RMI file embedded SoundFont bank

The SF2 RMIDI extension lets an RMI file carry a SoundFont 2 bank, a nested RIFF chunk whose form type is sfbk. It holds a preset’s sounds and how they are played. An SF3 bank is the same layout with the samples compressed as Vorbis. All numbers are little-endian. The fields here are those of the SoundFont 2.04 specification; see the INFO entries for how the bank offset applies.

Structure

RIFF 'sfbk'
  LIST INFO     names and versions
  LIST sdta     smpl (samples), sm24 (low bytes, optional)
  LIST pdta     phdr pbag pmod pgen inst ibag imod igen shdr

The three lists of a SoundFont bank

LIST INFO

ID	Meaning
`ifil`	The SoundFont version: major and minor, u16 each
`isng`	The target sound engine
`INAM`	The bank’s name
`irom`	The sound ROM the bank uses
`iver`	The ROM version: major and minor
`ICRD`, `IENG`, `IPRD`, `ICOP`, `ICMT`, `ISFT`	Creation date, designers, product, copyright, comments, software

Sample data (sdta)

smpl holds every sample’s data as 16-bit little-endian numbers, each sample followed by at least 46 zero samples, so that interpolation runs off cleanly. sm24, new in 2.04, has one low byte for each sample, making them 24-bit. In an SF3 bank a sample’s data is Vorbis and its header’s start and end count bytes.

Tables (pdta)

Nine tables of fixed-size records. Each ends with a terminal record that only marks where the one before it stops.

Chunk	Record	Size	Fields
`phdr`	Preset	38	Name (20 chars), preset, bank (128 is drums), first zone (`pbag`), then library, genre, morphology, which are reserved
`pbag`	Preset zone	4	First generator, first modulator
`pmod`	Preset modulator	10	See below
`pgen`	Preset generator	4	Generator number, amount
`inst`	Instrument	22	Name (20 chars), first zone (`ibag`)
`ibag`	Instrument zone	4	First generator, first modulator
`imod`	Instrument modulator	10	See below
`igen`	Instrument generator	4	Generator number, amount
`shdr`	Sample	46	Name (20 chars), start, end, loop start, loop end (u32, in samples), sample rate, original key, pitch correction (cents, signed), sample link, sample type

Sample type

1 mono, 2 right, 4 left, 8 linked; the top bit, 8000, marks a sample held in ROM. 10 is added in SF3 for a Vorbis sample.

Generators

A generator sets one sound parameter. The amount is a signed 16-bit number, except ranges (keyRange, velRange), a low and a high byte. Units are samples (smpls), cents, decibels × 10 (cB) and timecents (1200 per octave of time).

#	Generator	#	Generator	#	Generator
0	startAddrsOffset	21	delayModLFO	42	reserved1
1	endAddrsOffset	22	freqModLFO	43	keyRange
2	startloopAddrsOffset	23	delayVibLFO	44	velRange
3	endloopAddrsOffset	24	freqVibLFO	45	startloopAddrsCoarseOffset
4	startAddrsCoarseOffset	25	delayModEnv	46	keynum
5	modLfoToPitch	26	attackModEnv	47	velocity
6	vibLfoToPitch	27	holdModEnv	48	initialAttenuation
7	modEnvToPitch	28	decayModEnv	49	reserved2
8	initialFilterFc	29	sustainModEnv	50	endloopAddrsCoarseOffset
9	initialFilterQ	30	releaseModEnv	51	coarseTune
10	modLfoToFilterFc	31	keynumToModEnvHold	52	fineTune
11	modEnvToFilterFc	32	keynumToModEnvDecay	53	sampleID
12	endAddrsCoarseOffset	33	delayVolEnv	54	sampleModes (0 no loop, 1 loop, 3 loop until release)
13	modLfoToVolume	34	attackVolEnv	55	reserved3
14	unused1	35	holdVolEnv	56	scaleTuning
15	chorusEffectsSend	36	decayVolEnv	57	exclusiveClass
16	reverbEffectsSend	37	sustainVolEnv	58	overridingRootKey
17	pan	38	releaseVolEnv	59	unused5
18	unused2	39	keynumToVolEnvHold	60	endOper
19	unused3	40	keynumToVolEnvDecay
20	unused4	41	instrument

Modulators

A modulator record is five 16-bit fields: source, destination generator (top bit set for another modulator), amount (signed), amount source, transform (0 linear, 2 absolute value). A source is a controller and how it is read:

Bits	Meaning
0–6	The index: a MIDI controller number when bit 7 is set, otherwise a general controller: 0 none, 2 note-on velocity, 3 note-on key number, 10 poly pressure, 13 channel pressure, 14 pitch wheel, 16 pitch wheel sensitivity, 127 link
7	Set for a MIDI controller
8	Direction: 0 min to max, 1 max to min
9	Polarity: 0 unipolar, 1 bipolar
10–15	Curve: 0 linear, 1 concave, 2 convex, 3 switch

In the explorer

The bank’s lists and tables are nodes, with every field named. Presets, instruments and samples appear as tables, and each sample can be opened as a WAV file, or an Ogg Vorbis file in an SF3 bank. No RMI file with a bank was among those examined for this site, so the reading is tested on files built to this layout.

.RMI File Format – Embedded SoundFont bank