furnace/papers/format.md

the Furnace file format (.fur)

while Furnace works directly with the .dmf format, I had to create a new format to handle future additions to the program.

this document has the goal of detailing the format.

header

the header is 32 bytes long.

size	description
16	"-Furnace module-" format magic
2	format version
- should be 15 for Furnace 0.3
2	reserved
4	song info pointer
8	reserved

song info

size	description
4	"INFO" block ID
4	reserved
1	time base
1	speed 1
1	speed 2
1	initial arpeggio time
4f	ticks per second
- 60 is NTSC
- 50 is PAL
2	pattern length
2	orders length
1	highlight A
1	highlight B
2	instrument count
2	wavetable count
2	sample count
4	pattern count
32	list of sound chips
- possible soundchips:
- 0x00: end of list
- 0x01: YMU759 - 17 channels
- 0x02: Genesis - 10 channels
- 0x03: SMS (SN76489) - 4 channels
- 0x04: Game Boy - 4 channels
- 0x05: PC Engine - 6 channels
- 0x06: NES - 5 channels
- 0x07: C64 (8580) - 3 channels
- 0x08: Arcade (YM2151) - 13 channels
- 0x09: Neo Geo (YM2610) - 13 channels
- bit 6 enables alternate mode:
- 0x42: Genesis extended - 13 channels
- 0x47: C64 (6581) - 3 channels
- 0x49: Neo Geo extended - 16 channels
32	sound chip volumes
- signed char, 64=1.0, 127=~2.0
32	sound chip panning
- signed char, -128=left, 127=right
128	sound chip parameters (TODO)
???	song name
???	song author
24	reserved for compatibility flags
4??	pointers to instruments
4??	pointers to wavetables
4??	pointers to samples
4??	pointers to patterns
???	orders
- a table of shorts
- size=channels*ordLen
- read orders than channels
???	effect columns
- size=channels

instrument

size	description
4	"INST" block ID
4	reserved
2	format version (see header)
1	instrument type
- 0: standard
- 1: FM
- 2: Game Boy
- 3: C64
- 4: Amiga/sample
1	reserved
???	instrument name
---	FM instrument data
1	alg
1	feedback
1	fms
1	ams
1	operator count (always 4)
3	reserved
---	FM operator data × 4
1	am
1	ar
1	dr
1	mult
1	rr
1	sl
1	tl
1	dt2
1	rs
1	dt
1	d2r
1	ssgEnv
1	dam
1	dvb
1	egt
1	ksl
1	sus
1	vib
1	ws
1	ksr
12	reserved
---	Game Boy instrument data
1	volume
1	direction
1	length
1	sound length
---	C64 instrument data
1	triangle
1	saw
1	pulse
1	noise
1	attack
1	decay
1	sustain
1	release
2	duty
1	ring mod
1	osc sync
1	to filter
1	init filter
1	vol macro is cutoff
1	resonance
1	low pass
1	band pass
1	high pass
1	channel 3 off
2	cutoff
1	duty macro is absolute
1	filter macro is absolute
---	Amiga instrument data
2	initial sample
14	reserved
---	standard instrument data
4	volume macro length
4	arp macro length
4	duty macro length
4	wave macro length
4	volume macro loop
4	arp macro loop
4	duty macro loop
4	wave macro loop
1	arp macro mode
3	reserved
4??	volume macro
4??	arp macro
4??	duty macro
4??	wave macro

wavetable

size	description
4	"WAVE" block ID
4	reserved
???	wavetable name
4	wavetable size
4	wavetable min
4	wavetable max
4??	wavetable data

sample

size	description
4	"SMPL" block ID
4	reserved
???	sample name
4	length
4	rate
2	volume
2	pitch
1	depth
7	reserved
2??	sample data (always 16-bit)

pattern

size	description
4	"PATR" block ID
4	reserved
2	channel
2	pattern index
4	reserved
???	pattern data
- size: rows*(4+effectColumns*2)*2
- read shorts in this order:
- note
- octave
- instrument
- volume
- effect and effect data...