AVAudioPlayerNode不播放声音

Question

我试着用下面的代码生成声音。一切都是好的，没有错误。但是当我执行这个代码时，没有声音。我怎样才能解决这个问题？

顺便提一下，我用的是这个例子：http://www.tmroyal.com/playing-sounds-in-swift-audioengine.html

var ae:AVAudioEngine
var player:AVAudioPlayerNode?
var mixer:AVAudioMixerNode
var buffer:AVAudioPCMBuffer

ae = AVAudioEngine()
player = AVAudioPlayerNode()
mixer = ae.mainMixerNode;
buffer = AVAudioPCMBuffer(pcmFormat: player!.outputFormat(forBus:0), frameCapacity: 100)
buffer.frameLength = 100

// generate sine wave.
var sr:Float = Float(mixer.outputFormat(forBus:0).sampleRate)
var n_channels = mixer.outputFormat(forBus:0).channelCount

var i:Int=0
while i < Int(buffer.frameLength) {
    var val = sinf(441.0*Float(i)*2*Float(M_PI) / Float(sr))
    buffer.floatChannelData?.pointee[i] = val * 0.5
    i+=Int(n_channels)
}

// setup audio engine
ae.attach(player!)
ae.connect(player!, to: mixer, format: player!.outputFormat(forBus: 0))

ae.prepare()
try! ae.start()
// play player and buffer
player!.scheduleBuffer(buffer, at: nil, options: .loops, completionHandler: nil)
player!.play()

Answer 1

您的AVAudioEngine看起来像是一个局部变量--它将超出作用域并被取消分配。将其分配给类实例变量，您可能会听到一些声音。