AVAudioRecorder 仅适用于.record(forDuration:)

Question

For the life of me I have not been able to get AVAudioRecorder to properly record sound with the record() method. I can only get sound to record if I use the record(forDuration:) method. I've tried across multiple devices (iPhone 8 w/ iOS 14, iPad Air (7th gen) w/ iOS 14, iPhone 12 mini simulator). I've also changed the build target from iOS 13 to iOS 9 and tried on older simulators (iPhone 8 w/ iOS 10).

Regardless, of my device/iOS combination the behavior is always the same - when stopping the recording record() always produces an empty 4kb audio file. I've explored the simulator containers, and downloaded the device containers to verify this. Again, record(forDuration:) will save a proper audio file with the actual recorded sound.

Xcode Version: 12.3

Culprit code:

func recordAudio() {
        let dirPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String
        let recordingName = "recordedVoice.m4a"
        let pathArray = [dirPath, recordingName]
        let filePath = URL(string: pathArray.joined(separator: "/"))
        
        let session = AVAudioSession.sharedInstance()
        try! session.setCategory(.playAndRecord, mode: .default, options: .defaultToSpeaker)
        try! session.setActive(true)
        
        try! self.audioRecorder = AVAudioRecorder(url: filePath!, settings: [:])
        self.audioRecorder.delegate = self
        self.audioRecorder.isMeteringEnabled = true
        self.audioRecorder.prepareToRecord()

        // Problematic section
        // I only use one of the following two lines, record() fails, record(forDuration:) works.
        self.audioRecorder.record()
        self.audioRecorder.record(forDuration: 5)
}

func stopRecord() {
        self.audioRecorder.stop()
        let audioSession = AVAudioSession.sharedInstance()
        try! audioSession.setActive(false)
}

Silent failure for record() - no Errors or crashes.

Another interesting thing to note that I just discovered. When I call audioRecorder.stop() the app fails to save the audio file properly. Regardless of whether I use record() or record(forDuration:)

I'm very confused. Any help is appreciated.

Answer 1

Silent failure for record() - no Errors or crashes.

I get a 'fmt?' error when instantiating the AVAudioRecorder . Providing a settings dictionary fixes it.

let settings = [
    AVFormatIDKey: kAudioFormatMPEG4AAC,
    AVSampleRateKey: 44100,
    AVNumberOfChannelsKey: 1
]

try! self.audioRecorder = AVAudioRecorder(url: filePath!, settings: settings)