AVCapturePhotoOutput crashes at delegate callback on MacOS 13.7.5

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Created Apr ’25

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A functioning Multiplatform app, which includes use of Continuity Camera on an M1MacMini running Sequoia 15.5, works correctly capturing photos with AVCapturePhoto. However, that app (and a test app just for Continuity Camera) crashes at delegate callback when run on a 2017 MacBookPro under MacOS 13.7.5. The app was created with Xcode 16 (various releases) and using Swift 6 (but tried with 5). Compiling and running the test app with Xcode 15.2 on the 13.7.5 machine also crashes at delegate callback.

The iPhone 15 Continuity Camera gets detected and set up correctly, and preview video works correctly. It's when the CapturePhoto code is run that the crash occurs.

The relevant capture code is:

func capturePhoto() {
        let captureSettings = AVCapturePhotoSettings()
        captureSettings.flashMode = .auto
        photoOutput.maxPhotoQualityPrioritization = .quality
        
        photoOutput.capturePhoto(with: captureSettings, delegate: PhotoDelegate.shared)
        print("**** CameraManager: capturePhoto")
    }

and the delegate callbacks are:

class PhotoDelegate: NSObject, AVCapturePhotoCaptureDelegate {
    nonisolated(unsafe) static let shared = PhotoDelegate()
    // MARK: - Delegate callbacks
    func photoOutput(
        _ output: AVCapturePhotoOutput,
        didFinishProcessingPhoto photo: AVCapturePhoto,
        error: (any Error)?
    ) {
        print("**** CameraManager: didFinishProcessingPhoto")
        guard let pData = photo.fileDataRepresentation() else {
            print("**** photoOutput is empty")
            return
        }
        print("**** photoOutput data is \(pData.count) bytes")
    }
    func photoOutput(
        _ output: AVCapturePhotoOutput,
        willBeginCaptureFor resolvedSettings: AVCaptureResolvedPhotoSettings
    ) {
        print("**** CameraManager: willBeginCaptureFor")
    }
    func photoOutput(_ output: AVCapturePhotoOutput, willCapturePhotoFor resolvedSettings: AVCaptureResolvedPhotoSettings) {
        print("**** CameraManager: willCaptureCapturePhotoFor")
    }
}

The crash report significant parts are.....

Crashed Thread:        3  Dispatch queue: com.apple.cmio.CMIOExtensionProviderHostContext

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000000
Exception Codes:       0x0000000000000001, 0x0000000000000000

Termination Reason:    Namespace SIGNAL, Code 11 Segmentation fault: 11
Terminating Process:   exc handler [30850]

VM Region Info: 0 is not in any region.  Bytes before following region: 4296495104
      REGION TYPE                    START - END         [ VSIZE] PRT/MAX SHRMOD  REGION DETAIL
      UNUSED SPACE AT START
--->  
      __TEXT                      100175000-10017f000    [   40K] r-x/r-x SM=COW  ...tinuityCamera

Thread 0::  Dispatch queue: com.apple.main-thread
0   libsystem_kernel.dylib        	    0x7ff803aed552 mach_msg2_trap + 10
1   libsystem_kernel.dylib        	    0x7ff803afb6cd mach_msg2_internal + 78
2   libsystem_kernel.dylib        	    0x7ff803af4584 mach_msg_overwrite + 692
3   libsystem_kernel.dylib        	    0x7ff803aed83a mach_msg + 19
4   CoreFoundation                	    0x7ff803c07f8f __CFRunLoopServiceMachPort + 145
5   CoreFoundation                	    0x7ff803c06a10 __CFRunLoopRun + 1365
6   CoreFoundation                	    0x7ff803c05e51 CFRunLoopRunSpecific + 560
7   HIToolbox                     	    0x7ff80d694f3d RunCurrentEventLoopInMode + 292
8   HIToolbox                     	    0x7ff80d694d4e ReceiveNextEventCommon + 657
9   HIToolbox                     	    0x7ff80d694aa8 _BlockUntilNextEventMatchingListInModeWithFilter + 64
10  AppKit                        	    0x7ff806ca59d8 _DPSNextEvent + 858
11  AppKit                        	    0x7ff806ca4882 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1214
12  AppKit                        	    0x7ff806c96ef7 -[NSApplication run] + 586
13  AppKit                        	    0x7ff806c6b111 NSApplicationMain + 817
14  SwiftUI                       	    0x7ff90e03a9fb 0x7ff90dfb4000 + 551419
15  SwiftUI                       	    0x7ff90f0778b4 0x7ff90dfb4000 + 17578164
16  SwiftUI                       	    0x7ff90e9906cf 0x7ff90dfb4000 + 10340047
17  ContinuityCamera              	       0x10017b49e 0x100175000 + 25758
18  dyld                          	    0x7ff8037d1418 start + 1896

Thread 1:
0   libsystem_pthread.dylib       	    0x7ff803b27bb0 start_wqthread + 0

Thread 2:
0   libsystem_pthread.dylib       	    0x7ff803b27bb0 start_wqthread + 0

Thread 3 Crashed::  Dispatch queue: com.apple.cmio.CMIOExtensionProviderHostContext
0   ???                           	               0x0 ???
1   AVFCapture                    	    0x7ff82045996c StreamAsyncStillCaptureCallback + 61
2   CoreMediaIO                   	    0x7ff813a4358f __94-[CMIOExtensionProviderHostContext captureAsyncStillImageWithStreamID:uniqueID:options:reply:]_block_invoke + 498
3   libxpc.dylib                  	    0x7ff803875b33 _xpc_connection_reply_callout + 36
4   libxpc.dylib                  	    0x7ff803875ab2 _xpc_connection_call_reply_async + 69
5   libdispatch.dylib             	    0x7ff80398b099 _dispatch_client_callout3 + 8
6   libdispatch.dylib             	    0x7ff8039a6795 _dispatch_mach_msg_async_reply_invoke + 387
7   libdispatch.dylib             	    0x7ff803991088 _dispatch_lane_serial_drain + 393
8   libdispatch.dylib             	    0x7ff803991d6c _dispatch_lane_invoke + 417
9   libdispatch.dylib             	    0x7ff80399c3fc _dispatch_workloop_worker_thread + 765
10  libsystem_pthread.dylib       	    0x7ff803b28c55 _pthread_wqthread + 327
11  libsystem_pthread.dylib       	    0x7ff803b27bbf start_wqthread + 15

Of course, the MacBookPro is an old device - but Continuity Camera works with the installed Photo Booth app, so it's possible.

Any thoughts on solving this situation would be appreciated.

Regards, Michaela

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