ref: b0a059537147237e868b4a8f07922ae8a349e55c
dir: /sys/src/games/midi/midi.c/
#include <u.h> #include <libc.h> #include <bio.h> #include "midifile.h" typedef struct{ uchar notes[Nchan][128]; } Notes; int freq[128]; uchar outbuf[IOUNIT], *outp = outbuf; void samp(double n) { int i, j, f, v, ns, no[128]; short u; Track *t; Notes *nn; static double Δ, ε; static uvlong τ; Δ = delay(n) + ε; ns = Δ; ε = Δ - ns; if(ns <= 0) return; memset(no, 0, sizeof no); for(t=tracks; t<tracks+ntrk; t++){ if(t->ended) continue; nn = t->aux; for(i=0; i<Nchan; i++) for(j=0; j<128; j++) no[j] += nn->notes[i][j]; } while(ns-- > 0){ v = 0; for(j=0; j<128; j++){ f = (τ % freq[j]) >= freq[j]/2 ? 1 : 0; v += f * no[j]; } u = v * 10; outp[0] = outp[2] = u; outp[1] = outp[3] = u >> 8; outp += 4; if(outp == outbuf + sizeof outbuf){ Bwrite(outbf, outbuf, sizeof outbuf); outp = outbuf; } τ++; } } void event(Track *t) { int e, c; Msg msg; Notes *nn; e = nextev(t); translate(t, e, &msg); c = msg.chan - chan; nn = t->aux; switch(msg.type){ case Cnoteoff: nn->notes[c][msg.arg1] = 0; break; case Cnoteon: nn->notes[c][msg.arg1] = msg.arg2; break; } } void main(int argc, char **argv) { int i, cat; Track *t; cat = 0; ARGBEGIN{ case 'D': trace = 1; break; case 'c': cat = 1; break; }ARGEND; initmid(); if(readmid(*argv) < 0) sysfatal("readmid: %r"); for(i=0; i<128; i++) freq[i] = samprate / (440 * pow(1.05946, i - 69)); for(t=tracks; t<tracks+ntrk; t++) t->aux = emalloc(sizeof(Notes)); outbf = cat ? efdopen(1, OWRITE) : eopen("/dev/audio", OWRITE); evloop(); Bwrite(outbf, outbuf, outp - outbuf); Bterm(outbf); exits(nil); }