Metadata chunks

Besides fmt and data, a WAV file can carry any number of optional chunks. They describe the audio without changing how it plays, and a reader that does not know one simply skips it.

Common chunks

Chunk	Holds	Defined by
`fact`	the number of sample frames, for compressed audio	Microsoft RIFF
`LIST` `INFO`	text tags: title, artist, comments, date, software	Microsoft RIFF
`cue`	markers at sample positions	Microsoft RIFF
`LIST` `adtl`	labels, notes and regions for the cue points	Microsoft RIFF
`smpl`	root note, tuning and loop points for samplers	MIDI Manufacturers Association
`bext`	broadcast details: description, originator, time reference, loudness	EBU, Broadcast Wave Format
`iXML`	production metadata from field recorders, as XML	the iXML specification
`id3`	an ID3v2 tag, as used in MP3 files	common practice
`JUNK`	reserved space, ignored by readers	Microsoft RIFF

Where they sit

Metadata chunks can come before or after the data chunk. Recorders often reserve room near the start with a JUNK chunk and fill it in later, while editors often write metadata after the samples so they can change it without moving the audio.

0RIFF WAVE12 bytes
1. 12fmt the format24 bytes
2. 36bext broadcast detailsvaries
3. …data the samplesvaries
4. …cue and LIST adtl markers and their labelsvaries
5. …LIST INFO tagsvaries

One possible order for a file with metadata on both sides of the samples.