A wave file is a sequence of chunks, each named by four characters, and what a recorder or an editor wrote into one is what the readers in this package go looking for. This reports the chunks themselves: every chunk the file holds, in the order it holds them, whether or not anything here can read it.
Value
A data frame of one row per chunk, with the chunk's identifier, the
one-based position of the first byte of its body, its size in bytes,
whether it was truncated, and, for a LIST chunk, the kind of list it is.
The form of the file, its RIFF size and the path it was read from are
attached as attributes.
Details
Only the chunk headers are read, each seeking past the body it describes, so listing the chunks of a recording costs the same whether it is a second long or an hour. Reading the file as a path is the cheaper way round for that reason; a raw vector is walked where it sits.
A chunk whose declared size runs past the end of the file is reported with
the size it actually has and flagged as truncated, rather than refused, as
recordings cut short by a flat battery or a full card are common. A file over
4 GiB written in the RF64 or BW64 form is walked by the sizes in its ds64
chunk, as readAudio() reads it.
Examples
f <- system.file("extdata", "AUDIOMOTH_GUANO.WAV", package="sonicscrewdriver")
wavChunks(f)
#> RIFF WAVE, 4 chunks
#> id start size truncated form
#> 1 fmt 21 16 FALSE <NA>
#> 2 LIST 45 436 FALSE INFO
#> 3 data 489 1600 FALSE <NA>
#> 4 guan 2097 358 FALSE <NA>
# The chunks nothing in this package reads are listed too, so a file can be
# looked at before a reader for it exists.
chunks <- wavChunks(f)
chunks[!chunks$id %in% c("fmt ", "data"), ]
#> RIFF WAVE, 2 chunks
#> id start size truncated form
#> 2 LIST 45 436 FALSE INFO
#> 4 guan 2097 358 FALSE <NA>