We have a Universal iOS app. We use JSON to download content into the app during the first launch.
The size of content being downloaded on iPad (due to large image sizes) is about 100MB and on iPhone (smaller images) 80MB.
It takes about 4-7 minutes to download all content over WiFi. On 3G it takes 7-10 minutes.
Images are large in size, text content is not so much.
Is there any way we could reduce the download time? I'm aware of JSON compression but not sure if it will help with images?
Any ideas?
Tx
Some of this information has been mentioned in various comments, but it's what I would have suggested anyway and I figured having an answer written up would be more useful, so here goes:
Instead of storing the location of each image in the JSON file and downloading them one at a time, store the images in zip files and download those. Any amount of compression you get from this is an improvement in your download time, and you can simply unzip the images once you've downloaded the zip files.
Store a reasonable amount of the images in the main bundle along with the app. In your case you clearly can't store them all there; you don't want to have a huge app, and since it's a recipe app I presume you'll be adding more recipes as you go along. It makes a lot more sense to be able to update and download recipes via the JSON than to have to push a new version of the app to the app store with each change. But there are some items that can be bundled with the app; ex. large background images, design elements that are constant and unlikely to change. Any image which won't be likely to need updating should be bundled with the main app; any savings on download time is an improvement.
Have some kind of interesting loading screen. This is very important since you're talking about 4-10 minute download times. That is a long time for a user. When engaging with an application, 30 seconds can even seem like a long time. You're going to be hard pressed to make me willing to sit there and wait for 10 minutes for the app to begin if nothing is happening during that time. Have creative vegetable characters move across the screen, include a little interactive puzzle or ingredients on the loading screen, something. Just give the user something to look at (or preferably something interactive to do) while they're waiting. Otherwise you're probably going to lose a lot of users during this download.
If you can make this work, it really is a good idea to only download items when necessary. For example if your recipe app is broken into "Salads", "Fish", "Chicken", "Desserts", etc., you could prompt the user to download the recipe information for each category the first time they click on it. The great thing about this is that it breaks up the time the user has to spend waiting on the download; let's say you have 10 recipe categories, now the time the user has to wait all at once has been decreased from 4-10 minutes to 30 seconds-1 minute. That is a huge difference. I'll wait 1 minute for the Dessert recipes (still give them something to do!) much more readily than I'll wait 10 minutes for the whole app.
4b. You mentioned not being able to access new content while offline, which is a valid concern. To address this you could have a prompt the first time the app loads: This application contains hundreds of exciting recipes and delicious images. It can take several minutes to download all this yummy information. You can download all the content now, or proceed to the app and download recipes by category when you wish to view them. Please note that this will require an internet connection. And the buttons could say something like Download Now and Proceed to App. Obviously you can play with the wording to your heart's content, but the idea is sound. You've informed the user that there might be a significant download time, so at least they're forewarned, and they can make their own decision about how to use your app.
However you decide to proceed, break up the content you download into logical categories for the zip files. For example, "Desserts.zip", "Salads.zip", etc. That way even if you don't decide to let the user download on-demand now, you've set up a structure that is open to change later on.