Audio Source Profile

The audiobook is delivered as an "album" and the <album_type> is audiobook to distinguish it from other content types. In the XML for the audiobook, the <album> tag represents the audiobook and the <track> tag within the <album> tag is used to deliver the track audio file. In this document, the term "track audio file" refers to an audio file that is less than 23 hours in length and it is delivered within one <track> tag. One <track> contains one audio file (see the following paragraphs for examples on how to handle longer audiobooks).

A track audio file can be a maximum of 23 hours in duration. Note that the 23-hour limit applies to one track; for longer audiobooks, you can deliver multiple tracks, and each track can be up to 23 hours long. If a single track audio file is longer than 23 hours, delivery will fail.

Keep the following in mind when delivering audiobook audio files:

• Track audio files must have the same bit rate throughout; any variance may cause an error when the delivered package is processed by Apple.

• If the duration of the audiobook is less than 23 hours, it must be delivered as a single track.

• If the duration of the audiobook is 23 hours or longer, it must be delivered in multiple tracks.

• When delivering multiple tracks, use the smallest possible number of tracks that adhere to the following requirements:

  • Each track must be under 23 hours in duration.

  • For books with multiple tracks, each track must be no less than 60 minutes in duration.

  • Audiobooks must consist of no more than 25 tracks.

  • Chapters must not span track boundaries.

Apple Books accepts audio with a sampling rate of 22.05kHz and 16-bit or greater or 96Khz with 24-bit resolution.

Track audio files must be provided in one of the audio formats in the table below, and must use the filename extension corresponding to the provided format.