ref: bc97f719f79c6570db9129b337bb8eb5c5020239
dir: /midi-dobend/
midi: implement pitch wheel
this is an aborted attempt to implement pitch bending (event 0xe0).
this maintains a list of active notes, storing note number, amplitude and bent
frequency; this greatly reduces cpu time spent in run(), also alleviating the
issue of delays between writes to /dev/audio being too great...
it blows chunks:
- greatly complexifies midi note handling
- pitch steps are discrete and too noticeable, actually worsening playback
(blatant example: doom e2m2), but don't yet know where T % f >= f/2 is coming
from or how to fix this
→ i don't yet know what i'm doing nor how to solve this correctly
diff -r 9c4b9c67ff16 sys/src/games/midi.c
--- a/sys/src/games/midi.c Thu Feb 16 20:11:20 2017 +0100
+++ b/sys/src/games/midi.c Wed Feb 22 01:34:39 2017 +0200
@@ -3,19 +3,29 @@
enum { SAMPLE = 44100 };
+typedef struct Note Note;
+typedef struct Tracker Tracker;
+
+struct Note {
+ int nt;
+ Tracker *src;
+ int ch;
+ uchar a;
+ int f;
+ int ½f;
+ Note *n;
+} nl[256], np;
+
struct Tracker {
uchar *data;
char ended;
uvlong t;
- uchar notes[16][128];
+ double bend[16];
int cmd;
} *tr;
-typedef struct Tracker Tracker;
-
int fd, ofd, div, tempo = 500000, ntrack;
uvlong T;
-int freq[128];
void *
emallocz(int size)
@@ -108,32 +118,23 @@
}
void
-run(uvlong n)
+run(uvlong dt)
{
- int samp, j, k, l, no[128];
+ int samp, l;
uchar *s;
- int t, f;
+ int t;
short u;
- Tracker *x;
-
- samp = n - T;
+ Note *n;
+
+ samp = dt - T;
if(samp <= 0)
return;
- memset(no, 0, sizeof no);
- for(x = tr; x < tr + ntrack; x++){
- if(x->ended)
- continue;
- for(j = 0; j < 16; j++)
- for(k = 0; k < 128; k++)
- no[k] += x->notes[j][k];
- }
s = emallocz(samp * 4);
for(l = 0; l < samp; l++){
t = 0;
- for(k = 0; k < 128; k++){
- f = (T % freq[k]) >= freq[k]/2 ? 1 : 0;
- t += f * no[k];
- }
+ for(n = np.n; n != &np; n = n->n)
+ if(T % n->f >= n->½f)
+ t += n->a;
u = t*10;
s[4 * l] = s[4 * l + 2] = u;
s[4 * l + 1] = s[4 * l + 3] = u >> 8;
@@ -144,11 +145,70 @@
}
void
+bend(Tracker *src, int ch, int b)
+{
+ int f;
+ double d;
+ Note *n;
+
+ d = (b - 8192) / 4095.5;
+ d = pow(2, d / 12);
+ src->bend[ch] = d;
+ for(n = np.n; n != &np; n = n->n){
+ if(n->src != src || n->ch != ch)
+ continue;
+ f = SAMPLE / (440 * d * pow(1.05946, n->nt - 69));
+ n->f = f;
+ n->½f = f / 2;
+ }
+}
+
+void
+pop(Tracker *src, int ch, int nt)
+{
+ Note *n, *p;
+
+ for(p = &np, n = np.n; n != &np; p = n, n = n->n)
+ if(n->src == src && n->ch == ch && n->nt == nt){
+ p->n = n->n;
+ memset(n, 0, sizeof *n);
+ return;
+ }
+}
+
+void
+push(Tracker *src, int ch, int nt, int a)
+{
+ int f;
+ Note *n, *p;
+
+ for(p = &np, n = np.n; n != &np; p = n, n = n->n)
+ if(n->src == src && n->ch == ch && n->nt == nt){
+ n->a = a;
+ return;
+ }
+ for(n = nl; n < nl + nelem(nl); n++)
+ if(n->src == nil)
+ break;
+ if(n == nl + nelem(nl))
+ return;
+ n->src = src;
+ n->ch = ch;
+ n->nt = nt;
+ n->a = a;
+ f = SAMPLE / (440 * src->bend[ch] * pow(1.05946, nt - 69));
+ n->f = f;
+ n->½f = f / 2;
+ p->n = n;
+ n->n = &np;
+}
+
+void
readevent(Tracker *src)
{
uvlong l;
int n,t;
-
+
l = tconv(getvar(src));
run(src->t += l);
t = get8(src);
@@ -161,13 +221,12 @@
src->cmd = t;
switch(t >> 4){
case 0x8:
- n = get8(src);
+ pop(src, t & 15, get8(src));
get8(src);
- src->notes[t & 15][n] = 0;
break;
case 0x9:
n = get8(src);
- src->notes[t & 15][n] = get8(src);
+ push(src, t & 15, n, get8(src));
break;
case 0xB:
get16(src);
@@ -175,6 +234,11 @@
case 0xC:
get8(src);
break;
+ case 0xE:
+ n = get8(src) & 0x7f;
+ n = get8(src) << 7 & 0x3f80 | n;
+ bend(src, t & 15, n);
+ break;
case 0xF:
t = get8(src);
n = get8(src);
@@ -204,7 +268,7 @@
void
main(int argc, char **argv)
{
- int i, size;
+ int i, j, size;
uvlong t, mint;
Tracker *x, *minx;
@@ -228,9 +292,10 @@
size = get32(nil);
tr[i].data = emallocz(size);
read(fd, tr[i].data, size);
+ for(j = 0; j < 16; j++)
+ tr[i].bend[j] = 1.0;
}
- for(i = 0; i < 128; i++)
- freq[i] = SAMPLE / (440 * pow(1.05946, i - 69));
+ np.n = &np;
for(;;){
minx = nil;
mint = 0;