4.1 Reading metadata🔗ℹ

The returned handle is passed to the other procedures in this module. If the file cannot be opened, id3-tags still returns a handle, but tags-valid? returns #f. Other accessors then return their default values, such as "", -1, '(), or #f.

(define tags (id3-tags "song.mp3"))

(when (tags-valid? tags)

(printf "~a - ~a\n" (tags-artist tags) (tags-title tags)))

4.2 Common tag fields🔗ℹ

Composer and album artist return a list of strings when the property is present and the empty string when it is missing. The disc number is parsed from the first property value and defaults to -1. If the stored value cannot be parsed as a number, the result may be #f. Use tags-keys and tags-ref for direct access to the complete generic property store.

4.3 Audio properties🔗ℹ

4.4 Generic properties🔗ℹ

(for ([key (in-list (tags-keys tags))])

(printf "~a: ~s\n" key (tags-ref tags key)))

Generic properties may contain multiple values for a single key. The API keeps those values as lists instead of joining them into one string.

4.5 Embedded pictures🔗ℹ

The module represents embedded artwork as an opaque picture value. The picture value is returned by tags-picture and can be inspected with the picture procedures documented below. When no picture is available, the picture-related procedures return #f.

(define ext (tags-picture->ext tags))

(when ext

(tags-picture->file tags

(format "cover.~a" ext)))

4.6 Picture values🔗ℹ

4.7 Converting to a hash🔗ℹ

The hash is intended as a convenient snapshot for application code. Generic property values are not expanded into the hash; use tags-ref for those values.

4.8 Example🔗ℹ

(define tags (id3-tags "track.flac"))

(cond

[(not (tags-valid? tags))

(printf "No readable tags\n")]

[else

(printf "Title:  ~a\n" (tags-title tags))

(printf "Artist: ~a\n" (tags-artist tags))

(printf "Album:  ~a\n" (tags-album tags))

(printf "Length: ~a seconds\n" (tags-length tags))

(when (tags-picture tags)

(define ext (or (tags-picture->ext tags) 'bin))

(tags-picture->file tags (format "cover.~a" ext)))])

4.9 Implementation notes🔗ℹ

This chapter documents the public "taglib.rkt" layer. The native TagLib calls are delegated to "taglib-ffi.rkt", but callers normally should not use that lower level module directly.

The tag handle is implemented as a small Racket object with a private dispatch procedure. The native TagLib file is not stored in the handle. This keeps the public API simple and prevents native resources from leaking into application code.

The implementation normalizes generic property names by lower-casing TagLib property keys and converting them to symbols. Values remain lists of strings because TagLib properties may contain multiple values for one key.