SoundFont3

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SoundFont 2.04 Specification ​

Purpose

To understand the library API according to SoundFont 2.04 specification.

This section will alternate between specification summary and API documentation.

SoundFonts are RIFF files containing WAV samples, preset information and metadata. SoundFonts interact with MIDI to create a sound.

What is RIFF ​

RIFF is like JSON but binary - store nested binaries. It is a standard for other file formats like WAV.

Data is stored in chunks with metadata:

C
char[4]            chunkId =      "RIFF"; // 4 byte
uint32_t           chunkBytes =   21772728; // 4 byte
char[4]            format         "sfbk"; // 4 byte if subchunk exists
byte[chunkBytes]   chunkData =    <anotherChunk>;
  • chunkId is a four-character code (FourCC) totalling 4 bytes.
    • Only trunk chunks with id RIFF and LIST can have subchunks, hence 12 byte metadata.
    • Leaf chunks have 8 byte metadata since format is not required.
  • chunkBytes is the amount of bytes in a chunk.
  • format specifies format type since chunkId is already used for tracking subchunks.
  • chunkData could be a a subchunk or contain data.
  • All chunks must contain even number of bytes.

SoundFont RIFF structure ​

Every SoundFont2 contain three nested top chunks:

ChunkId RIFF, format sfbk - RIFF file declaration

  • ChunkId LIST
  • Format INFO
  • Contains SoundFont3.metadata and:
    • ChunkId LIST
    • Format sdta
    • Contains SoundFont3.sampleData and:
      • ChunkId LIST
      • Format pdta
      • Contains SoundFont3.presetData

Raw SoundFont RIFF chunks are accessed through SoundFont3.chunk.

Metadata ​

Accessible thorugh SoundFont3.metaData

  • ifil - SoundFont version - SoundFont3.metaData.version

  • isng - Sound engine - SoundFont3.metaData.soundEngine

  • INAM - SoundFont bank - SoundFont3.metaData.name

    The other leaf chunks are optional

  • irom - Sound ROM samples reference - SoundFont3.metaData.rom

  • iver - Sound ROM revision - SoundFont3.metaData.romVersion

  • ICRD - Creation mm/dd/yy - SoundFont3.metaData.creationDate

  • IENG - SoundFont author - SoundFont3.metaData.author

  • IPDR - For this product - SoundFont3.metaData.product

  • ICOP - Copyright - SoundFont3.metaData.copyright

  • ICMT - Comments - SoundFont3.metaData.comments

  • ISFT - Tool created SoundFont - SoundFont3.metaData.createdBy

Sample data ​

  • smpl - 16-bit WAV - SoundFont3.sampleData

  • sm24 - Plus 8-bit WAV

Preset data ​

Available through SoundFont3.presetData

Preset metadata:

  • phdr - Headers - SoundFont3.presetData.presetHeaders

  • pbag - Zone indices - SoundFont3.presetData.presetZones

  • pmod - Modulators - SoundFont3.presetData.presetModulators

  • pgen - Generators - SoundFont3.presetData.presetGenerators

Instrument metadata:

  • inst - Headers - SoundFont3.presetData.instrumentHeaders

  • ibag - Zone indices - SoundFont3.presetData.instrumentZones

  • imod - Modulators - SoundFont3.presetData.instrumentModulators

  • igen - Generators - SoundFont3.presetData.instrumentGenerators

Sample metadata:

  • shdr - Headers - SoundFont3.presetData.sampleHeaders