问使用蓝牙耳机时，AVAudioEngine位置音频不工作于.playAndRecord音频会话类别

EN

import AVFoundation


class PlayerRecorder: ObservableObject {
    
    let engine = AVAudioEngine()
    let mixer = AVAudioEnvironmentNode()
    
    init() {
        let audioSession = AVAudioSession.sharedInstance()
        
        /*
         Using .playAndRecord both recording and playback works, however
         the audio that is played is NOT positional. .allowBluetooth is needed
         so that bluetooth headphones can be used.
         */
        try! audioSession.setCategory(.playAndRecord, mode: .default, options: .allowBluetooth)
        
        /*
         Using .playback the positional audio DOES work, however we are not able to record.
         */
        // try! audioSession.setCategory(.playback)
        
        self.engine.attach(self.mixer)
        let stereoFormat =  AVAudioFormat(standardFormatWithSampleRate: self.engine.outputNode.outputFormat(forBus: 0).sampleRate, channels: 2)
        self.engine.connect(self.mixer, to: self.engine.outputNode, format: stereoFormat)
        self.engine.prepare()
        try! self.engine.start()
        
    }
    
    func play() {
        let audioPlayer = AVAudioPlayerNode()
        self.engine.attach(audioPlayer)
        let monoFormat =  AVAudioFormat(standardFormatWithSampleRate: self.engine.outputNode.outputFormat(forBus: 0).sampleRate, channels: 1)
        self.engine.connect(audioPlayer, to: self.mixer, format: monoFormat)
        
        // This file has to be in mono
        let url = Bundle.main.url(forResource: "your-mono-audio-file.mp3", withExtension: nil)
        let f = try! AVAudioFile(forReading: url!)
        audioPlayer.scheduleFile(f, at: nil, completionHandler: nil)
        audioPlayer.renderingAlgorithm = .HRTFHQ
        audioPlayer.position = AVAudio3DPoint(x: 20.0, y: 5.0, z: 0.0)
        audioPlayer.play()
    }
    
}