IOS app crashes with "required condition is false: IsFormatSampleRateAndChannelCountValid(format)'" when the mic is selected

Question

I am getting an application crash of my app when I am using mic in my case Microsoft Teams on the background and trying to record an audio inside of my app.

Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'required condition is false: IsFormatSampleRateAndChannelCountValid(format)'

Please refer to the code below:

func startRecording() {
        
        // Clear all previous session data and cancel task
        if recognitionTask != nil {
            recognitionTask?.cancel()
            recognitionTask = nil
        }

        // Create instance of audio session to record voice
        let audioSession = AVAudioSession.sharedInstance()
        do {
            try audioSession.setCategory(AVAudioSession.Category.record, mode: AVAudioSession.Mode.measurement, options: AVAudioSession.CategoryOptions.defaultToSpeaker)
            try audioSession.setActive(true, options: .notifyOthersOnDeactivation)
        } catch {
            print("audioSession properties weren't set because of an error.")
        }
    
        self.recognitionRequest = SFSpeechAudioBufferRecognitionRequest()

        let inputNode = audioEngine.inputNode

        guard let recognitionRequest = recognitionRequest else {
            fatalError("Unable to create an SFSpeechAudioBufferRecognitionRequest object")
        }

        recognitionRequest.shouldReportPartialResults = true

        self.recognitionTask = speechRecognizer?.recognitionTask(with: recognitionRequest, resultHandler: { (result, error) in

            var isFinal = false

            if result != nil {

                self.textField.text = result?.bestTranscription.formattedString
                isFinal = (result?.isFinal)!
            }

            if error != nil || isFinal {

                self.audioEngine.stop()
                inputNode.removeTap(onBus: 0)

                self.recognitionRequest = nil
                self.recognitionTask = nil

                self.micButton.isEnabled = true
            }
        })
    
        let recordingFormat = inputNode.outputFormat(forBus: 0)

    
        inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer, when) in
            self.recognitionRequest?.append(buffer)
        }

        self.audioEngine.prepare()

        do {
            try self.audioEngine.start()
        } catch {
            print("audioEngine couldn't start because of an error.")
        }

        self.textField.text = ""
    }

I am pretty sure that the problem is somewhere here, but not sure how to fix it.

let recordingFormat = inputNode.outputFormat(forBus: 0)
        inputNode.installTap(onBus: 0, bufferSize: 1024, format: recordingFormat) { (buffer, when) in
            self.recognitionRequest?.append(buffer)
        }

Answer 1

I had the same problem while following the Scrumdinger tutorial on the Apple Developer site. Finally I found a comment by some guy on a similar problem. It turned out that his development machine has no mic. That explains why the tutorial code works fine on my iPhone.

Then I connected my iPhone to my Mac Mini as a webcam. After that, both the preview and simulator worked smoothly. I cannot find the post with that comment, but the credit for this answer and my thanks go to the anonymous guy who posted it.