An important consideration for tablet apps is file size. One should always try and keep files sizes to a minimum, making it quicker and easier to download and store on the device. This is especially applicable to video and images.
Text is always rendered best when using the PDF format. When possible you should be using the PDF format for text rendering which gives you the best possible flexibility. PDF is an excellent page format for printing on paper due to its standardisation and its being a vector format. Vector formats contain instructions for the page rather than a picture of a page which is what bitmapped formats such as JPG and PNG are.
The best way to use PDF is as image type rather than a page type. And its best for images that contain a mix of text and imagery. PDF pages can not be reflowed for different screen sizes. However if your PDF is an image on a page, for example text flowing around curve thats in a photo then that image can be reflowed in the page using Oomph's Smartfit feature.
Large heavy PDF files such as bitmaps in ads or in a page layout will slow down the rendering speed of the page which is only natural as the iPad can only hold so many pages in memory (although the 2nd and 3rd generation iPads are a lot better than iPad 1). Always keep your files as slim as possible for the best rendering of the publication.
Another thing we have found that seems to effect the rendering speed is using drop shadow filters in InDesign. Once rendered in PDF and then dropped onto an iPad seems to slow the rendering of page when swiping. Try to cut down on extensive use of these in you pages if you are using them.
Things like Flipbooks are the only feature that require the use of JPGs or PNGs. Any other feature allows you to use either PDF or an image based format which can be used together so for instance a slide show can have a PDF slide and jpg/png slide together.
Consider options such as an In Page Video or Animated Image before using animated GIFs. Animated GIFs are inefficient, resource heavy and have a poor colour accuracy.
Wherever possible, size images exactly i.e. if your image is going to be displayed at 150px x 150px resize your image to those exact dimensions. Refrain from using hi res images in apps. 132 dpi is sufficient, as it will cater for the retina screen of the iPad 3. 72dpi is sufficient for iPad 1 and 2. For Full Page Slideshows place images straight into the S1 folder rather than exporting through InDesign first.
Video and Audio
Using video and audio is great and they add that much more to the publication experience but be considerate in your use of both of these tools. Don’t have video/audio blast from the device when a reader turns the page. Be respectful of the reader and where they may be. Again it’s about the user feeling in control and driving the experience rather than you controlling their experience. Always provide the use with the option of stopping the music or video by providing clear navigation.
For video formats it’s always best to use MP4 over MOV for better cross platform video. Use MP4 for video with the H264 codec. Encode for quality versus speed. Consider using ¼ screen size for video, the iPad will scale it up with little loss in quality. There are many options as to how you can use video with Oomph from In Page Video to Fullscreen Video or use it with a HTML overlay.
Quicktime is a great companion for editing, exporting, file formats on the mac if you are
looking for a cheap, reliable program.
Don’t put small size text in videos - instead, consider using an PDF layer on top. Quick tip: the PDF layer can be timed to appear at a certain time in the video.
Streaming video is an option you may want to consider over embedding video in your app. It will require the reader to have a wifi connection to view the video but will help to keep app size to a minimum. The AFL Record Publication use streaming video very successfully. An alternative to video is using the Oomph animation engine to create certain effects.
Oomph Animations render very smooth results as they are powered by the graphics chip in the tablet. Animations file sizes are vastly smaller than video. Animations can be applied to both page layers and objects/widgets. In addition to faster page loading, using animations in objects will also enable easier translation between different screen sizes.
Animations can also be a great way to provide hints to interactivity. Consider custom animations such as 'quickshimmy' or 'quickpulse' which are short lived, subtle animations. Cars Guide are a great example of this being used effectively, however it's important to not let animations affect the performance of the page.