FFE file format: Effect list

Each effect is a LIST chunk of type efct. What is inside is a DirectInput DIEFFECT structure written out with its pointers turned into flags, so that the arrays they pointed to could follow as data chunks. The offsets below count from the first byte of the LIST chunk. Numbers are little-endian.

Layout

+0x00List header LIST, the size, efct12
+0x0CName64
+0x4CDIEFFECT56
+0x84Effect type GUID16
+0x94A number4
+0x98Data chunks axes, direction, envelope, parametersto the end of the list

One effect list.

Offset	Size	Name	Description
`+0x00`	4	List ID	`LIST`.
`+0x04`	4	List size	The bytes after this field: the rest of the effect. In every file seen the lists of a file add up exactly to the end of the file.
`+0x08`	4	List type	`efct`.
`+0x0C`	64	Name	The effect’s name as a zero-ended string in a 64-byte buffer, such as `ConstantForce10` or `Sine6`. Force Editor does not clear the buffer, so what follows the zero is left over from whatever was in it before: in `shotgun1.ffe` the second effect’s buffer reads `Sine85`, a zero, then `tForce10`, the tail of the `ConstantForce10` that was there before, and after that come bytes that look like leftover memory. All 262 names have such bytes after the zero; ignore them.
`+0x4C`	56	DIEFFECT	See below.
`+0x84`	16	Effect type	The GUID of the effect type, for example `GUID_Sine`. The standard ones are on the effect types page. This is the `GuidEffect` that `DIFILEEFFECT` hands to a program.
`+0x94`	4	A number	`1` in all 262 effects seen. What it means is not known: it could be a version or a count.
`+0x98`		Data chunks	Up to four `data` chunks, in the order below.

The DIEFFECT

The 14 DWORDs of the DIEFFECT structure of DirectInput 7 (dinput.h), in order. The four fields that were pointers in memory hold, in the file, the DIEP_* flag of the data chunk that holds what they pointed to, or 0 when there is none.

Offset	Field	Description
`+0x4C`	`dwSize`	56, the size of `DIEFFECT`.
`+0x50`	`dwFlags`	`DIEFF_*` flags: how the axes and direction are given. `0x01` `DIEFF_OBJECTIDS` (axes are object IDs), `0x02` `DIEFF_OBJECTOFFSETS` (axes are offsets in the data format), `0x10` `DIEFF_CARTESIAN`, `0x20` `DIEFF_POLAR`, `0x40` `DIEFF_SPHERICAL`. All 262 effects have `0x22`: offsets and polar.
`+0x54`	`dwDuration`	How long the effect lasts, in microseconds, or `0xFFFFFFFF` (`INFINITE`) to play until stopped. 5 effects are infinite.
`+0x58`	`dwSamplePeriod`	The time between the device’s updates of the effect, in microseconds. 0 (the default) in every effect.
`+0x5C`	`dwGain`	The effect’s gain, up to 10000 (full strength). 10000 in every effect.
`+0x60`	`dwTriggerButton`	The button that plays the effect, or `0xFFFFFFFF` (`DIEB_NOTRIGGER`) for none. With `DIEFF_OBJECTOFFSETS` it is the button’s offset in the data format: `0x30` is `DIJOFS_BUTTON0`, which 23 effects have.
`+0x64`	`dwTriggerRepeatInterval`	The time between repeats while the trigger is held, in microseconds. `0xFFFFFFFF` in every effect.
`+0x68`	`cAxes`	The number of axes: 2 in every effect.
`+0x6C`	`rgdwAxes`	`0x20` (`DIEP_AXES`): an axes chunk follows. The explorer accepts 0 (none) or 0x20.
`+0x70`	`rglDirection`	`0x40` (`DIEP_DIRECTION`): a direction chunk follows.
`+0x74`	`lpEnvelope`	`0x80` (`DIEP_ENVELOPE`) when there is an envelope chunk, 0 for none. 75 effects have one.
`+0x78`	`cbTypeSpecificParams`	The size in bytes of the effect type’s parameters: 4 for a constant force, 8 for a ramp, 16 for a wave, 24 for each axis of a condition.
`+0x7C`	`lpvTypeSpecificParams`	`0x100` (`DIEP_TYPESPECIFICPARAMS`): a parameters chunk follows.
`+0x80`	`dwStartDelay`	The time between the effect being started and its force beginning, in microseconds. Added in DirectInput 6, so the structure is 56 bytes and not the 52 of `DIEFFECT_DX5`. 131 effects have a delay.

The data chunks

Each is an ordinary chunk: data, a 32-bit size, and the bytes. A chunk is there when the matching flag above is not 0, and they follow in this order.

Chunk	When	Size	Contents
Axes	`rgdwAxes` is not 0	4 × `cAxes`	One DWORD for each axis. With `DIEFF_OBJECTOFFSETS` they are offsets in the device’s data format: 0 X, 4 Y, 8 Z, 12 X rotation, 16 Y rotation, 20 Z rotation, 24 and 28 the sliders. The files all have 0 and 4.
Direction	`rglDirection` is not 0	4 × `cAxes`	One signed number for each axis. In polar coordinates the first is the angle in hundredths of a degree (0 north, 9000 east, 18000 south) and the second is 0; in Cartesian they are the components of a vector.
Envelope	`lpEnvelope` is not 0	20	A `DIENVELOPE`: `dwSize` (20), `dwAttackLevel`, `dwAttackTime`, `dwFadeLevel`, `dwFadeTime`. The levels are 0 to 10000, the times microseconds.
Parameters	`cbTypeSpecificParams` is not 0	`cbTypeSpecificParams`	The effect type’s own structure: see effect types.

An envelope changes the strength of the effect over time: it starts at the attack level, rises to the effect’s full strength over the attack time, and over the last fade time falls to the fade level. Force curves shows how the explorer draws it.

Worked example

chainb.ffe from the DirectX 7 SDK has one effect, a sine wave named Sine6 with an envelope. The file is 264 bytes: 28 for the header and 236 for the list.

Offset	Bytes	Meaning
`0x00`	`52 49 46 46`	`RIFF`
`0x04`	`00 00 00 00`	RIFF size, 0
`0x08`	`46 4F 52 43`	`FORC`
`0x0C`	`5C 77 7E 19 BA 34 D3 11 AB D5 00 C0 4F 8E C6 27`	File GUID {197E775C-34BA-11D3-ABD5-00C04F8EC627}
`0x1C`	`4C 49 53 54`	`LIST`
`0x20`	`E4 00 00 00`	List size 228 (0x1C + 8 + 228 = 264)
`0x24`	`65 66 63 74`	`efct`
`0x28`	`53 69 6E 65 36 00` and 58 more bytes	Name “Sine6”, then left-over bytes to the end of the 64
`0x68`	`38 00 00 00`	`dwSize` 56
`0x6C`	`22 00 00 00`	`dwFlags` 0x22: offsets and polar
`0x70`	`88 6C 06 00`	`dwDuration` 0x66C88 = 421000 µs
`0x74`	`00 00 00 00`	`dwSamplePeriod` 0
`0x78`	`10 27 00 00`	`dwGain` 10000
`0x7C`	`FF FF FF FF`	`dwTriggerButton` none
`0x80`	`FF FF FF FF`	`dwTriggerRepeatInterval`
`0x84`	`02 00 00 00`	`cAxes` 2
`0x88`	`20 00 00 00`	`rgdwAxes`: DIEP_AXES
`0x8C`	`40 00 00 00`	`rglDirection`: DIEP_DIRECTION
`0x90`	`80 00 00 00`	`lpEnvelope`: DIEP_ENVELOPE
`0x94`	`10 00 00 00`	`cbTypeSpecificParams` 16
`0x98`	`00 01 00 00`	`lpvTypeSpecificParams`: DIEP_TYPESPECIFICPARAMS
`0x9C`	`38 C7 00 00`	`dwStartDelay` 51000 µs
`0xA0`	`23 1C 54 13 33 8E D0 11 9A D0 00 A0 C9 A0 6E 35`	Effect type {13541C23-8E33-11D0-9AD0-00A0C9A06E35}, `GUID_Sine`
`0xB0`	`01 00 00 00`	The number, 1
`0xB4`	`64 61 74 61 08 00 00 00 00 00 00 00 04 00 00 00`	`data`, 8 bytes: axes 0 (X) and 4 (Y)
`0xC4`	`64 61 74 61 08 00 00 00 00 00 00 00 00 00 00 00`	`data`, 8 bytes: direction 0 and 0 (north)
`0xD4`	`64 61 74 61 14 00 00 00 14 00 00 00 40 1F 00 00 74 A4 00 00 88 13 00 00 D0 91 02 00`	`data`, 20 bytes: envelope with size 20, attack level 8000, attack time 42100 µs, fade level 5000, fade time 168400 µs
`0xF0`	`64 61 74 61 10 00 00 00 88 13 00 00 00 00 00 00 00 00 00 00 02 7E 00 00`	`data`, 16 bytes: a `DIPERIODIC` with magnitude 5000, offset 0, phase 0 and period 32258 µs

That is a 31 Hz sine wave of half strength, played for 0.42 seconds after a 51 millisecond delay. The envelope starts it at a level of 8000 and brings it down to its magnitude of 5000 over 42 milliseconds; the fade level equals the magnitude, so the end of the effect does not fade. The list ends at byte 0x108, the end of the file.

.FFE File Format – Effect list

Layout

The DIEFFECT

The data chunks

Worked example