This section describes how to work with pages that have audio, including marking start and end times of the audio.
Narrative audio can be one long audio file or a series of clips. An audio editing tool can be used to mark the start and end time of a word or text phrase within an audio file, making it easier to define in an SMIL file.
Note: The following instructions show how to mark start and end times in an audio file using Audacity, a free, cross-platform audio editing tool. You can use another audio file tool to mark the start and end times in an audio file, however steps to do this will vary depending on the audio editing tool used.
To mark the start and end times in an audio file using Audacity:
Import the audio file.
Move the cursor to the desired start time.
Press Command-B to add a label to the cursor location.
Name the label using a naming convention with no spaces.
In the label track, drag the the right-side handle of the newly added marker to the end time. The label now represents a span, marking both the start and end time of a phrase.
To export one or more labels, go to File > Export Labels and save the labels as a text document.
Final audio files should be encoded following the standard Apple Books audio encoding guidelines. Audio tracks should be in stereo. Encode audio files as AAC at 256 kbps with .m4a as the file extension.
