This specification describes the requirements for the creation of audiobooks, using a profile of the Publication Manifest specification.
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This section describes the status of this document at the time of its publication. Other documents
may supersede this document. A list of current W3C
publications and the latest revision of this technical report can be found in the W3C technical
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A W3C Recommendation is a specification that, after
extensive consensus-building, has received the endorsement of the W3C and its Members. W3C recommends the wide deployment of this specification as
a standard for the Web. Future updates to this Recommendation may incorporate new features.
An Audiobook is a collection of audio resources grouped together by a reading order, metadata, and
resources, all contained in a manifest. This Audiobook can live on the Open Web Platform, or as a
packaged entity.
This specification is intended to standardize the audiobooks distribution model on the web and between
businesses. It should facilitate different user agent architectures for the consumption of Audiobooks.
The primary goal is to bring clarity to a part of the publishing industry currently underserved by
standards, while opening Audiobooks to the Open Web Platform and new user agents. This specification
does not outline what file types or formats should be used by content creators, only a manifest format
for delivering them.
This specification does not define how user agents are expected to render Audiobooks. Details about the
types of affordances that user agents can provide to enhance the reading experience for users are
instead defined in [pwp-ucr].
2. Terminology
Terms with meanings specific to the publishing industry are capitalized in this document (e.g., "Reading
System"). A complete list of these terms and
definitions is provided in [pub-manifest].
Only the first instance of a term in a section is linked to its definition.
In addition, the following terminology is defined for use in this specification:
Supplemental Content
Supplemental content is any content relating to the audiobook content but not required for the
full experience of the publication. Examples of supplemental content include photographs,
charts, or data relating to topics mentioned in the audiobook.
3. Conformance
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in
this specification are non-normative. Everything else in this specification is normative.
The key words MAY, MUST, MUST
NOT, RECOMMENDED, REQUIRED, and SHOULD in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and
only when, they appear in all capitals, as shown here.
4. Construction
4.1 Primary Entry Page
The primary entry page is an HTML resource that represents the preferred starting resource of an
Audiobook and enables discovery of its manifest. It typically introduces the audiobook and provides
access to the content.
An Audiobook MUST include a primary entry page except when packaging allows alternative
discovery of the manifest. When present, the page MUST be included in the
resource list.
4.2 Table of Contents
The table of contents provides a hierarchical list of links that reflects the structural outline of
the major sections of the Audiobook and any supplemental content it may contain.
The table of contents is expressed via an [html] element (typically a nav element) in
one of the resources. This element MUST be identified by the role attribute
[html] value "doc-toc" [dpub-aria-1.0].
If the table of contents is located in the primary entry page, the table of
contents MUST be the first element in the document — in document tree order
[dom] — with that role value. Otherwise, the manifest SHOULD identify the resource that contains the structure.
If the table of contents is not located in the primary entry page, the
manifest SHOULD identify the resource that contains the structure.
When an Audiobook contains additional resources (i.e. supplemental content):
a table of contents SHOULD be included;
the table of contents SHOULD include a link to any of the resources; and
When including supplemental content, be aware that users might not have access to this
content unless it is linked to from the table of contents. It is strongly advised to provide
links to all content that is not in the default reading order.
The Audiobook manifest is defined by a set of properties that describe the basic information a user
agent requires to process and render an Audiobook. These properties are categorized in the
Publication Manifest [pub-manifest]. Where these properties are extended
from the Publication Manifest is specified in this section.
Note
The Audiobook manifest is defined as a specific "shape" of [json-ld11].
This shape is also defined, informally, through a JSON schema [json-schema] that
expresses the constraints defined in this specification. This schema is maintained at https://www.w3.org/ns/pub-schema/audiobooks/.
5.2 Requirements
The requirements for the expression of Audiobook properties and resource relations are defined as
follows:
Note
The list of properties uses the formal names for each property as described in [schema.org] and [pub-manifest]. A
descriptive label is included in parentheses where the purpose of these properties might be
unclear.
Some properties are implicitly required, as they are compiled from alternative
information when not explicitly authored. Refer to the internal
representation data models [pub-manifest] for more
information (the Audiobooks representation only differs in the default value for the
type term).
5.3 Manifest Contexts
An Audiobook manifest has to start by setting the JSON-LD context [json-ld]. The
context has the following two major components:
If a type is not specified, Audiobook [schema.org] is assumed as the
default.
5.6 Properties
5.6.1 Creators
A creator is an individual or entity responsible for the creation of
the Audiobook. The Audiobooks profile can use the full list of creators defined in [pub-manifest].
The creators list includes two recommended creators for Audiobooks:
A duration is the length of the audio resources in an Audiobook. The
duration property is fully defined in Publication Manifest [pub-manifest].
Duration SHOULD be expressed for the entirety of the audiobook as part
of the manifest, and SHOULD be present at the item level in the default reading order.
When a content creator specifies both the duration for the audiobook and item-level duration in
the default reading order the resource-level duration SHOULD be equal to the sum of the durations of the items in the reading
order.
The default reading order MUST contain at least one audio resource, which
MAY be identified by the type of LinkedResource
[pub-manifest]. The default reading order MUST NOT contain non-audio resources.
An audio resource can be referenced in its entirety via a URL [url], or for content
where multiple chapters occupy a single file by using media fragments [media-frags] to locate the exact starting
and end points.
Note
It is important to note that a resource cannot be referenced more than once in the
reading order. In the case where an audio file represents the content of multiple chapters or
sections of the book, the table of contents can be used to specify the
starting and ending points of those chapters in the larger audio file, as demonstrated in this example.
Note
Annotations can also use media fragments to identify the location of the annotation in
the resource, and are compatible with the Web
Annotations model. This method will only apply to audiobook manifests that are not
packaged.
Example 8: Audiobook Reading Order for a Single Resource
The resource list enumerates any additional resources used in the
processing and rendering of an audiobook that are not listed in the reading order. It is expressed
using the resources property.
If an audiobook includes supplemental content it MUST be referenced in the
resource list.
The history of the audiobook is rooted in the world of accessibility. Both purely audio publications
and publications that synchronize text and audio playback have long been used to assist users with
alternative reading needs and preferences.
An approach for accessible synchronized media in publications is currently being done by the Synchronized Multimedia for Publications
Community Group. Refer to the work of that group for more information about creating such
content and incorporating it into an Audiobook.
Alternatively, a content creator can provide the text equivalent as HTML [html] resources in
the resources.
otherwise, if resource["duration"], add
resource["duration"] to resourceDuration.
If the values cannot be compared because data["duration"] is not set,
validation error.
Otherwise, if resourceDuration does not specify the same total
duration as data["duration"], validation
error.
Explanation
This step checks both that all resources in the reading order specify a duration and
that the sum of all those durations matches the total duration for the
publication.
A validation error is only emitted while checking each resource if the resource does
not specify a duration. The validity of the
durations [pub-manifest] is already checked in the publication manifest
algorithm so does not need to be repeated.
Data Validation
The following extension
steps are added for Audiobook manifests:
This step checks the reading order and resource list to verify that a cover has been
specified (i.e., an resource has the value cover in its
rel property).
7. User
Agent Processing of Machine-Processable Table of Contents
This section is non-normative.
This specification extends the Publication Manifest’s User Agent Processing Algorithm for
Machine-Processable Table of Contents [pub-manifest] to locate a table
of content element as follows:
If the primary entry page is available, then execute the
algorithm locating the table of content element on the primary entry page.
If the previous step is not successful, locate the relevant resource, if available, in the manifest
as described in § 4.8.1.3 Table of
Contents in [pub-manifest], and execute the same algorithm on
that resource.
As Audiobooks is a profile of Publication Manifest [pub-manifest], all security and privacy considerations
detailed in that specification are applicable to this profile.
This profile acknowledges the following considerations:
References within the Reading Order and Resource List can be references to both remote and local
resources.
9. User Agent Behaviors for
Audiobooks
This section is non-normative.
This section outlines the expected user agent behaviors for implementation of audiobooks. For processing
instructions, user agents should refer to the Processing a
Manifest section of the Publication Manifest [pub-manifest] specification, and conform to any behavior described there.
All user agent behaviors described in this section are intended to provide implementors with guidance,
not strict requirements. Behaviors in this document are taken mainly from the Use Cases and Requirements [pwp-ucr] note published by the working group.
9.1 Opening
and Navigating the Contents of an Audiobook
When a user agent opens an Audiobook, and the manifest processes according to the rules laid out in
Publication Manifest
[pub-manifest], it should be opened by the User
Agent. The Reading Order or, if available, Table of Contents should be accessible to the user. A User Agent should be able to provide
a list of the contents of the audiobook available to the user when requested. If a non-audio
resource is present in the Reading Order, the User Agent can choose to present it to the user or
skip it.
User agents should provide a means of rendering non-audio resources within the Reading Order and
Resource list. If the content cannot be rendered by the user agent, it is recommended that the user
agent inform the user that the content is present but cannot be rendered.
The Primary Entry Page is intended to be, when available, the entry point to
the audiobook. If a content creator has provided a primary entry page, and the User Agent is capable
of rendering or processing HTML content, it should be the first thing presented to the user. The
Primary Entry Page may or may not contain a Table of Contents, if included using the
role="doc-toc" it should be treated as the Table of Contents. If the Table of
Contents is a separate document, it can be rendered however the User Agent chooses as long as it
meets the requirements laid out above. If no Table of Contents is included in the Primary Entry Page
or elsewhere, the User Agent should refer to the Reading Order.
9.2 Audiobook Playability
As outlined in the Use Cases and Requirements [pwp-ucr] note, an audiobook
must be navigable in the User Agent. This means that a User Agent must provide methods for the user
to move through the audiobook in a linear or non-linear fashion by either moving through the Reading Order seamlessly or by accessing the Table of Contents. The User Agent should also allow the user to move through individual
audio files in short time increments.
For an audiobook, the User Agent should provide a player interface [pwp-ucr] that will allow the
user to navigate, play, or pause the audiobook. This interface can be represented to the user in any
way (i.e. physical buttons, visual interface, keyboard input, or voice commands), but should be
accessible at any point in the listening experience.
9.3 Audiobook Packaging and
Offlining
The Use Cases and Requirements [pwp-ucr] note recommends that
content be available offline and that any packaged formats should not affect the iterations of the
publications. This means that even if the content is copied many times to many users via multiple
User Agents, the core manifest and its identifier are never changed.
This specification recommends the Lightweight Packaging
Format [lpf] for packaging audiobook content,
but this is not a requirement. Audiobook User Agents should be able to ingest LPF files for play,
and should display content according to the requirements and recommendations in this document.
If a User Agent is serving the content directly from their service (i.e. as a retailer or repository
of content), it is recommended that they provide a method for offlining or downloading the content
to the user. This can be in any format they choose, but the audiobook should be complete and valid
and the contents listed in the manifest should be served in their entirety. Even if a User Agent
does not support the display of a certain resource (i.e. an image file or data table), it should
still be available to the user for download.
This specification does not provide a method for content creators to protect or watermark their
content, as there are existing methods available in the market today. User Agents who work with
content creators that wish to protect or limit the distribution of their content can choose a method
that works best for their requirements.
9.4 Audiobooks Accessibility
This specification recommends and provides a method for content creators to create fully accessible audiobooks. User Agents should use this information,
in the section on Accessibility, to implement accessible audiobook interfaces. It is recommended
that User Agents provide accessible player interfaces, as well as a method for content creators who
have provided alternate content to have that content displayed.
14-Sept-2020: Added a note that informative information about the table of contents structure and
formatting information is available in the Publication Manifest specification. See issue 97.
12-Sept-2020: Removed the manifest processing step that warns if a table of contents is not found as
the requirement is dependent on the presence of supplementary resources which cannot be reliably
tested. See issue 93.
8-Sept-2020: Clarified that the primary entry page is only required when the packaging does not
provide an alternative method. See issue
61.
26-Aug-2020: Removed the example of synchronized narration and updated reference to the work of the
Synchronized Multimedia for Publications Community Group to reflect the early nature of that work.
See issue 87.
2-July-2020: Added a note about the shape of the manifest being defined by the JSON schema to the
manifest introduction. See issue 71.
12-Feb-2020: The algorithm step to check and compare resource durations to the total audiobook
duration was moved to avoid duplicate validity checks. The algorithm step to warn about the primary
entry page not being listed in the unique resources has been removed as it is no checked in the
publication manifest algorithm. See issue
71.
12-Feb-2020: The use of fragments in the reading order was clarified to also include end position. A
number of examples were also fixed. See pull
request 69.
07-Feb-2020: The manifest requirements section was moved out of the properties section as it also
includes resource relations. See issue
70.
<head>
…
<scripttype="application/ld+json">
{
"@context" : ["https://schema.org","https://www.w3.org/ns/pub-context"],
"conformsTo" : "https://www.w3.org/TR/audiobooks/",
…
"url" : "https://publisher.example.org/janeeyre",
…
}
</script>
…
</head><body>
…
<sectionrole="doc-toc"><ol><li><ahref="audio/chapter001.wav">Chapter 1. There was no possibility of taking a walk that day...</a></li><li><ahref="audio/chapter002.wav">Chapter 2. I resisted all the way:...</a></li><li><ahref="audio/chapter003.wav">Chapter 3. The next thing I remember is,...</a></li>
…
</ol></section>
…
</body>
<navrole="doc-toc"><h2>JANE EYRE</h2><ol><li><ahref="audio/chapter001.mp3">Chapter 1. There was no possibility of taking a walk that day...</a></li><li><ahref="audio/chapter002.mp3">Chapter 2. I resisted all the way:...</a></li><li><ahref="audio/chapter003.mp3">Chapter 3. The next thing I remember is,...</a></li>
…
</ol></nav>
B.3 Table of Contents with
Media Fragments
A table of contents using media fragment references to locations in a single audio track.
The editor would like to thank the members of the Publishing Working Group for their contributions to
this specification:
Greg Albers (J. Paul Getty Trust)
Franco Alvarado (Macmillan Learning)
Boris Anthony (The Rebus Foundation)
Luc Audrain (Hachette Livre)
Baldur Bjarnason (The Rebus Foundation)
Laura Brady (W3C Invited Expert)
Steve Breault (Scenarex Inc.)
Don Brutzman (Web3D Consortium)
Kaylin Bugbee (Earth Science Data Systems Program)
Yu-Wei Chang (Taiwan Digital Publishing Forum)
Fred Chasen (W3C Invited Expert)
Timothy Cole (University of Illinois at Urbana-Champaign)
Simon Collinson (Rakuten, Inc.)
Rachel Comerford (Macmillan Learning)
Garth Conboy (Google, Inc., chair)
Juan Corona (Evident Point Software)
Christopher Cosner (Stanford University)
Dave Cramer (Hachette Livre)
Greg Davis (Pearson plc)
Romain Deltour (DAISY Consortium)
Marisa DeMeglio (DAISY Consortium)
Vagner Diniz (NIC.br - Brazilian Network Information Center)
Kenneth Dougherty (Pearson plc)
Brady Duga (Google, Inc.)
Ben Dugas (Rakuten, Inc.)
Roger Espinosa (University of Michigan)
Reinaldo Ferraz (NIC.br - Brazilian Network Information Center)
Teenya Franklin (Pearson plc)
Jun Gamo (Voyager Japan, Inc.)
Matt Garrish (DAISY Consortium)
Michael Goodman (Wiley)
Markku Hakkinen (Educational Testing Service)
Katie Haritos-Shea (Knowbility)
Ivan Herman (W3C Staff)
Geoff Jukes (Blackstone Audio, Inc.)
Deborah Kaplan (W3C Invited Expert)
Bill Kasdorf (Book Industry Study Group)
George Kerscher (DAISY Consortium)
Yuri Khramov (Evident Point Software)
Masakazu Kitahara (Voyager Japan, Inc.)
Toshiaki Koike (Voyager Japan, Inc.)
Charles LaPierre (Benetech)
Mustapha Lazrek (Microsoft Corporation)
Laurent Le Meur (EDRLab)
Vladimir Levantovsky (Monotype)
Mia Lipner (Pearson plc)
Phil Madans (Hachette Livre)
Christopher Maden (University of Illinois at Urbana-Champaign)
Dmitry Markushevich (Evident Point Software)
Keith McFarland (Blackstone Audio, Inc.)
Jonathan McGlone (University of Michigan)
Hugh McGuire (The Rebus Foundation)
Nellie McKesson (W3C Invited Expert)
Selma Morais (NIC.br - Brazilian Network Information Center)
Jasmine Mulliken (Stanford University)
Cristina Mussinelli (Fondazione LIA)
Christos Nikolakakos (Wiley)
Gregorio Pellegrino (Fondazione LIA)
Fernando Pinto da Silva (EDRLab)
Nicholas Polys (Web3D Consortium)
Chris Powell (University of Michigan)
Jeff Printy (Macmillan Learning)
Ryan Pugatch (Hachette Livre)
Joshua Pyle (Wiley)
Florian Rivoal (W3C Invited Expert)
Leonard Rosenthol (Adobe)
Robert Sanderson (J. Paul Getty Trust)
Jodi Schneider (University of Illinois at Urbana-Champaign)
Ben Schroeter (Pearson plc)
Tzviya Siegman (Wiley, chair)
Avneesh Singh (DAISY Consortium)
Adam Sisco (Earth Science Data Systems Program)
David Stroup (Pearson plc)
Mateus Teixeira (W. W. Norton & Company)
Jonathan Thurston (Pearson plc)
Yukio Tomikura (Kodansha, Publishers, Ltd.)
Ben Walters (Microsoft Corporation)
Daniel Weck (EDRLab, DAISY Consortium)
John Weise (University of Michigan)
Jason White (Educational Testing Service)
Richard Wright (EDRLab)
Jeff Xu (Rakuten, Inc.)
Evan Yamanishi (W. W. Norton & Company)
Maurice York (University of Michigan)
Junichi Yoshii (Kodansha, Publishers, Ltd.)
Benjamin Young (Wiley)
Mohamed ZERGAOUI (INNOVIMAX)
The Working Group would also like to thank the members of the Digital Publishing Interest Group for all the hard work they did paving the road for this
specification.