Starting some time during the iOS 17 beta period, I've been seeing unusual playback rate behavior. I have an app that configures a queue of tracks to play and then sets the playback rate at the start of each new track, getting notified of each new track by observing MPMusicPlayerControllerNowPlayingItemDidChange.
In iOS 17, I've noticed that setting the playback rate while an app is in the background will not actually change the playback rate. It appears to, and MusicPlayer.state.playbackRate returns the playback rate that has been requested, but the actual playback rate remains at whatever value it was previously. This is not the case when the app is in the foreground, setting the playback rate works as you would expect, updating the actual rate of playback as well as the value returned from the MusicPlayer.
In iOS 16, these playback rate changes would occur normally, regardless of the state of the app in the foreground or background.
Given the incorrect rate information coming back from the MusicPlayer state, this would appear to be an unexpected change.
I've looked in the SDK diffs for any intentional changes for how playbackRate works and I haven't seen anything new or any new tech notes on the subject. Has anyone seen anything like this in their own implementations?