用AVAudioEngine录制麦克风时如何检测用户停止通话？

import AVFoundation

class AudioRecorder {
    private let audioEngine = AVAudioEngine()
    private let inputNode = AVAudioInputNode()
    private var isRecording = false
    
    func startRecording() {
        guard !isRecording else { return }
        
        let inputFormat = inputNode.inputFormat(forBus: 0)
        let outputFormat = audioEngine.outputNode.outputFormat(forBus: 0)
        
        audioEngine.attach(inputNode)
        audioEngine.connect(inputNode, to: audioEngine.mainMixerNode, format: inputFormat)
        audioEngine.connect(audioEngine.mainMixerNode, to: audioEngine.outputNode, format: outputFormat)
        
        inputNode.installTap(onBus: 0, bufferSize: 1024, format: inputFormat) { (buffer, time) in
            // 处理音频数据，可以在这里进行音量检测
            let volume = self.calculateVolume(buffer: buffer)
            if volume < 0.1 {
                self.stopRecording()
            }
        }
        
        do {
            try audioEngine.start()
            isRecording = true
        } catch {
            print("Failed to start audio engine: \(error.localizedDescription)")
        }
    }
    
    func stopRecording() {
        guard isRecording else { return }
        
        audioEngine.stop()
        inputNode.removeTap(onBus: 0)
        isRecording = false
    }
    
    private func calculateVolume(buffer: AVAudioPCMBuffer) -> Float {
        let floatBuffer = buffer.floatChannelData?[0]
        let bufferLength = UInt32(buffer.frameLength)
        var total: Float = 0
        
        for i in 0..<Int(bufferLength) {
            total += abs(floatBuffer?[i] ?? 0)
        }
        
        let average = total / Float(bufferLength)
        return average
    }
}