ios - AVAudioSession 无法识别来自蓝牙设备的音频

Question

我正在使用 AVAudioSession 来收听语音输入。它适用于有线耳机，但不适用于连接的蓝牙设备。以下是我用来设置蓝牙麦克风输入的代码

func setupSessionForRecording() {
    let audioSession = AVAudioSession.sharedInstance()
    do {
        try audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord, with: [.allowBluetooth]) 
    } catch let error as NSError   {
        debugPrint("Error in listening "+error.localizedDescription)
    }
    var inputsPriority: [(type: String, input: AVAudioSessionPortDescription?)] = [
        (AVAudioSessionPortLineIn, nil),
        (AVAudioSessionPortHeadsetMic, nil),
        (AVAudioSessionPortBluetoothHFP, nil),
        (AVAudioSessionPortUSBAudio, nil),
        (AVAudioSessionPortCarAudio, nil),
        (AVAudioSessionPortBuiltInMic, nil),
        ]
    for availableInput in audioSession.availableInputs! {
        guard let index = inputsPriority.index(where: { $0.type == availableInput.portType }) else { continue }
        inputsPriority[index].input = availableInput
    }
    guard let input = inputsPriority.filter({ $0.input != nil }).first?.input else {
        fatalError("No Available Ports For Recording")
    }
    do {
        try audioSession.setPreferredInput(input)
        try audioSession.setMode(AVAudioSessionModeMeasurement)
        try audioSession.setActive(true, with: .notifyOthersOnDeactivation)
        try audioSession.setPreferredIOBufferDuration(10)
    } catch {
        fatalError("Error Setting Up Audio Session")
    }
}

此代码停止从设备麦克风接收输入，我还在蓝牙耳机中听到它已准备好收听的声音，但它没有从设备接收任何输入。

此外，

当我尝试在蓝牙耳机中播放任何音频时，它不起作用。这是播放音频的代码

        do {
            let output = AVAudioSession.sharedInstance().currentRoute.outputs[0].portType
            if output == "Receiver" || output == "Speaker"{
                try AVAudioSession.sharedInstance().overrideOutputAudioPort(.speaker)
            }
            else{
                try AVAudioSession.sharedInstance().overrideOutputAudioPort(.none)
            }
            print("Voice Out \(output)" )
        } catch let error as NSError {
            print("audioSession error: \(error.localizedDescription)")
            os_log("Error during changing the current audio route: %@"    , log: PollyVoiceViewController.log, type: .error, error)
        } catch {
            os_log("Unknown error during changing the current audio route", log: PollyVoiceViewController.log, type: .error)
        }
        do {
            let soundData =  try Data(contentsOf: url as URL)
            self.audioPlayer = try AVAudioPlayer(data: soundData)
            self.audioPlayer?.prepareToPlay()
            self.audioPlayer?.volume = 3.0
            self.audioPlayer?.delegate = self
            self.audioPlayer?.play()
        } catch let error as NSError {
            print("Error getting the audio file"+error.description)
        }

Answer 1

原因是:BluetoothHFP 在AVAudioSessionModeMeasurement 模式下不可用

AVAudioSessionModeMeasurement

设置try audioSession.setMode(AVAudioSessionModeMeasurement)后，audioSession.availableInputs不包含BluetoothHFP。

This mode is intended for apps that need to minimize the amount of system-supplied signal processing to input and output signals. If recording on devices with more than one built-in microphone, the primary microphone is used.

并且在setPreferredInput(_:)的文档中

AVAudioSessionPortDescription 必须在 availableInputs 数组中。

The value of the inPort parameter must be one of the AVAudioSessionPortDescription objects in the availableInputs array. If this parameter specifies a port that is not already part of the current audio route and the app’s session controls audio routing, this method initiates a route change to use the preferred port.

并且必须在设置模式后设置。

You must set a preferred input port only after setting the audio session’s category and mode and activating the session.