In 2011, I worked on a project to create a print-on-demand book called Playing Erhu – Bridging the Gap. Besides the typical embedded vector graphics, this music instruction book used a Microsoft Word macro and custom font to render numbered musical notation. The result of the project is a 128 page, letter sized PDF file ready for on-demand printing. In addition, there are over 200 companion MP3 files hosted on a web server. The book has been shipped to over 30 countries.
Not surprisingly, customers inquired about an electronic option, to which the answer was no, since we did not have a way yet to protect the intellectual property, which was simply a PDF file.
Meanwhile, e-readers such as Kobo and Amazon Kindle were gaining popularity. These readers use EPUB which are great for novels, but less satisfactory for books with special graphics and multi-media content. In the Apple camp, their iBooks Author uses a proprietary EPUB like format.
Since all the formatting already exists in the PDF file, it would save a lot of effort if the PDF file could be used as is. By wrapping the PDF file within an app, it could be sold through an app store. Although mobile apps can launch external viewers to show content, the app loses control and feedback as to where the user has navigated. The app needs some kind of programmatic viewer which was found in RadaeePDF SDK. With this SDK, as the user navigates to a page, the app can play back the audio corresponding to that page. At the time of development, the file size limit of an app on Google Play was 50 MB, which was enough to include about 50 of the 200+ MP3 files. On first use, the app downloads the remaining MP3 files to the mobile device’s local storage.
What about iOS? Although the RadaeePDF SDK is available for iOS, I am not confident that Apple, with their strict approvals, would allow a “book” wrapped in an app in the App Store. Rather than risk spending the time and money on developing an iOS version and being rejected by Apple, the app is Android-only. It sells for $29 USD on Google Play, and I am happy to report that it has sold enough units to re-coup the $700 USD licensing cost of the RadaeePDF SDK.