Flutter: Problem with Audio_Service after upgrade to iOS 16.2 - flutter

Question

After I updated my iPhone to iOS 16.2 I encountered a problem that I don't have with another iPhone that has iOS 14 installed. Songs that used to go in the background now only go in the foreground. As a player I use just audio. This problem does not occur with Android. I don't see any programming problems otherwise the problem would also occur with the iPhone that has iOS 14 installed, whereas with this iPhone everything works correctly, as before.
In the console I have no error message apart from the one it has always given but has never been a problem.
[NowPlaying] [MRNowPlaying] Ignoring setPlaybackState because application does not contain entitlement com.apple.mediaremote.set-playback-state for platform
Now I would say this has been added but I don't remember if it was there before.
[Entitlements] MSVEntitlementUtilities - Process Runner PID[572] - Group: (null) - Entitlement: com.apple.mediaremote.external-artwork-validation - Entitled: NO - Error: (null)
With another simpler app with iOS 16.2 I have the same problem, and I also noticed an error message that may help find the problem
[BackgroundTask] Background Task 9 ("Flutter debug task"), was created over 30 seconds ago. In applications running in the background, this creates a risk of termination. Remember to call UIApplication.endBackgroundTask(_:) for your task in a timely manner to avoid this.
So now the audio can be heard perfectly in the foreground but if I put the app in the background when changing audio files the audio stops. This problem wasn't there before, and the fact that it works perfectly with iOS 14 suggests a problem with the iOS 16.2 update.
My Doctor -v
[✓] Flutter (Channel stable, 3.3.10, on macOS 12.6.2 21G320 darwin-x64, locale it-IT)
• Flutter version 3.3.10 on channel stable at /Users/carlosacchetti/Developer/flutter
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• Build 14C18
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[✓] Connected device (4 available)
• SM G780G (mobile) • RF8T30H0K2Y • android-arm64 • Android 13 (API 33)
• iPhone CS (mobile) • 00008110-000A5CD42682801E • ios • iOS 16.2 20C65
• macOS (desktop) • macos • darwin-x64 • macOS 12.6.2 21G320 darwin-x64
• Chrome (web) • chrome • web-javascript • Google Chrome 108.0.5359.124
! Error: iPhone CS is busy: Fetching debug symbols for iPhone CS. Xcode will continue when iPhone CS is finished. (code -10)
! Error: Apple Watch di Carlo needs to connect to determine its availability. Check the connection between the device and its
companion iPhone, and the connection between the iPhone and Xcode. Both devices may also need to be restarted and unlocked.
(code 1)
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• No issues found!

Answer 1

#csacchetti I had a similar issue.
I'm mimicking the playlist behaviour but not using the ConcatenatingAudioSource, just switching tracks manually calling player.setAudioSource() with the proper index, and listening to the "completed" playbackState in order to skip to the next index.
Since I was using the player's 'LoopMode.off', after the 'completed' state was emitted, an 'idle' state was emitted as well. I think broadcasting this 'idle' state in iOS 16 might close the audio session.
I don't know if this is exactly what's happening, and I can't explain why it didn't occur in the previous iOS versions. But this fixed it for me.
Try to broadcast AudioProcessingState.ready when you get a ProcessingState.idle, so that the OS keep your session alive while you switch tracks:
processingState: {
ProcessingState.idle: Platform.isIOS ? AudioProcessingState.ready : AudioProcessingState.idle,
ProcessingState.loading: AudioProcessingState.loading,
ProcessingState.buffering: AudioProcessingState.buffering,
ProcessingState.ready: AudioProcessingState.ready,
ProcessingState.completed: AudioProcessingState.completed,
}[_player.processingState]!,