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.

**notice:** GitHub's Markdown formatter may break on this file as it doesn't seem to treat tables correctly.

# information

files may be zlib-compressed, but Furnace accepts uncompressed files as well.

all numbers are little-endian.

the following fields may be found in "size":
- `f` indicates a floating point number.
- `STR` is a UTF-8 zero-terminated string.
- `???` is an array of variable size.
- `S??` is an array of `STR`s.
- `1??` is an array of bytes.
- `2??` is an array of shorts.
- `4??` is an array of ints.

the format has changed several times across versions. a `(>=VER)` indicates this field is only present starting from format version `VER`, and `(<VER)` indicates this field is present only before version `VER`.

furthermore, an `or reserved` indicates this field is always present, but is reserved when the version condition is not met.

the `size of this block` fields represent the size of a block excluding the ID and the aforementioned field.
these fields are 0 in format versions prior to 100 (0.6pre1).

# format versions

the format versions are:

- 219: Furnace 0.6.7
- 218: Furnace 0.6.6
- 214: Furnace 0.6.5
- 212: Furnace 0.6.4
- 201: Furnace 0.6.3
- 197: Furnace 0.6.2
- 192: Furnace 0.6.1
- 181: Furnace 0.6
- 180: Furnace 0.6pre18
- 179: Furnace 0.6pre17
- 178: Furnace 0.6pre16
- 177: Furnace 0.6pre15
- 175: Furnace 0.6pre14
- 174: Furnace 0.6pre13
- 173: Furnace 0.6pre12
- 172: Furnace 0.6pre11
- 171: Furnace 0.6pre10
- 169: Furnace 0.6pre9
- 166: Furnace 0.6pre8
- 162: Furnace 0.6pre7
- 161: Furnace 0.6pre6
- 158: Furnace 0.6pre5
- 146: Furnace Pro (joke version)
- 143: Furnace 0.6pre4
- 141: Furnace Tournament Edition (for intro tune contest)
- 133: Furnace 0.6pre3
- 132: Furnace 0.6pre2
- 116: Furnace 0.6pre1.5
- 100: Furnace 0.6pre1
- 75: Furnace dev75/April Fools' 0.6pre0

- 54: Furnace 0.5.8
- 53: Furnace 0.5.7
- 52: Furnace 0.5.7pre4
- 51: Furnace 0.5.7pre3
- 50: Furnace 0.5.7pre2
- 49: Furnace 0.5.7pre1
- 48: Furnace 0.5.6
- 47: Furnace 0.5.6pre1
- 46: Furnace 0.5.5
- 45: Furnace 0.5.5pre3
- 44: Furnace 0.5.5pre2
- 43: Furnace 0.5.5pre1
- 42: Furnace 0.5.4
- 41: Furnace 0.5.3
- 40: Furnace 0.5.2
- 39: Furnace 0.5.2pre3
- 38: Furnace 0.5.2pre2
- 37: Furnace 0.5.2pre1
- 36: Furnace 0.5.1
- 35: Furnace 0.5
- 27: Furnace 0.4.6
- 26: Furnace 0.4.6pre1
- 25: Furnace 0.4.5
- 24: Furnace 0.4.4
- 23: Furnace 0.4.3
- 22: Furnace 0.4.2
- 21: Furnace 0.4.1
- 20: Furnace 0.4
- 19: Furnace 0.4pre3
- 18: Furnace 0.4pre2
- 17: Furnace 0.4pre1
- 16: Furnace 0.3.1
- 15: Furnace 0.3
- 14: Furnace 0.2.2
- 13: Furnace 0.2.1
- 12: Furnace 0.2

versions that do not appear in this list are `dev???` ones.

# header

the header is 32 bytes long.

```
size | description
-----|------------------------------------
 16  | "-Furnace module-" format magic
  2  | format version
  2  | reserved
  4  | song info pointer
  8  | reserved
```

# song info

```
size | description
-----|------------------------------------
  4  | "INFO" block ID
  4  | size of this block
  1  | time base (of first song)
  1  | speed 1 (of first song)
  1  | speed 2 (of first song)
  1  | initial arpeggio time (of first song)
  4f | ticks per second (of first song)
     | - 60 is NTSC
     | - 50 is PAL
  2  | pattern length (of first song)
     | - the limit is 256.
  2  | orders length (of first song)
     | - the limit is 256 (>=80) or 127 (<80).
  1  | highlight A (of first song)
  1  | highlight B (of first song)
  2  | instrument count
     | - the limit is 256.
  2  | wavetable count
     | - the limit is 256.
  2  | sample count
     | - the limit is 256.
  4  | pattern count (global)
 32  | list of sound chips
     | - possible soundchips:
     |   - 0x00: end of list
     |   - 0x01: YMU759 - 17 channels
     |   - 0x02: Genesis - 10 channels (compound!)
     |   - 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+SegaPCM) - 13 channels (compound!)
     |   - 0x09: Neo Geo CD (YM2610) - 13 channels
     |   - 0x42: Genesis extended - 13 channels
     |   - 0x43: SMS (SN76489) + OPLL (YM2413) - 13 channels (compound!)
     |   - 0x46: NES + VRC7 - 11 channels (compound!)
     |   - 0x47: C64 (6581) - 3 channels
     |   - 0x49: Neo Geo CD extended - 16 channels
     |   - 0x80: AY-3-8910 - 3 channels
     |   - 0x81: Amiga - 4 channels
     |   - 0x82: YM2151 - 8 channels
     |   - 0x83: YM2612 - 6 channels
     |   - 0x84: TIA - 2 channels
     |   - 0x85: VIC-20 - 4 channels
     |   - 0x86: PET - 1 channel
     |   - 0x87: SNES - 8 channels
     |   - 0x88: VRC6 - 3 channels
     |   - 0x89: OPLL (YM2413) - 9 channels
     |   - 0x8a: FDS - 1 channel
     |   - 0x8b: MMC5 - 3 channels
     |   - 0x8c: Namco 163 - 8 channels
     |   - 0x8d: YM2203 - 6 channels
     |   - 0x8e: YM2608 - 16 channels
     |   - 0x8f: OPL (YM3526) - 9 channels
     |   - 0x90: OPL2 (YM3812) - 9 channels
     |   - 0x91: OPL3 (YMF262) - 18 channels
     |   - 0x92: MultiPCM - 28 channels (UNAVAILABLE)
     |   - 0x93: Intel 8253 (beeper) - 1 channel
     |   - 0x94: POKEY - 4 channels
     |   - 0x95: RF5C68 - 8 channels
     |   - 0x96: WonderSwan - 4 channels
     |   - 0x97: Philips SAA1099 - 6 channels
     |   - 0x98: OPZ (YM2414) - 8 channels
     |   - 0x99: Pokémon Mini - 1 channel
     |   - 0x9a: AY8930 - 3 channels
     |   - 0x9b: SegaPCM - 16 channels
     |   - 0x9c: Virtual Boy - 6 channels
     |   - 0x9d: VRC7 - 6 channels
     |   - 0x9e: YM2610B - 16 channels
     |   - 0x9f: ZX Spectrum (beeper, tildearrow engine) - 6 channels
     |   - 0xa0: YM2612 extended - 9 channels
     |   - 0xa1: Konami SCC - 5 channels
     |   - 0xa2: OPL drums (YM3526) - 11 channels
     |   - 0xa3: OPL2 drums (YM3812) - 11 channels
     |   - 0xa4: OPL3 drums (YMF262) - 20 channels
     |   - 0xa5: Neo Geo (YM2610) - 14 channels
     |   - 0xa6: Neo Geo extended (YM2610) - 17 channels
     |   - 0xa7: OPLL drums (YM2413) - 11 channels
     |   - 0xa8: Atari Lynx - 4 channels
     |   - 0xa9: SegaPCM (for DefleMask compatibility) - 5 channels
     |   - 0xaa: MSM6295 - 4 channels
     |   - 0xab: MSM6258 - 1 channel
     |   - 0xac: Commander X16 (VERA) - 17 channels
     |   - 0xad: Bubble System WSG - 2 channels
     |   - 0xae: OPL4 (YMF278B) - 42 channels (UNAVAILABLE)
     |   - 0xaf: OPL4 drums (YMF278B) - 44 channels (UNAVAILABLE)
     |   - 0xb0: Seta/Allumer X1-010 - 16 channels
     |   - 0xb1: Ensoniq ES5506 - 32 channels
     |   - 0xb2: Yamaha Y8950 - 10 channels
     |   - 0xb3: Yamaha Y8950 drums - 12 channels
     |   - 0xb4: Konami SCC+ - 5 channels
     |   - 0xb5: tildearrow Sound Unit - 8 channels
     |   - 0xb6: YM2203 extended - 9 channels
     |   - 0xb7: YM2608 extended - 19 channels
     |   - 0xb8: YMZ280B - 8 channels
     |   - 0xb9: Namco WSG - 3 channels
     |   - 0xba: Namco C15 - 8 channels
     |   - 0xbb: Namco C30 - 8 channels
     |   - 0xbc: MSM5232 - 8 channels
     |   - 0xbd: YM2612 DualPCM extended - 11 channels
     |   - 0xbe: YM2612 DualPCM - 7 channels
     |   - 0xbf: T6W28 - 4 channels
     |   - 0xc0: PCM DAC - 1 channel
     |   - 0xc1: YM2612 CSM - 10 channels
     |   - 0xc2: Neo Geo CSM (YM2610) - 18 channels (UNAVAILABLE)
     |   - 0xc3: YM2203 CSM - 10 channels (UNAVAILABLE)
     |   - 0xc4: YM2608 CSM - 20 channels (UNAVAILABLE)
     |   - 0xc5: YM2610B CSM - 20 channels (UNAVAILABLE)
     |   - 0xc6: K007232 - 2 channels
     |   - 0xc7: GA20 - 4 channels
     |   - 0xc8: SM8521 - 3 channels
     |   - 0xc9: M114S - 16 channels (UNAVAILABLE)
     |   - 0xca: ZX Spectrum (beeper, QuadTone engine) - 5 channels
     |   - 0xcb: Casio PV-1000 - 3 channels
     |   - 0xcc: K053260 - 4 channels
     |   - 0xcd: TED - 2 channels
     |   - 0xce: Namco C140 - 24 channels
     |   - 0xcf: Namco C219 - 16 channels
     |   - 0xd0: Namco C352 - 32 channels (UNAVAILABLE)
     |   - 0xd1: ESFM - 18 channels
     |   - 0xd2: Ensoniq ES5503 (hard pan) - 32 channels (UNAVAILABLE)
     |   - 0xd4: PowerNoise - 4 channels
     |   - 0xd5: Dave - 6 channels
     |   - 0xd6: NDS - 16 channels
     |   - 0xd7: Game Boy Advance (direct) - 2 channels
     |   - 0xd8: Game Boy Advance (MinMod) - 16 channels
     |   - 0xd9: Bifurcator - 4 channels
     |   - 0xda: SCSP - 32 channels (UNAVAILABLE)
     |   - 0xdb: YMF271 (OPX) - 48 channels (UNAVAILABLE)
     |   - 0xdc: RF5C400 - 32 channels (UNAVAILABLE)
     |   - 0xdd: YM2612 XGM - 9 channels (UNAVAILABLE)
     |   - 0xde: YM2610B extended - 19 channels
     |   - 0xdf: YM2612 XGM extended - 13 channels (UNAVAILABLE)
     |   - 0xe0: QSound - 19 channels
     |   - 0xe1: PS1 - 24 channels (UNAVAILABLE)
     |   - 0xe2: C64 (6581) with PCM - 4 channels (UNAVAILABLE)
     |   - 0xe3: Watara Supervision - 4 channels (UNAVAILABLE)
     |   - 0xe4: µPD1771C - 1 channel (UNAVAILABLE)
     |   - 0xf0: SID2 - 3 channels
     |   - 0xf1: 5E01 - 5 channels
     |   - 0xf5: SID3 - 7 channels
     |   - 0xfc: Pong - 1 channel
     |   - 0xfd: Dummy System - 8 channels
     |   - 0xfe: reserved for development
     |   - 0xff: reserved for development
     | - (compound!) means that the system is composed of two or more chips,
     |   and has to be flattened.
     | - (UNAVAILABLE) means that the chip hasn't been implemented in Furnace
     |   yet.
 32  | sound chip volumes (<135) or reserved
     | - signed char, 64=1.0, 127=~2.0
     | - as of version 135 these fields only exist for compatibility reasons.
 32  | sound chip panning (<135) or reserved
     | - signed char, -128=left, 127=right
     | - as of version 135 these fields only exist for compatibility reasons.
 128 | sound chip flag pointers (>=119) or sound chip flags
     | - before 118, these were 32-bit flags.
     | - for conversion details, see oldflags.md.
 STR | song name
 STR | song author
  4f | A-4 tuning
  1  | limit slides (>=36) or reserved
  1  | linear pitch (>=36) or reserved
     | - 0: non-linear
     | - 1: only pitch change (04xy/E5xx) linear
     | - 2: full linear (>=94)
  1  | loop modality (>=36) or reserved
  1  | proper noise layout (>=42) or reserved
  1  | wave duty is volume (>=42) or reserved
  1  | reset macro on porta (>=45) or reserved
  1  | legacy volume slides (>=45) or reserved
  1  | compatible arpeggio (>=45) or reserved
  1  | note off resets slides (>=45) or reserved
  1  | target resets slides (>=45) or reserved
  1  | arpeggio inhibits portamento (>=47) or reserved
  1  | wack algorithm macro (>=47) or reserved
  1  | broken shortcut slides (>=49) or reserved
  1  | ignore duplicate slides (>=50) or reserved
  1  | stop portamento on note off (>=62) or reserved
  1  | continuous vibrato (>=62) or reserved
  1  | broken DAC mode (>=64) or reserved
  1  | one tick cut (>=65) or reserved
  1  | instrument change allowed during porta (>=66) or reserved
  1  | reset note base on arpeggio effect stop (0000) (>=69) or reserved
 4?? | pointers to instruments
 4?? | pointers to wavetables
 4?? | pointers to samples
 4?? | pointers to patterns
 ??? | orders (of first song)
     | - a table of bytes
     | - size=channels*ordLen
     | - read orders then channels
     | - the maximum value of a cell is FF (>=80) or 7F (<80).
 ??? | effect columns (of first song)
     | - size=channels
 1?? | channel hide status (of first song)
     | - size=channels
 1?? | channel collapse status (of first song)
     | - size=channels
 S?? | channel names (of first song)
     | - a list of channelCount C strings
 S?? | channel short names (of first song)
     | - same as above
 STR | song comment
  4f | master volume, 1.0f=100% (>=59)
     | this is 2.0f for modules before 59
 --- | **extended compatibility flags** (>=70)
  1  | broken speed selection
  1  | no slides on first tick (>=71) or reserved
  1  | next row reset arp pos (>=71) or reserved
  1  | ignore jump at end (>=71) or reserved
  1  | buggy portamento after slide (>=72) or reserved
  1  | new ins affects envelope (Game Boy) (>=72) or reserved
  1  | ExtCh channel state is shared (>=78) or reserved
  1  | ignore DAC mode change outside of intended channel (>=83) or reserved
  1  | E1xy and E2xy also take priority over Slide00 (>=83) or reserved
  1  | new Sega PCM (with macros and proper vol/pan) (>=84) or reserved
  1  | weird f-num/block-based chip pitch slides (>=85) or reserved
  1  | SN duty macro always resets phase (>=86) or reserved
  1  | pitch macro is linear (>=90) or reserved
  1  | pitch slide speed in full linear pitch mode (>=94) or reserved
  1  | old octave boundary behavior (>=97) or reserved
  1  | disable OPN2 DAC volume control (>=98) or reserved
  1  | new volume scaling strategy (>=99) or reserved
  1  | volume macro still applies after end (>=99) or reserved
  1  | broken outVol (>=99) or reserved
  1  | E1xy and E2xy stop on same note (>=100) or reserved
  1  | broken initial position of porta after arp (>=101) or reserved
  1  | SN periods under 8 are treated as 1 (>=108) or reserved
  1  | cut/delay effect policy (>=110) or reserved
  1  | 0B/0D effect treatment (>=113) or reserved
  1  | automatic system name detection (>=115) or reserved
     | - this one isn't a compatibility flag, but it's here for convenience...
  1  | disable sample macro (>=117) or reserved
  1  | broken outVol episode 2 (>=121) or reserved
  1  | old arpeggio strategy (>=130) or reserved
 --- | **virtual tempo data**
  2  | virtual tempo numerator of first song (>=96) or reserved
  2  | virtual tempo denominator of first song (>=96) or reserved
 --- | **additional subsongs** (>=95)
 STR | first subsong name
 STR | first subsong comment
  1  | number of additional subsongs
  3  | reserved
 4?? | pointers to subsong data
 --- | **additional metadata** (>=103)
 STR | system name
 STR | album/category/game name
 STR | song name (Japanese)
 STR | song author (Japanese)
 STR | system name (Japanese)
 STR | album/category/game name (Japanese)
 --- | **extra chip output settings (× chipCount)** (>=135)
  4f | chip volume
  4f | chip panning
  4f | chip front/rear balance
 --- | **patchbay** (>=135)
  4  | patchbay connection count
 4?? | patchbay
     | - see next section for more details.
  1  | automatic patchbay (>=136)
 --- | **a couple more compat flags** (>=138)
  1  | broken portamento during legato
  1  | broken macro during note off in some FM chips (>=155)
  1  | pre note (C64) does not compensate for portamento or legato (>=168)
  1  | disable new NES DPCM features (>=183)
  1  | reset arp effect phase on new note (>=184)
  1  | linear volume scaling rounds up (>=188)
  1  | legacy "always set volume" behavior (>=191)
  1  | reserved
 --- | **speed pattern of first song** (>=139)
  1  | length of speed pattern (fail if this is lower than 0 or higher than 16)
 16  | speed pattern (this overrides speed 1 and speed 2 settings)
 --- | **groove list** (>=139)
  1  | number of entries
 ??? | groove entries. the format is:
     | - 1 byte: length of groove
     | - 16 bytes: groove pattern
 --- | **pointers to asset directories** (>=156)
  4  | instrument directories
  4  | wavetable directories
  4  | sample directories
```

# patchbay

Furnace dev135 adds a "patchbay" which allows for arbitrary connection of chip outputs to system outputs.
it also allows connecting outputs to effects and so on.

a connection is represented as an unsigned int in the following format:

- bit 16-31: source port
- bit 0-15: destination port

a port is in the following format (hexadecimal): `xxxy`

- `xxx` (bit 4 to 15) represents a portset.
- `y` (bit 0 to 3) is the port in that portset.

reserved input portsets:
- `000`: system outputs
- `FFF`: "null" portset

reserved output portsets:
- `000` through `01F`: chip outputs
- `FFD`: wave/sample preview
- `FFE`: metronome
- `FFF`: "null" portset

# subsong

from version 95 onwards, Furnace supports storing multiple songs on a single file.
the way it's currently done is really weird, but it provides for some backwards compatibility (previous versions will only load the first subsong which is already defined in the `INFO` block).

```
size | description
-----|------------------------------------
  4  | "SONG" block ID
  4  | size 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
     | - the limit is 256.
  2  | orders length
     | - the limit is 256.
  1  | highlight A
  1  | highlight B
  2  | virtual tempo numerator
  2  | virtual tempo denominator
 STR | subsong name
 STR | subsong comment
 ??? | orders
     | - a table of bytes
     | - size=channels*ordLen
     | - read orders then channels
     | - the maximum value of a cell is FF.
 ??? | effect columns
     | - size=channels
 1?? | channel hide status
     | - size=channels
 1?? | channel collapse status
     | - size=channels
 S?? | channel names
     | - a list of channelCount C strings
 S?? | channel short names
     | - same as above
 --- | **speed pattern** (>=139)
  1  | length of speed pattern (fail if this is lower than 0 or higher than 16)
 16  | speed pattern (this overrides speed 1 and speed 2 settings)
```

# chip flags

```
size | description
-----|------------------------------------
  4  | "FLAG" block ID
  4  | size of this block
 STR | data
```

flags are stored in text (`key=value`) format. for example:

```
clock=4000000
stereo=true
```

# asset directories (>=156)

also known as "folder" in the user interface.

```
size | description
-----|------------------------------------
  4  | "ADIR" block ID
  4  | size of this block
  4  | number of directories
 --- | **asset directory** (×numberOfDirs)
 STR | name (if empty, this is the uncategorized directory)
  2  | number of assets
 1?? | assets in this directory
```

# instrument (>=127)

Furnace dev127 and higher use the new instrument format.

```
size | description
-----|------------------------------------
  4  | "INS2" block ID
  4  | size of this block
  2  | format version
  2  | instrument type
 ??? | features...
```

see [newIns.md](newIns.md) for more information.

# old instrument (<127)

instruments in older versions of Furnace used a different format. see [oldIns.md](oldIns.md) for more information.

## C64 compatibility note (>=187)

in Furnace dev187 the volume and cutoff macros have been separated, as noted above.
however, there are two other changes as well: **inverted relative (non-absolute) cutoff macro**; and a new, improved Special macro.

if version is less than 187, you must convert the Special macro:
1. do not continue if ex4 is not a Sequence type macro!
2. move bit 0 of ex4 macro data into bit 3.
3. set bit 0 on all steps of ex4 macro to 1.
4. if ex3 is not a Sequence type macro, stop here.
5. if ex3 macro length is 0, stop here.
6. merge the ex3 macro (former Special) into ex4 (former Test).
  - use the largest size (between ex3 and ex4).
  - if the ex3 macro is shorter than the ex4 one, use the last value of ex3, and vice-versa.
  - if the ex4 macro length is 0, expand it to the largest size, and set all steps to 1.

don't worry about loop or release...

# wavetable

```
size | description
-----|------------------------------------
  4  | "WAVE" block ID
  4  | size of this block
 STR | wavetable name
  4  | wavetable width
  4  | reserved
  4  | wavetable height
 4?? | wavetable data
```

# sample (>=102)

this is the new sample storage format used in Furnace dev102 and higher.

```
size | description
-----|------------------------------------
  4  | "SMP2" block ID
  4  | size of this block
 STR | sample name
  4  | length
  4  | compatibility rate
  4  | C-4 rate
  1  | depth
     | - 0: ZX Spectrum overlay drum (1-bit)
     | - 1: 1-bit NES DPCM (1-bit)
     | - 3: YMZ ADPCM
     | - 4: QSound ADPCM
     | - 5: ADPCM-A
     | - 6: ADPCM-B
     | - 7: K05 ADPCM
     | - 8: 8-bit PCM
     | - 9: BRR (SNES)
     | - 10: VOX
     | - 11: 8-bit μ-law PCM
     | - 12: C219 PCM
     | - 13: IMA ADPCM
     | - 14: 12-bit PCM (MultiPCM)
     | - 16: 16-bit PCM
  1  | loop direction (>=123) or reserved
     | - 0: forward
     | - 1: backward
     | - 2: ping-pong
  1  | flags (>=129) or reserved
     | - 0: BRR emphasis
  1  | flags 2 (>=159) or reserved
     | - 0: dither
     | - 1: no BRR filters (>=213)
  4  | loop start
     | - -1 means no loop
  4  | loop end
     | - -1 means no loop
 16  | sample presence bitfields
     | - for future use.
     | - indicates whether the sample should be present in the memory of a system.
     | - read 4 32-bit numbers (for 4 memory banks per system, e.g. YM2610
     |   does ADPCM-A and ADPCM-B on separate memory banks).
 ??? | sample data
     | - size is length
```

# old sample (<102)

this format is present when saving using previous Furnace versions.

```
size | description
-----|------------------------------------
  4  | "SMPL" block ID
  4  | size of this block
 STR | sample name
  4  | length
  4  | compatibility rate
  2  | volume (<58) or reserved
  2  | pitch (<58) or reserved
  1  | depth
     | - 0: ZX Spectrum overlay drum (1-bit)
     | - 1: 1-bit NES DPCM (1-bit)
     | - 3: YMZ ADPCM
     | - 4: QSound ADPCM
     | - 5: ADPCM-A
     | - 6: ADPCM-B
     | - 8: 8-bit PCM
     | - 9: BRR (SNES)
     | - 10: VOX
     | - 16: 16-bit PCM
  1  | reserved
  2  | C-4 rate (>=32) or reserved
  4  | loop point (>=19) or reserved
     | - -1 means no loop
 ??? | sample data
     | - version<58 size is length*2
     | - version>=58 size is length
```

# pattern (>=157)

```
size | description
-----|------------------------------------
  4  | "PATN" block ID
  4  | size of this block
  1  | subsong
  1  | channel
  2  | pattern index
 STR | pattern name (>=51)
 ??? | pattern data
     | - read a byte per row.
     | - if it is 0xff, end of data. the rest of the pattern is empty.
     | - if bit 7 is set, then skip N+2 rows. N is bits 0-6.
     |   - for example, $80 means skip 2 rows, $81 means skip 3, $82 means 4 and so on.
     | - if bit 7 is clear, then:
     |   - bit 0: note present
     |   - bit 1: ins present
     |   - bit 2: volume present
     |   - bit 3: effect 0 present
     |   - bit 4: effect value 0 present
     |   - bit 5: other effects (0-3) present
     |   - bit 6: other effects (4-7) present
     |   - if none of these bits are set, then skip 1 row.
     | - if bit 5 is set, read another byte:
     |   - bit 0: effect 0 present
     |   - bit 1: effect value 0 present
     |   - bit 2: effect 1 present
     |   - bit 3: effect value 1 present
     |   - bit 4: effect 2 present
     |   - bit 5: effect value 2 present
     |   - bit 6: effect 3 present
     |   - bit 7: effect value 3 present
     | - if bit 6 is set, read another byte:
     |   - bit 0: effect 4 present
     |   - bit 1: effect value 4 present
     |   - bit 2: effect 5 present
     |   - bit 3: effect value 5 present
     |   - bit 4: effect 6 present
     |   - bit 5: effect value 6 present
     |   - bit 6: effect 7 present
     |   - bit 7: effect value 7 present
     | - then read note, ins, volume, effects and effect values depending on what is present.
     | - for note:
     |   - 0 is C-(-5)
     |   - 179 is B-9
     |   - 180 is note off
     |   - 181 is note release
     |   - 182 is macro release
```


# old pattern (<157)

```
size | description
-----|------------------------------------
  4  | "PATR" block ID
  4  | size of this block
  2  | channel
  2  | pattern index
  2  | subsong (>=95) or reserved
  2  | reserved
 ??? | pattern data
     | - size: rows*(4+effectColumns*2)*2
     | - read shorts in this order:
     |   - note
     |     - 0: empty/invalid
     |     - 1: C#
     |     - 2: D
     |     - 3: D#
     |     - 4: E
     |     - 5: F
     |     - 6: F#
     |     - 7: G
     |     - 8: G#
     |     - 9: A
     |     - 10: A#
     |     - 11: B
     |     - 12: C (of next octave)
     |       - this is actually a leftover of the .dmf format.
     |     - 100: note off
     |     - 101: note release
     |     - 102: macro release
     |   - octave
     |     - this is an signed char stored in a short.
     |     - therefore octave value 255 is actually octave -1.
     |     - yep, another leftover of the .dmf format...
     |   - instrument
     |   - volume
     |   - effect and effect data (× effect columns)
     | - for note/octave, if both values are 0 then it means empty.
     | - for instrument, volume, effect and effect data, a value of -1 means empty.
 STR | pattern name (>=51)
```

# the Furnace wavetable format (.fuw)

similar to the instrument format...

```
size | description
-----|------------------------------------
 16  | "-Furnace waveta-" format magic
  2  | format version
  2  | reserved
```

wavetable data follows.