furnace/papers/format.md

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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 1 for Furnace 0.2
2 reserved
4 song info pointer
8 reserved

song info

size description
4 "INFO" block ID
4 length of this block
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
1 sound chip count
31 list of sound chips
- possible soundchips:
- 0x00: invalid - 0 channels
- 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
4 reserved
124 sound chip parameters (TODO)
4 pointer song name
4 pointer to 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
??? effect columns
- size=channels

instrument

size description
4 "INST" block ID
4 length of this block
2 format version (see header)
1 instrument type
- 0: standard
- 1: FM
- 2: Game Boy
- 3: C64
- 4: Amiga/sample
1 reserved
4 pointer to 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 length of this block
4 pointer to wavetable name
4 wavetable size
4 wavetable min
4 wavetable max
4?? wavetable data

sample

size description
4 "SMPL" block ID
4 length of this block
4 pointer to 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 length of this block
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...