通过swift在IOS中获取AVAudioSynthesiser的音量输出

let audioEngine = AVAudioEngine()

let playerNode = AVAudioPlayerNode()

audioEngine.attach(playerNode)
audioEngine.connect(playerNode, to: audioEngine.mainMixerNode, format: nil)

let buffer = AVAudioPCMBuffer(pcmFormat: playerNode.outputFormat(forBus: 0), frameCapacity: AVAudioFrameCount(playerNode.outputFormat(forBus: 0).sampleRate))

let volumeTapBlock: AVAudioNodeTapBlock = { (buffer, time) in
    guard let channelData = buffer.floatChannelData else { return }
    let channelDataValue = channelData.pointee
    let channelDataValueArray = stride(from: 0, to: Int(buffer.frameLength), by: buffer.stride).map{ channelDataValue[$0] }
    let rms = sqrt(channelDataValueArray.map{ $0 * $0 }.reduce(0, +) / Float(buffer.frameLength))
    print("音量输出：\(rms)")
}

playerNode.installTap(onBus: 0, bufferSize: 1024, format: playerNode.outputFormat(forBus: 0), block: volumeTapBlock)

try? audioEngine.start()

let audioFileURL = Bundle.main.url(forResource: "audio", withExtension: "mp3")!
let audioFile = try! AVAudioFile(forReading: audioFileURL)
playerNode.scheduleFile(audioFile, at: nil)
playerNode.play()