usynth

commit a63175a99c62a0d07ccf4fa51c36e11b3bef0add
parent cee75e2bb82c9a8f9430164a7d5efe92ee581133
Author: zavok <an2qzavok@gmail.com>
Date:   Mon,  4 Nov 2019 20:12:25 +0300

implemented polyphony

Diffstat:
M
fm.c
 | 
63
+++++++++++++++++++++++++++++++++++++++++++++++++++++----------

1 file changed, 53 insertions(+), 10 deletions(-)
diff --git a/fm.c b/fm.c
@@ -16,18 +16,46 @@ double tune[]={
 30.87, //B  47
 };
 
-size_t c, dt;
+size_t c;
 int16_t vol;
+struct schan{
+	int id;
+	uint8_t note;
+	uint8_t velocity;
+};
+struct schan fm_sounds[32];
+
+int16_t fm_synth(int);
+int16_t fm_mix(void);
 
-int16_t fmsynth(void);
+int16_t
+fm_synth(int i)
+{
+	struct schan *sc;
+	sc = &fm_sounds[i];
+	if (sc->id < 0) return 0;
+	if (sc->velocity == 0) return 0;
+	size_t dt;
+	int16_t out;
+	out = 0x7fff * sc->velocity / 0xff;
+	dt = 44100.0 / (tune[sc->note%12] * (1 << (sc->note/12)));
+	if (c%dt > dt/2) out = -out;
+	return out;
+}
 
 int16_t
-fm_synth(void)
+fm_mix(void)
 {
+	int64_t out;
+	int i;
 	c++;
-	if (dt == 0) return 0;
-	if (c%dt > dt / 2) return vol;
-	return -vol;
+	out = 0;
+	for (i=0; i<32; i++){
+		out += fm_synth(i);
+	}
+	if (out > 0x7fff) out = 0x7fff;
+	if (out < -0x7fff) out = -0x7fff;
+	return out;
 }
 
 void
@@ -35,19 +63,34 @@ fm_fillbuf(int16_t *buf, size_t nsamples)
 {
 	size_t i;
 	for (i=0; i < nsamples; i+=2){
-		buf[i] = buf[i+1] = fm_synth();
+		buf[i] = buf[i+1] = fm_mix();
 	}
 }
 
 void
 fm_note_on(uint8_t *mm)
 {
-	dt = 44100.0 / (tune[mm[2]%12] * (1 << mm[2]/12)); 
-	vol = 0x7fff * mm[3] / 0xff;
+	int i, nmin, nmax;
+	nmin = 32;
+	nmax = 32;
+	for (i=0;i<32;i++){
+		if (fm_sounds[i].id<fm_sounds[nmin].id) nmin = i;
+		if (fm_sounds[i].id>fm_sounds[nmax].id) nmax = i;
+		//if (fm_sounds[i].id<=0) break;
+	}
+	fm_sounds[nmin].id = nmax+1;
+	fm_sounds[nmin].note = mm[2];
+	fm_sounds[nmin].velocity = mm[3];
 }
 
 void
 fm_note_off(uint8_t *mm)
 {
-	vol = 0;
+	int i;
+	for (i=0; i<32; i++){
+		if (fm_sounds[i].note == mm[2]){
+			fm_sounds[i].velocity = mm[3];
+			fm_sounds[i].id = -1;
+		}
+	}
 }