Searching for Common Ground with Fixed-Layout eBooks

Digital Issues Working Group (DIWG) of the Association of American Publishers, Inc. • October 23, 2011

Fixed-layout eBooks are important to publishers as we digitize children’s books and other highly-designed titles. Apple and Barnes & Noble have developed early implementations of this concept, and we hope Amazon will soon release details of their new format. Consistent approaches to certain technical issues will greatly facilitate development of the market.

General Principles

Any proposed fixed-layout format should meet the following criteria:

Publishers should be able to create a single file that can be used and interpreted consistently by all retailers.
The format should gracefully adapt to current and future devices and screen sizes, preferably without complex media queries or multiple packages.
The format should be valid EPUB 3.X.
The format and all internal components should be easily edited and corrected.
File size should be kept to a minimum without compromising function or media quality.
The format should allow for interactivity and multimedia using CSS, JavaScript, and SMIL.
The format should allow for robust and straightforward QA and testing
The format should allow for accessibility.

We believe that EPUB 3.0 as approved by the IDPF, can meet these requirements.

What’s Out There?

	Content	Styling	CSS Units	Granularity	Metadata	Notes
Amazon Kindle Format 8	HTML	CSS	?	?	?
Apple iBooks Fixed Format	HTML	CSS	px	page	HTML meta tag	supports SMIL, JavaScript
Barnes & Noble Fixed Format	Image with text overlay	CSS	px, em, %	unknown	custom XML file	Layered text and images
Sony Fixed Format	HTML	CSS?	unknown	unknown	in OPF
Image in HTML	Image	CSS (minimal?)	?	any	?
SVG in Spine	SVG	—	—	page or spread	?	Hard to edit, potential file size and performance issues
JPEG in Spine	JPEG	—	—	page or spread		Not allowed by EPUB 3.0 without fallback
PDF	PDF	PDF	n/a	any		Not EPUB; web-based approaches to multimedia and interactivity won’t work

We are aware of other implementations, but details have not been made public.

AAP DIWG Proposal

We propose a two-tiered approach, with a simple, image-based EPUB for content that may never need interactivity, and a full HTML + CSS approach for everything else.

Simple Fixed Layout

Content: JPEG , SVG, or other image format, wrapped in either SVG or HTML as needed.

Granularity: One image per page

General Fixed Layout

Content: HTML + CSS absolute positioning + images + JavaScript? + SMIL?

CSS Units: Percentage (but there could be issues with subpixels; further discussion is probably warranted)

Audio: MP3

Video: MP4

Fonts: OpenType

Granularity: One HTML file per page or spread

Format-specific metadata: Generic metadata should be expressed once, using a common vocabulary. If individual retailers require additional unique metadata, it should be stored in an individual file in META-INF.

Comment by amitv.vo...@gmail.com, Jan 11, 2012

With standard reflowable ePub atleast you were assured of standardization, however all major retailers have taken the opportunity to invent their own Fixed Layout Formats...I believe standardization is important both from publishers and users standpoint.

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