App Crash, "Lost Connection"

Question

Similar to this this question,

I am having issues and my app is crashing in the same way. I would assume the same answer as on the other question: memory issue; except I am getting the crash during an AVAssetExportSession call.

guard let exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality) else { return }
        exporter.outputFileType = AVFileTypeMPEG4
        exporter.outputURL = url
        exporter.videoComposition = mainComposition
        print("done")

        exporter.exportAsynchronously(completionHandler: {
            DispatchQueue.main.async(execute: {
                self.exportDidFinish(exporter)
                print("removing AI")
                self.removeAI()
                print("removed AI")
                completion()
            })
        })

func exportDidFinish(_ exporter:AVAssetExportSession) {
    if(exporter.status == AVAssetExportSessionStatus.completed) {
        print("cool")
    }
    else if(exporter.status == AVAssetExportSessionStatus.failed) {
        print(exporter.error as Any)
    }
}

It prints "done" but it never prints "removing AI". It also doesn't print "cool" or "(error)"; it crashes and says at the top of XCode "Lost connection to iPhone..." just as the other question states.

I would assume it is a memory issue, but there is nothing happening in between (to my knowledge of how this works) during the asynchronous exporting as I am just waiting for the completion handler to be called. But nothing gets called in between and I am unsure how to handle this. Any thoughts?

Answer 1

I think that AVAssetExportSession object may be deallocated while running async task. Consider put it as a class variable to make sure that async block can finish it's task. It will be something like:

class myClass {
    var exporter: AVAssetExportSession?

    func export() {
        exporter = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetHighestQuality)
        guard exporter != nil else { return }
        exporter.outputFileType = AVFileTypeMPEG4
        exporter.outputURL = url
        exporter.videoComposition = mainComposition
        print("done")

        exporter?.exportAsynchronously(completionHandler: { 
            DispatchQueue.main.async {
               self.exportDidFinish(exporter)
               print("removing AI")
               self.removeAI()
               print("removed AI")
               completion()
           }
        }
    }
}

I'm really not sure why you also put everything on a main thread in completion block, but maybe you want to do something with UI later, so I leave it there.

But most import is - make your AVAssetExportSession not stored on method that may dealloc it. It's a memory issue that could cause this.

Answer 2

I had this issue before, it wasn't a memory issue for me. I don't know how exactly I got resolved, but I these are the things I did:

I deleted the app, hard reset the phone, cleaned build on Xcode, restarted Xcode, deleted derived data, and if I remember correctly changed the USB port until it got fixed.

I also had console and a VM open, I closed them as well.