* D-1 */
+	(Uint32)0xec6f * SAMPLE_FREQUENCY,
-	(Uint32) 0xd2a4 * SAMPLE_FREQUENCY,
+	(Uint32)0xdf2a * SAMPLE_FREQUENCY, /* D-1 */
-	(Uint32) 0xc6d1 * SAMPLE_FREQUENCY, /* E-1 */
+	(Uint32)0xd2a4 * SAMPLE_FREQUENCY,
-	(Uint32) 0xbba8 * SAMPLE_FREQUENCY, /* F-1 */
+	(Uint32)0xc6d1 * SAMPLE_FREQUENCY, /* E-1 */
-	(Uint32) 0xb120 * SAMPLE_FREQUENCY,
+	(Uint32)0xbba8 * SAMPLE_FREQUENCY, /* F-1 */
-	(Uint32) 0xa72f * SAMPLE_FREQUENCY, /* G-1 */
+	(Uint32)0xb120 * SAMPLE_FREQUENCY,
-	(Uint32) 0x9dcd * SAMPLE_FREQUENCY,
+	(Uint32)0xa72f * SAMPLE_FREQUENCY, /* G-1 */
-	(Uint32) 0x94f2 * SAMPLE_FREQUENCY, /* A-1 */
+	(Uint32)0x9dcd * SAMPLE_FREQUENCY,
-	(Uint32) 0x8c95 * SAMPLE_FREQUENCY,
+	(Uint32)0x94f2 * SAMPLE_FREQUENCY, /* A-1 */
-	(Uint32) 0x84b2 * SAMPLE_FREQUENCY  /* B-1 */
+	(Uint32)0x8c95 * SAMPLE_FREQUENCY,
+	(Uint32)0x84b2 * SAMPLE_FREQUENCY  /* B-1 */
 };
 
-static struct audio_channel {
+typedef struct audio_channel {
 	Uint32 period, count;
 	Sint32 age, a, d, s, r;
-	Sint16 volume, value;
+	Sint16 value[2];
-} channels[4];
+	Sint8 volume[2], phase;
+} Channel;
+Channel channels[4];
 
 static SDL_Window *gWindow;
 static SDL_Renderer *gRenderer;
@@ -236,39 +239,58 @@ togglezoom(Uxn *u)
 	redraw(pixels, u);
 }
 
+Sint16
+audio_envelope(Channel *c) {
+	if (c->age < c->a)
+		return 0x0888 * c->age / c->a;
+	else if (c->age < c->d)
+		return 0x0444 * (2 * c->d - c->a - c->age) / (c->d - c->a);
+	else if (c->age < c->s)
+		return 0x0444;
+	else if (c->age < c->r)
+		return 0x0444 * (c->r - c->age) / (c->r - c->s);
+	else
+		return 0x0000;
+}
+
 void
 audio_callback(void* userdata, Uint8* stream, int len) {
 	Sint16 *samples = (Sint16 *) stream;
 	int i, j;
-	len >>= 1; /* use len for number of samples, not bytes */
+	len >>= 2; /* use len for number of samples, not bytes */
-	for (j = 0; j < len; ++j) samples[j] = 0;
+	for (j = len * 2 - 1; j >= 0; --j) samples[j] = 0;
 	for (i = 0; i < 4; ++i) {
-		struct audio_channel *c = &channels[i];
+		Channel *c = &channels[i];
-		if (!c->volume) continue;
 		if (c->period < (1 << 20)) continue;
 		for (j = 0; j < len; ++j) {
 			c->age += 1;
 			c->count += 1 << 20;
 			while (c->count > c->period) {
-				int mul = c->value < 0 ? c->volume : -c->volume;
+				Sint16 mul;
 				c->count -= c->period;
-				if (c->age < c->a)
+				c->phase = !c->phase;
-					c->value = mul * c->age / c->a;
+				mul = (c->phase * 2 - 1) * audio_envelope(c);
-				else if (c->age < c->d)
+				c->value[0] = mul * c->volume[0];
-					c->value = mul * (2 * c->d - c->a - c->age) / 2 / (c->d - c->a);
+				c->value[1] = mul * c->volume[1];
-				else if (c->age < c->s)
-					c->value = mul / 2;
-				else if (c->age < c->r)
-					c->value = mul * (c->r - c->age) / 2 / (c->r - c->s);
-				else
-					c->volume = c->value = 0;
 			}
-			samples[j] += c->value;
+			samples[j * 2] += c->value[0];
+			samples[j * 2 + 1] += c->value[1];
 		}
 	}
 	(void) userdata;
 }
 
+void
+silence(void) {
+	int i;
+	for (i = 0; i < 4; ++i) {
+		Channel *c = &channels[i];
+		c->volume[0] = 0;
+		c->volume[1] = 0;
+		c->period = 0;
+	}
+}
+
 void
 quit(void)
 {
@@ -301,11 +323,12 @@ init(void)
 	if(!(pixels = (Uint32 *)malloc(WIDTH * HEIGHT * sizeof(Uint32))))
 		return error("Pixels", "Failed to allocate memory");
 	clear(pixels);
+	silence();
 	SDL_StartTextInput();
 	SDL_ShowCursor(SDL_DISABLE);
 	as.freq = SAMPLE_FREQUENCY;
 	as.format = AUDIO_S16;
-	as.channels = 1;
+	as.channels = 2;
 	as.callback = audio_callback;
 	as.samples = 2048;
 	audio_id = SDL_OpenAudioDevice(NULL, 0, &as, NULL, 0);
@@ -474,17 +497,18 @@ audio_poke(Uxn *u, Uint16 ptr, Uint8 b0, Uint8 b1)
 {
 	Uint8 *m = u->ram.dat;
 	if (b0 & 1) {
-		Uint16 channel_addr = ptr + (b0 & 0x6);
+		Uint16 addr = ptr + (b0 & 0x6);
-		struct audio_channel *c = &channels[(b0 & 0x6) >> 1];
+		Channel *c = &channels[(b0 & 0x6) >> 1];
 		SDL_LockAudioDevice(audio_id);
-		c->period = note_periods[m[channel_addr + 8] % 12] >> (m[channel_addr + 8] / 12);
+		c->period = note_periods[m[addr + 8] % 12] >> (m[addr + 8] / 12);
 		c->count %= c->period;
-		c->volume = m[channel_addr + 9] << 5;
+		c->volume[0] = (m[addr + 9] >> 4) & 0xf;
+		c->volume[1] = m[addr + 9] & 0xf;
 		c->age = 0;
-		c->a = ((m[channel_addr] >> 4) & 0xf) * (SAMPLE_FREQUENCY >> 4);
+		c->a = (SAMPLE_FREQUENCY >> 4) * ((m[addr] >> 4) & 0xf);
-		c->d = c->a + (m[channel_addr] & 0xf) * (SAMPLE_FREQUENCY >> 4);
+		c->d = c->a + (SAMPLE_FREQUENCY >> 4) * (m[addr] & 0xf);
-		c->s = c->d + ((m[channel_addr + 1] >> 4) & 0xf) * (SAMPLE_FREQUENCY >> 4);
+		c->s = c->d + (SAMPLE_FREQUENCY >> 4) * ((m[addr + 1] >> 4) & 0xf);
-		c->r = c->s + (m[channel_addr + 1] & 0xf) * (SAMPLE_FREQUENCY >> 4);
+		c->r = c->s + (SAMPLE_FREQUENCY >> 4) * (m[addr + 1] & 0xf);
 		SDL_UnlockAudioDevice(audio_id);
 	}
 	return b1;