APPLICATION is block type 2. It gives one application a place for its own data: a 32-bit application ID, which the application registers, and then that application’s bytes, as many as the block’s length leaves. Other software skips the block.
Registered application IDs
IANA keeps the registry of FLAC application metadata block IDs, on a first come, first served basis. The IDs are four bytes, usually printable ASCII, stored as a big-endian number.
| Value | ID | Application |
|---|---|---|
41544348 | ATCH | FlacFile |
42534F4C | BSOL | beSolo |
42554753 | BUGS | Bugs Player |
43756573 | Cues | GoldWave cue points |
44495343 | DISC | Red Book CD-DA LBA track layouts, TOC and CUE structures, verification logs and additional data for audio preservation |
46696361 | Fica | CUE Splitter |
46746F6C | Ftol | flac-tools |
4C414531 | LAE1 | LAE Lossy (LAEY) extension data |
4C414532 | LAE2 | LAE Lossless (LAES) extension data |
4D4F5442 | MOTB | MOTB MetaCzar |
4D505345 | MPSE | MP3 Stream Editor |
4D754D4C | MuML | MusicML: Music Metadata Language |
52494646 | RIFF | Sound Devices RIFF chunk storage |
5346464C | SFFL | Sound Font FLAC |
534F4E59 | SONY | Sony Creative Software |
5351455A | SQEZ | flacsqueeze |
54745776 | TtWv | TwistedWave |
55495453 | UITS | UITS Embedding tools |
61696666 | aiff | FLAC AIFF chunk storage |
696D6167 | imag | flac-image |
6B75756C | kuul | kuulo |
7065656D | peem | Parseable Embedded Extensible Metadata |
71667374 | qfst | QFLAC Studio |
72696666 | riff | FLAC RIFF chunk storage |
74756E65 | tune | TagTuner |
77363420 | w64 | FLAC Wave64 chunk storage (the fourth byte is a space) |
78626174 | xbat | XBAT |
786D6364 | xmcd | xmcd |
The aiff, riff and w64 IDs store the
chunks of the original AIFF, WAVE or Wave64 file so that decoding can restore it
exactly. What an application puts in its block is otherwise that application’s own
business, and the registry describes no layouts.