SoundfontStudies

A library that can load Soundfont (.sf2) files, and format it neatly so it can be used in applications like a software sampler.

Features

• 16-bit sample loading
• Full preset parsing, including all the preset and instrument zones

How to use

• Add the common.h, soundfont.h, soundfont.cpp, and structs.h files to your project. In what folder the files are exactly is not important, but make sure all those files are in the same folder together.
• Quick example to load a soundfont:

int main() {
	// You can do this...
	Flan::Soundfont soundfont1("path/to/soundfont.sf2");
	
	// ...or, alternatively this
	Flan::Soundfont soundfont2;
	soundfont2.from_file("path/to/soundfont.sf2");
}

Known issues

• None! Please report if you find any.

Future plans

• Single header file?

Data structures

The Soundfont struct exposes two fields:

std::map<u16, Preset> presets;
std::vector<Sample> samples;

Sample

A Sample is a data structure that contains:

• A pointer to raw 16-bit signed PCM sample data
• A pointer to the linked sample's 16-bit signed PCM sample data
• A base sample rate (original root key and fine tuning are already applied here)
• The length of the sample
• The loop start and loop end of the sample
• The sample type (used to see if it's mono, the left channel, or the right channel)

Preset

A Preset is a data structure that only contains a list of Zone, a collection of settings meant for a sampler to use.
The map is indexed by a u16, with the bank number in the high byte, and the preset number in the low byte.

Zone

A Zone is a collection of settings meant for a software sampler. It has:

• Key range
• Velocity range
• Index of the sample (used to index the Sample array in Soundfont)
• Sample start, end, loop start, and loop end offsets (some soundfonts, notably the ones VGMtrans export use this a lot)
• Root key offset, relative to the Sample's root key
• Sample loop enable flag
• Stereo panning
• Volume envelopes: Delay, Attack, Hold, Decay, Sustain, and Release values. All in either 1.0 / time in seconds, volume in dB or dB per second (note: usually 6 dB = 0.5x)
• Tuning scale: how many semitones there are between each MIDI key
• Initial attenuation: volume in dB to subtract from zone volume (note: usually 15 dB = 0.5x)

To determine which zones to use when playing a note, there are key ranges and velocity ranges. For a given Preset, you can loop over each Zone, check if the midi key and velocity are in-between or equal to those range values, and if they are, that zone should be used for that note.