I see the same problem but in my case I'm trying to create a Core Audio class using kAudioUnitSubType_RemoteIO for playback,when backgrounded it fails like this:Fails with '!int' error: AudioUnitInitialize() failed. ('!int' == 560557684) [aurioc] AURemoteIO.cpp:1086:Initialize: failed: 560557684(enable 2, outf< 2 ch, 44100 Hz, Int16, inter> inf< 2 ch, 0 Hz, Float32, non-inter>)In foreground it works OK.I've filled a bug report: FB7622685It's important that more people report this problem, eventually it might get fixed (hopefully).I'm sure it's the same error regardless if using AVPlayer or kAudioUnitSubType_RemoteIO. Any high level audio class most probably uses kAudioUnitSubType_RemoteIO under the hood.It would be nice to get a comment from some Apple engineer

I'm quite sure AudioOutputUnitStop is and always have been synchronous.Here is a quite old answer:https://lists.apple.com/archives/coreaudio-api/2005/Dec/msg00042.htmlIf you call AudioOutputUnitStop from the I/O thread then AudioDeviceStop is called immediately. The I/O proc will not be called again. I believe the current I/O cycle's buffer will be played; i.e. that the stop will actually take effect at the end of the I/O cycle. (If I'm wrong, Jeff Moore will correct me...)If you call AudioOutputUnitStop from another thread, then it will call AudioDeviceStop and wait for a notification from the HAL that the hardware has actually stopped before returning. In the interim, the I/O proc may continue to be called.Thus AudioOutputUnitStop is always synchronous; on return, in the absence of an exceptional condition, the I/O proc will not be called again.--Doug WyattCore Audio, Apple

My app is an audio player that has a MPVolumeView. As far as I can tell, the MPVolumeView isn't available when running on a Mac? Is it? At least it's not visible. So that space is empty and in that case I need to use that space for other purposes. And I can't come up with a way to find out if it's displayed or not unless I know if the app is running on a Mac or not. Maybe I'm wrong?

Anyone?

I reported the problem with MPVolumeView to Apple using theFeedback assistant, and here is the reply: "After reviewing your feedback, we have some additional information for you: This is not ARM specific; it’s how MPVolumeView works on Mac. It’s not supported." OK, if it's not supported then it should't be possible to create a MPVolumeView but it is. The one need to find out if an iOS app is running on a Mac so that the space occupied by the MPVolumeView can be used for something else, but how?

Here is one way to check if running on macOS or iOS (plain C code) BOOL IsAppRunningOnMac() {   /* path to the "Documents" folder on iOS:   "/var/mobile/Containers/Data/Application/8C2D631A-DCBB-44FE-8F86-429A89FCE921/Documents" -> iOS path to the "Documents" folder on macOS:   "/Users/USER_NAME/Library/Containers/4EE76C41-2BE8-4A65-B26C-080773E0EB31/Data/Documents"  -> Mac   */ NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0];   // this code might break at some point!   if (![documentsDirectory hasPrefix:@"/var/mobile/"] && ![documentsDirectory hasPrefix:@"/Users/"])     {     // Check that Apple hasn't changed something     assert(0);  // development: notify us by asserting     return NO;  // production: assume iOS     }   return [documentsDirectory hasPrefix:@"/Users/"]; }

Removing the possibility to be able change the speed of Apple Music contents affects many many apps and many many thousands of users. My mailbox was flooded this morning with complaints and customers asking for a refund since my app is now useless. This can't be a bug fix, it's removing of a feature that has been available for at least the last three years, since iOS 13 or even earlier. Please tell us developers that this is actually bug introduced with iOS 15.4 so we can tell our (and Apple's) customers that it will work again in a soon to come update. This isn't what we expect from Apple!

This mornings email complaints about this “bug fix” in iOS 15.4, here we go: // Slowdown/speed up slider no longer working . Music just plays 100% // Speed up/slow down no longer works IPad OS 15.4 // Just updated to iOS 15.4 and now I can’t adjust playback speed of songs from Apple Music. Other imported songs work fine. // Songs in Apple Music cannot change the speed in the app in IOS 15.4. // Why has the slow down stopped working? I seem to be unable to change speeds on any of the music in the library that I’ve been using for more than a year. This just started today. Please help!! // This is ridiculous. The only reason I have your app is to change speeds so I can learn to play them. It’s affected my entire library. What do I do—can I fix it by reinstalling ? // I purchased a new iPhone 13 recently, and I would not have had I realized this would affect my use of Apple Music and your app which I use to practice my fiddle. Please, please fix this problem! // Since I updated to ios 15.4, I found that I can't change the speed, which is very annoying. I thought the app would improve soon after the update. I didn't expect that apple music could not change the speed after the update. I have been using Apple Music play since I bought this app. I hope this problem can be fixed as soon as possible. // My entire library ability to change speed/tempo is now inoperative  // Unable to adjust the speed? Help! // Hey guys - do you think the slow downer will be restored for itunes anytime soon ? // I purchased your app over a year ago and I love it!! I just did the update and realized I can no longer slow down apple music files. Just wondering if you are working on a solution.  // I saw the update regarding tempo and Apple Music. This is the sole reason I use this app. Is there a workaround or a possible fix? This a huge ****… // Hi - hope you can help. For some reason the slide functions of the app no longer works. The loss of sped adjustment is a make problem! Can this be fixed somehow? Have a pushed a button by mistake that prevents this from working? // The speed slider is not working after I downloaded the app // Your app doesn't work slowing song's down anymore. I have an iPhone13. Is this an Apple Music problem?  // I’ve been using this app for many years and it has helped me tremendously as a tap dance teacher. I play all of my music for class through this app. I’ve been having issues with it for the last couple of days. I’m hoping that maybe you are working on the app and that’s why it’s having issues today. The same issues are happening on my iPad and iPhone 12. // Why is the speed adjustment not working with my Apple Music. I have used this feature for my dance class for 2 years. If it truly doesn’t work anymore what options do t have to slow the songs down for practising dances.  Heather  // I’m using your app quite a lot for studying and teaching. I bought the full version of the app from the Apple Store and I’m very happy with it. As you might know, Apple iOS has updated the software. Your app is no longer compatible in all the functions. Please, is there something you can do about it and fix it? Thank you very much for your attention! // What is going on today? I can’t adjust many things on my music, including the speed, which is of course why I have your app, and have for years. Please help! Signed, a really freaked out dance teacher!  // The new update will not let me change music that I have composed, imputed into my iTunes and downloaded to a playlist for your app. I use this function to practice my music at slower tempos especially the improvisation elements of my music. Please tell me this will be repaired?  // The whole reason I bought this app and spent way more on it than the other slow down apps is so I could use it with my purchased Apple Music library. Now I can’t. I would really like my money back but I assume that is not gonna happen. // I can’t change the speed of my music anymore. I read about the bug and the fix. I am paying monthly for Apple Music, does it count to consider I own the music?  I really liked your app as I’m learning piano, but if I can’t slow down the music I have with apple, it is not useful anymore.  How can I fix this while staying with Apple Music? // This is terrible! We are told to constantly keep up with the latest version of iOS software but that has led to critically down grading my favourite app. Please ask Apple to fix.  //

I think it's important that every developer that is affected of this bug should file a bug report and also ask all users that they complain to Apple. Does anybody know where app users should complain?

Does anyone have any new info to share? My bug report is still open and "Recent similar reports" == "None". Many many customers are complaining, I am about to remove my app from the store. Why can't anyone from Apple explain why this change was made? For us developers and all our users, this change does not make sense. It just makes the iOS platform so much worse.

I can also confirm that setting the currentPlaybackRate doesn't work on iOS 16.1 beta 1. Please, we don't want a repeat of the horrible time we had six months ago, our users were crazy.

I filed a bug report back in 2019, FB6489728 Recent Similar Reports:None Resolution:Open MPMusicPlayerController EOF notification. Description: "When the player is set to MPMusicRepeatModeNone: There should be sent a notification when a song reaches EOF file. For my particular use I only enqueue one song and need to know when the songs has ended. MPMusicPlayerControllerPlaybackStateDidChangeNotification and looking for MPMusicPlaybackStateStopped or MPMusicPlaybackStatePaused can be used but it's very hard to to be 100% sure if it was because reaching EOF." // For my app I have solved the problem but with code I don't want anyone to see. Full of heuristic kludge, hard to maintain and can break anytime Apple changes something. A simple EOF notification would solve the problem. And while I'm at it, please add a pitch change setting!!