The one disappointment I had was that this widget does not support voiceover narration. This can seriously diminish the value of a slide presentation. The reader can flip through the slides forward and backward but they have to guess what the presenter might have said. Peter Norvig did a wonderful six slide Powerpoint presentation illustrating this very point. See the slides for President Lincoln's Gettysburg Address here. View the slides on-line or download the presentation as a *.ppt file.
As you'll see, there is something missing, something very important.
Of course there is a way around this. In Keynote, you can add a voiceover and export the presentation as a video to include in your iBooks Author project using the media widget. You can also use screen casting software such as ScreenFlow to capture slides, narration and even a secondary video source such as a PIP (picture-in-picture) of the speaker. The problem with these audio-annotated slideshows done as video is that their file sizes are unnecessarily large. This is a problem for iBooks both because of the 2 GB limit and the time it takes for readers to download very large iBooks. This might well reduce ones audience.
My use of the word "unnecessarily" should signal that there might be an even better workaround and there is – sort of. What I'm about to describe would be a great workaround if it were supported by iBooks Author. It is not currently supported in iBooks Author but users of that application can change that. Request an enhancement right from within iBooks Author like this:
The workaround that's better than a video is called an "enhanced audio" file. It is created in GarageBand and carries the *.m4a file name suffix.. You may also see it referred to as an "enhanced podcast" file. What makes the enhanced audio file such a great alternative to video is that it uses one static image of a slide over its entire time on screen instead of 30 frames per second as in a video. If a 50k slide is on-screen for 100 seconds in an enhanced audio file, that image contributes only 50k to the total file size. If a 50k slide is on screen for 100 seconds in a video file, that image contributes 150,000k ([50*30]*100) to the total file size. That's 50k vs 150 Mb, a 3000:1 ratio in this example! In real life, the difference is somewhat less than this because good video encoding uses a number of neuroscience-based tricks to present incomplete data in between the key frames that are full representations of what the camera captured. That fools the eye and takes less space. Still, the difference is quite significant. We'll look at a real world comparison below.
Since this is not a how-to post, I'll leave that task to others. There are many fine tutorials teaching you how to use GarageBand to create enhanced audio files on the web. Here's a good one in the form of a PDF.
I created an example using some ancient media describing the beginnings of the Space Shuttle program. Intended for school use, the package contained a cassette audio tape and a set of photo slides. The audio tape has sharp "beeps" to tell the projector operator when to advance to the next slide image. I've left those beeps in for their nostalgia value. Here's the enhanced audio file slide show:
You may download a copy of this file here and it will play (larger) in QuickTime X Player, in the iTunes.app and may other venues that support QuickTime but just not iBooks Author and the iBooks it creates. This 18 minute presentation is only 21.4 MB in size! Space-efficiency isn't the only advantage of enhanced audio files. The assembly of the static images creates a chapter track that enables the viewer to quickly and easily move to any part of the presentation. This is great for studying a topic where revisiting a difficult section is helpful. Here's a screenshot to illustrate what a chapter track looks like:
Here's a view of the GarageBand project that created this enhanced audio file:
So, what would this presentation cost us in terms of file size if it were a video? I created an *.mp4 version with ScreenFlow using the same assets. That version weighed in at 198.2 MB. You may download a copy of that file here. The *.m4a file tipped the scales at 21.4 MB. The video version is approximately 9.3 times larger than the enhanced audio file yet playing them side by side reveals no important differences. Here's a screencast of that analysis:
If you'd like to download and view a larger version of this video, you may do that here.
The one on the left is the c. 200 Mb video and the one on the right is the c. 20 Mb enhanced audio file. So, if you are at all impressed by the potential advantages of being able to use an enhanced audio file in an iBooks Author project, send in that enhancement request to Apple as described above and do that ASAP.
By the way, you can add an enhanced audio file to an iBooks Author project and it will play the audio part. No slides though and that's where the biggest advantage is. Here's what that looks like in iBooks Author.
Note that there is an option for "Show Audio As:" that includes an "Image" option. That doesn't make the slides appear though. That's for drag/dropping a single image onto it that will appear throughout the duration of the audio. Yes, I got real excited when I first saw that.