Reads the ID3 tag of an MP3 file, or the one a wave file holds in an "id3 " chunk. Versions 2.2, 2.3 and 2.4 are read, as is the older version 1 tag at the end of a file where there is no version 2 tag to read instead. A file holding no tag gives an empty result rather than an error.
Details
Fields are named by the identifiers the frames themselves carry, such as
TIT2 for a title, TPE1 for an artist and COMM for a comment, rather
than being renamed, so that a frame this package has never heard of reads as
readily as the ones it has. A frame that carries a description, which is any
comment or user-defined frame, is named by it as well, as in
TXXX|Recordist; a name that would otherwise repeat gets a number, as in
COMM.2. A version 1 tag has no frames and its fields are named title,
artist, album, year, comment, track and genre, the last being
the numeric code the format defines rather than its name.
The version of the tag is kept on the result as its "version" attribute. The languages of any frames that declared one are kept as "languages", and the sizes of the frames whose values this package does not read, which is artwork, counters, identifiers and anything else that is not text, as "skipped".
Text declared as ISO-8859-1 that is in fact valid UTF-8 is read as UTF-8, which is what xeno-canto writes into the comment frame of its recordings.
A version 1 tag is marked by nothing more than the three letters "TAG" at a fixed distance from the end of the file, which the audio of a wave file can spell by chance, so one is only looked for in an MP3 file or in a file of no format this package recognises. A wave file keeps its tag in a chunk, where there is no guessing involved.
References
Nilsson, M. (2000). ID3 tag version 2.4.0. https://id3.org/id3v2.4.0-structure
See also
readMetadata() reads this and every other metadata format a file
carries at once.
Examples
if (FALSE) { # \dontrun{
m <- id3("XC428067.mp3")
m[["TIT2"]]
attr(m, "version")
} # }