FM voice loading, saving and conversion library

Code for loading and saving various FM voice formats meant for the Yamaha YM series of chips (OPL, OPM, OPN etc.), format autodetection code, and conversion between the various formats.

This library is meant to be used in fmtoy and vgm2x.

File Formats

Format	Type	Op	Max voices
INS	OPN	4	1
DMP	OPN	4	1
OPM	OPM	4	unlimited
TFI	OPN	4	1
Y12	OPN	4	1
SBI	OPL	2	1
INS	OPL	2	1
BNK	OPL	2	65536
IBK	OPL	2	128
CMF	OPL	2	128/256/65536

Structures

OPL

Field	Bit								Description
	7	6	5	4	3	2	1	0
ch_fb_cnt[0]	D	C	B	A	FB			CNT	Channel mask, feedback, connection
dam_dvb_ryt_bd_sd_tom_tc_hh	AM	VIB	RYT	BD	SD	TOM	TC	HH
am_vib_eg_ksr_mul	AM	VIB	EGT	KSR	MUL
ksl_tl	KSL		TL
ar_dr	AR				DR
sl_rr	SL				RR
ws						WS			Waveform select

Conversion

Conversion between OPL, OPM and OPN voices is only possible in some cases, in other cases it involves approximation, and in others it is not possible.

OPM files

Reading:

uint8_t *data; // Have your data in this buffer
size_t data_len; // with this length
struct opm_file opm;
int r = opm_file_load(&opm, data, data_len);
if(r != OPM_FILE_SUCCESS) {
	fprintf(stderr, "Could not load file: %s (%d)\n", opm_file_error_string(r), r);
	exit(1);
}

Writing:

size_t write_fn(void *buf, size_t bufsize, void *data_ptr) {
	FILE *f = (FILE *)data_ptr;
	return fwrite(buf, 1, bufsize, f);
}

struct opm_file opm;
opm_file_init(&opm);

FILE *f = fopen("out.opm", "w");
int opm_file_save(&opm, write_fn, f);
fclose(f);

Building with emscripten

emmake make libfmvoice.a