Enhanced Ebook Guidelines

What is an enhanced e-book?

This term is used to describe e-books that include multimedia content, such as audio and video, or other interactive components. These books go beyond linked end notes and embedded fonts to create a more rounded reading experience; however, they do come with a few limitations. Some enhancements are not compatible with every e-book file type, and not every retailer or e-reader device supports these books. Every major retailer (iBooks, Google Play, Kindle, Kobo, and Nook) has some level of support for multimedia enhancements, although each has its own specifications for formatting and file sizes. For more info and technical specs for multimedia enhancements, see the chart at the bottom of this page.

Your editor will determine whether an enhanced e-book feature is appropriate for your project. Discuss this with your editor as early in the process as possible if this is of interest.

What enhancements can be made to an e-book?

Current technology allows for several kinds of media additions. The most basic are audio and video files, but more complicated additions such as narration are also possible. These additions are often added alongside or immediately after relevant passages in order to enhance rather than distract from the content of the text.

Audio

E-book enhancements allow audio files to be used in several ways. Audio files can be added in conjunction with relevant passages in the text and will appear in the book as icons with a play button that the reader can select when ready. Narration can also be added, allowing readers to follow along, and current words or sentences can be highlighted, although this feature is usually seen only in children’s books. Finally, the least common of the audio additions is background music, but this feature is rare and is supported only through Apple’s iBookstore.

Video

This is the most common addition to enhanced e-books but also one of the most restrictive. Full-length videos can be embedded in the file without need for an internet connection, but many e-book retailers have file size limits that can limit length or quality. Like audio files, videos are best included after relevant passages in the text. With these restrictions in mind, IU Press recommends that you use only short relevant videos as a supplement to the text rather than as a substitution for it. Each video should also include a poster image, or thumbnail, to display before the video is played, and at least one black frame at the beginning and end.

Animation

Another enhancement is simple animation. These animations are created in layers with CSS (Cascading Style Sheets) and are only two-dimensional. Animations are most commonly used in children’s books but are technically possible in other applications. This webpage has more information, as well as an example of what an e-book animation can look like: http://ebookarchitects.com/learn-about-ebooks/enhanced-ebooks/

  Amazon iBookstore Kobo Nook Google Play
Max file size 650 MB 2 GB, 200 MB recommended 100 MB 20 MB 2 GB
Video Supported on apps, not on Kindle Fire        
Video contd. H.264 H.264 H.264
Video contd. MPEG-2 MPEG-4
Video contd. MP4 .mv4 or .mp4 .3gp / .3g2 / .mp4
Video dimensions Wide screen: 704x396 full screen: 640x480 640x480 or 640x 360 (SD), 1920x1080 (HD) 176x144 up to 854x480
Interlacing Progressive Progressive
Color space 4:2:0 YUV ITU-R BT.709 (HD)
Video mode VBR or CBR VBR
Video bit rate 2500 kbps 40-60 mbps (SD) 220 mbps (HD)
Key frame interval 2 or 4 seconds
In-video audio          
Encode MP3 AAC AAC LC / LTP or AAC HeV1 / HeV2
Mono/stereo Stereo
Bit rate 256 kbps or higher 256 kbps Up to 320 kbps
Sample rate 48 kHz recommended All files must have same sample rate
Additional video specs Must include caption, video time, poster image and black end frame. Poster image 150 px by 300 px. End with one black frame.
Audio          
Extension .mp3 .m4a Mp4, mp3, ogg, AAC
Encoding MP3 AAC/MP4 MP4 ACC compressed only
Mono/stereo Stereo Stereo Mono/stereo
Bit rate 128 to 256 kbps 256 kbps Max 320 kbps

More information on enhanced e-books

These pages have more information on technical specs for enhancements as well as general information on these types of publications:

https://ebookarchitects.com/concourse/specifications.php
https://kindlegen.s3.amazonaws.com/AmazonKindlePublishingGuidelines.pdf
https://itunesconnect.apple.com/docs/iBooksAssetGuide5.1Revision2.pdf
http://ebookarchitects.com/learn-about-ebooks/enhanced-ebooks/
http://help.180g.co/vellum/file-size/