This specification describes the requirements for the creation of audiobooks, using a profile of the Publication Manifest specification.

This draft is still under consideration within the Publishing Working Group and is subject to change. The most prominent issues will be referenced in the document with links provided.

Introduction

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]].

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.

Construction

Primary Entry Page

The primary entry page represents the preferred starting resource for an Audiobook and enables discovery of its manifest.

The primary entry page is an HTML resource that typically introduces the audiobook and provides access to the content. It SHOULD contain the table of contents.

It is not required that the primary entry page be included in the default reading order, as the Audiobooks profile requires that only audio resources be present. The primary entry page should instead, if present, be included as a resource.

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):

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.

Manifest

Introduction

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.

Manifest Contexts

An Audiobook manifest has to start by setting the JSON-LD context [[!json-ld]]. The context has the following two major components:

		{
			"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
			…
		}
				

To add the global language and direction of the manifest metadata, language and direction declaration [[!pub-manifest]] can also be added to the context:

						{
							"@context" : [
								"https://schema.org",
								"https://www.w3.org/ns/pub-context",
								{"language":"fr"}
							]
							...
						}
				

Publication Conformance

The conformance URL expressed in the conformsTo term [[!pub-manifest]] MUST be "https://www.w3.org/TR/audiobooks".

						{
								"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
								"conformsTo" : "https://www.w3/org/TR/audiobooks/"
								…
						}
				

Publication Type

The Publication Type is defined using the type term [[!pub-manifest]].

{
    "@context" : ["https://schema.org", "https://www.w3.org/ns/wp-context"],
    "type"     : "Audiobook"
    …
}

If a type is not specified, Audiobook [[!schema.org]] is assumed as the default.

Properties

Requirements

The requirements for the expression of Audiobook properties are defined as follows:

REQUIRED:
RECOMMENDED:

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).

Creators

A creator is an individual or entity responsible for the creation of the Web Publication. The Audiobooks profile can use the full list of creators specified in Web Publications.

The creators list includes two recommended creators for Audiobooks:

		{
		    "conformsTo" : "https://www.w3/org/TR/audiobooks/",
		    "@context" : ["https://schema.org","https://www.w3.org/ns/pub-context"],
				"type" : "Audiobook",
		    …
		    "url" : "https://publisher.example.org/janeeyre",
		    "author" : {
		        "type" : "Person",
		        "name" : "Charlotte Bronte"
		    }
		}
					
		{
				"conformsTo" : "https://www.w3/org/TR/audiobooks/";
				"@context": ["https://schema.org", "https://www.w3.org/ns/pub-context"],
				…
				"url"	: "https://publisher.example.org/janeeyre",
				"author" : {
						"type": "Person",
						"name": "Charlotte Bronte"
				}
				"readBy" : {
						"type": "Person",
						"name": "Ivan Herman",
						"id"	: "https://www.w3.org/People/Ivan/"
				}
		}
					

Duration

A duration is the length of the audio resources in an Audiobook. The duration property is fully defined in the Publication Manifest specification.

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.

									{
											"conformsTo" : "https://www.w3/org/TR/audiobooks/",
											"@context" : ["https://schema.org","https://www.w3.org/ns/pub-context"],
											…
											"url" : "https://publisher.example.org/janeeyre",
											"author" : {
													"type"  : "Person",
													"name"  : "Charlotte Bronte"
											},
											"duration" : "PT12345.235S"
									}
					

Default Reading Order

The default reading order is a specific progression through the audio resources in the audiobook.

The default reading order MUST contain at least one audio resource, which MAY be identified by the type of LinkedResource. 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 point.

							{
								"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
								"conformsTo" : "https://www.w3/org/TR/audiobooks/",
								"url" : "https://publisher.example.org/janeeyre",
								"name" : "Jane Eyre",
								"readingOrder" : [{
									"type" : "LinkedResource",
									"url" : "audio/janeeyre.mp3",
									"encodingFormat" : "audio/mp3",
									"name" : "Jane Eyre",
									"duration" : "PT124503.123S"
								}]
							}
					
							{
								"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
								"conformsTo" : "https://www.w3/org/TR/audiobooks/",
								"url" : "https://publisher.example.org/janeeyre",
								"name" : "Jane Eyre",
								"readingOrder" : [{
									"type": "LinkedResource",
									"url" : "audio/part001.wav#0",
									"encodingFormat" : "audio/vnd-wav",
									"name" : "Chapter 1",
									"duration" : "PT457.931S"
								}, {
									"type" : "LinkedResource",
									"url" : "audio/part001.wav#457.932",
									"encodingFormat" : "audio/vnd-wav",
									"name" : "Chapter 2",
									"duration" : "PT234.245S"
								}]
							}
						

Resource List

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.

						{
							"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
							"conformsTo" : "https://www.w3/org/TR/audiobooks/",
							"url" : "https://publisher.example.org/janeeyre",
							"name" : "Jane Eyre",
							"resources" : [
								"cover.jpg",
								"portrait_CB.jpg",
								"supplement.pdf"
							]
						}

Audiobook Previews

Previews are a common way to provide users an experience of the full content before purchasing or downloading the full audiobook.

A preview is identified using the preview link relation, as defined in [[pub-manifest]].

Previews MAY be located externally or included as a resource of the audiobook.

							{
								"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
								"conformsTo" : "https://www.w3/org/TR/audiobooks/",
								"url"	: "https://publisher.example.org/janeeyre",
								"name" : "Jane Eyre",
								"resources" : [{
									"type" : "LinkedResource",
									"url" : "https://publisher.example.org/jane-eyre-preview.wav",
									"encodingFormat" : "audio/wav",
									"rel" : "preview"
								}]
							}
							{
								"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
								"conformsTo" : "https://www.w3/org/TR/audiobooks/",
								"url"	: "https://publisher.example.org/janeeyre",
								"name" : "Jane Eyre",
								"resources" : [{
									"type" : "LinkedResource",
									"url"	: "preview.wav",
									"encodingFormat" : "audio/wav",
									"rel"	: "preview"
								}]
							}

Packaging

Audiobooks will be packaged using the method described in the Lightweight Packaging Format note.

Accessibility

The history of the audiobook is rooted in the world of accessibility. To create a fully accessible audiobook, it is recommended to use the Synchronized Media note to create documents where text and audio can be completely synchronized.

To create an accessible audiobook using Synchronized Media, you need to both reference the alternative file on the item in the reading order, as well as list the file in the resources.

Alternatively, a content creator can provide the text equivalent as HTML [[html]] resources in the resources.

At the time of this publication, a Synchronized Media specification suitable for use in audiobooks is in development. It is believed this specification can already meet synchronization needs, though reliance on a developing specification clearly carries no guarantee of backward compatibility. Participation and comments from the digital publishing community, and especially from implementors are encouraged.

				{
					"@context" : ["https://schema.org", "https://www.w3.org/ns/pub-context"],
					"conformsTo" : "https://www.w3/org/TR/audiobooks/",
					"url" : "https://publisher.example.org/janeeyre",
					"name" : "Jane Eyre",
					"readingOrder" : [{
						"type" : "LinkedResource",
						"url" : "audio/part001.wav",
						"encodingFormat" : "audio/vnd-wav",
						"name" : "Chapter 1",
						"duration" : "PT457.931S",
						"alternate" : {
							"type" : "LinkedResource",
							"url" : "sync-media/part001-1.json",
							"encodingFormat" : "application/vnd.wp-sync-media+json"}
					}, {
						"type" : "LinkedResource",
						"url" : "audio/part001.wav#t=457.932",
						"encodingFormat" : "audio/vnd-wav",
						"name" : "Chapter 2",
						"duration" : "PT234.245S",
						"alternate" : {
							"type" : "LinkedResource",
							"url" : "sync-media/part001-2.json",
							"encodingFormat" : "application/vnd.wp-sync-media+json"}
					}],
					"resources" : [{
			      "type": "LinkedResource",
			      "url": "sync-media/part001-1.json",
			      "encodingFormat" : "application/vnd.wp-sync-media+json"
			    }, {
						"type": "LinkedResource",
						"url" : "sync-media/part001-2.json",
						"encodingFormat" : "application/vnd.wp-sync-media+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",
					"name" : "Jane Eyre",
					"readingOrder" : {
						"type" : "LinkedResource",
						"url" : "audio/part001.wav#0",
						"encodingFormat" : "audio/vnd-wav",
						"name" : "Chapter 1",
						"duration" : "PT457.931S",
						"alternate" : {
							"type" : "LinkedResource"
							"url" : "text/part001-1.html",
							"encodingFormat" : "text/html"}
					},
					"resources" : [{
			      "type": "LinkedResource",
			      "url": "text/part001-1.html",
			      "encodingFormat" : "text/html"
			    }...
					]
				}
			

Manifest Processing

This section depends on the Infra Standard [[!infra]].

The specification extends the Publication Manifest processing algorithms [[!pub-manifest]] as follows:

Generating the Internal Representation

The following extension steps are added for Audiobook manifests:

  1. ( and ) If document is not defined or does not include an [[!html]] element with the role doc-toc:

    1. let toc be a boolean value set to false.

    2. for each resource of processed["resources"], if resource["rel"] is defined and contains the value contents, set toc to true, then break.

    3. if toc is not true, validation error.

Data Validation

The following extension steps are added for Audiobook manifests:

  1. () Check the reading order as follows:

    1. if data["readingOrder"] is not set or is an empty list, fatal error, return failure. Otherwise, if data["readingOrder"] does not contain at least one item with an audio media type, fatal error, return failure.

    2. otherwise, for each resource in data["readingOrder"], if resource is not an audio resource, validation error, remove resource from data["readingOrder"].

  2. () If data["type"] is not set or is an empty list, validation error, set to « "Audiobook" ».

  3. () Check that each of the following properties is set. If not, issue a validation error for each one.

    • data["abridged"]
    • data["accessMode"]
    • data["accessModeSufficient"]
    • data["accessibilityFeature"]
    • data["accessibilityHazard"]
    • data["accessibilitySummary"]
    • data["author"]
    • data["dateModified"]
    • data["datePublished"]
    • data["id"]
    • data["inLanguage"]
    • data["name"]
    • data["readBy"]
    • data["readingProgression"]
    • data["resources"]
    • data["url"]
  4. () If no resource in data["readingOrder"] or data["resources"] has a rel entry that contains the relation cover, validation error.

  5. () Check the duration of the publication as follows:

    1. Let resourceDuration hold the total duration of individual resources.

    2. For each resource of data["readingOrder"]:

      1. if resource["duration"] is not defined, validation error.

      2. otherwise, if resource["duration"] is not a valid duration value, per [[!iso8601]], validation error, remove resource["duration"].

      3. otherwise, add resource["duration"] to resourceDuration.

    3. If data["duration"] is not set, validation error. Otherwise, if resourceDuration does not specify the same total duration as data["duration"], validation error.

Security and Privacy Considerations

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:

User Agent Behaviours for Audiobooks

This section outlines the expected user agent behaviours for implementation of audiobooks. For processing instructions, user agents should refer to the Processing a Manifest section of the Publication Manifest specification, and conform to any behaviour described there.

All user agent behaviours described in this section are intended to provide implementors with guidance, not strict requirements. Behaviours in this document are taken mainly from the Use Cases and Requirements note published by the working group.

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, 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.

Audiobook Playability

As outlined in the Use Cases and Requirements 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 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.

Audiobook Packaging and Offlining

The Use Cases and Requirements 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 it's identifier are never changed.

This specification recommends the Lightweight Packaging Format 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.

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.

Manifest Examples

Simple Audiobook

A manifest for an audiobook. The canonical version of this manifest is also available.


			

Audiobook with Supplemental Content

A manifest for an audiobook with supplemental content.

					{
						"@context" : ["https://schema.org", "https://www.w3/org/ns/pub-context"],
						"conformsTo" : "https://www.w3/org/TR/audiobooks/",
						"id" : "https://publisher.example.com/janeeyre",
						"url" : "https://publisher.example.com/janeeyre",
						"name" : "Jane Eyre",
						"author" : "Charlotte Bronte",
						"readBy" : "Jane Doe",
						"duration" : "PT123456.789S",
						"abridged" : "false",
						"inLanguage" : "en",
						"dateModified" : "2019-03-29T15:59:00Z",
						"datePublished" : "2019-03-29",

						"readingOrder": [
							{"url": "audio/chapter001.aac", "encodingFormat": "audio/aac", "name": "Chapter 1", "duration": "PT1234.567S"},
							{"url": "audio/chapter002.aac", "encodingFormat": "audio/aac", "name": "Chapter 2", "duration": "PT890.123S"},
							{"url": "audio/chapter003.aac", "encodingFormat": "audio/aac", "name": "Chapter 3", "duration": "PT456.789S"},
							{"url": "audio/chapter004.aac", "encodingFormat": "audio/aac", "name": "Chapter 4", "duration": "PT987.654S"},
							{"url": "audio/chapter005.aac", "encodingFormat": "audio/aac", "name": "Chapter 5", "duration": "PT321.987S"}
						],

						"resources": [
						{"rel": "cover", "url": "images/cover.jpg", "encordingFormat": "image/jpeg"},
						{"rel": "contents", "url": "toc.html", "encodingFormat": "text/html"},
						{"url": "haworth_house.pdf", "encodingFormat": "application/pdf"}
						]
					}
				

Table of Contents Examples

Primary Entry Page with a Table of Contents

A primary entry page with a simple table of contents for an audiobook.

					<head>
				    …
				    <script type="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>
				    …
				    <section role="doc-toc">
							<ol>
							 <li><a href="audio/chapter001.wav">Chapter 1. There was no possibility of taking a walk that day...</a></li>
							 <li><a href="audio/chapter002.wav">Chapter 2. I resisted all the way:...</a></li>
							 <li><a href="audio/chapter003.wav">Chapter 3. The next thing I remember is,...</a></li>
							 …
							</ol>
				    </section>
				    …
				</body>
					

Simple Table of Contents

A table of contents for a simple audiobook.

					<nav role="doc-toc">
						 <h2>JANE EYRE</h2>

						 <ol>
							<li><a href="audio/chapter001.mp3">Chapter 1. There was no possibility of taking a walk that day...</a></li>
							<li><a href="audio/chapter002.mp3">Chapter 2. I resisted all the way:...</a></li>
							<li><a href="audio/chapter003.mp3">Chapter 3. The next thing I remember is,...</a></li>
							…
						 </ol>
						</nav>
				

Table of Contents with Media Fragments

A table of contents using media fragment references to locations in a single audio track.

					<nav role="doc-toc">
						<h2>JANE EYRE</h2>

						<ol>
							<li><a href="https://example.publisher.org/janeeyre/part001.mp3">Chapter 1</a></li>
							<li><a href="https://example.publisher.org/janeeyre/part001.mp3#t=456.789">Chapter 2</a></li>
							<li><a href="https://example.publisher.org/janeeyre/part001.mp3#t=1234.567">Chapter 3</a></li>
						</ol>
					</nav>