Odd that this didn’t come to light earlier, but seems that there was a pretty significant bug introduced in iOS 6.0, which is fixed in iOS 6.0.1, that causes podcast episodes to download over and over again while you’re listening to the episode. Essentially, although you might have finished downloading the whole file in the first couple minutes, iOS would go back and re-download it all over again. And again. And again.
This only came to light recently after Public Radio Exchange Labs (PRX) looked at their server data after getting a much larger than expected bill from the CDN provider. The PRX blog post goes into all the technical details thoroughly, so venture there if you want the whole scoop, but for the skinny you just have to look at this graph:
Yeah that giant peak? That’s when iOS 6.0 came out. The drop? Yep, iOS 6.0.1. Why didn’t it drop back down to baseline? Because people haven’t updated to iOS 6.0.1. This could be a huge deal for you if you listen to podcasts with on a cell network and/or haven’t updated your carrier settings (which for many carriers iOS wasn’t switching to WiFi when it was available. You could rack up some serious data overage charges. How bad? PRX gave these examples:
In one case, the playback of a single 30MB episode caused the transfer of over 100MB of data.[…]
The strangest bit of behavior happens when the ranges on these requests reach the end of the file. We were able to consistently see that when the file has completed downloading, it begins downloading again from the beginning of the file and continues for as long as one is streaming the file. This means that, for as long as one is listening to audio being streamed with iOS 6, it is using significant amounts of data. Watch the range headers in this video, which is monitoring the HTTP activity of the stock Podcast app (v1.1.2) on iOS 6.0.0 playing back an episode of This Week in Tech. The file finishes buffering and is completely downloaded at around 0:36.
And in case you’re wondering, no, in fact, there is nothing about podcasting or AV in the iOS 6.0.1 release notes. So if Apple knew (how could they not), they didn’t tell us about it.
What do you need to do? If you’re on iOS 5.0 (because you like Google Maps) or 6.0.1, nothing, you’re all good. If, however, you’re still running iOS 6.0, you need to update…pronto.
For extra fun you can watch this video of the bug in action (the file being downloaded over and over and over again):
Here’s the final word from PRX:
There appears to be a system-wide problem with the AV Foundation framework in iOS 6.0.0, resulting in significantly higher data costs to iPhone users and internet distributors. Users who have not done so should immediately upgrade iOS 6.0.0 devices to iOS 6.0.1, which we can confirm appears to fix the issue on Wifi. While some carriers are offering concessions to customers who may have been affected by this problem, Apple does not appear to have acknowledged the specific issue. The release notes for iOS 6.0.1 mention a change related to Wifi (likely referring to the problem with devices that reported that they were connected to Wifi while connected to 3G and LTE networks), which may be related to the change which fixed this issue.
Do you use the Podcast app? Have you noticed a lot of extra data consumption? Let us know in the comments and if you went over your data limits for the month.