如何在iOS Swift中设置10个频段的AVAudioUnitEQ均衡器预设增益值

Question

我可以添加音频设置，以通过

更改滑块值来更改均衡器

let FREQUENCY: [Float] = [31, 62, 125, 250, 500, 1000, 2000, 4000, 8000, 16000]
//let FREQUENCY: [Float] = [60, 230, 910, 3600, 14000]

self.audioEngine = AVAudioEngine.init()
self.audioPlayerNode = AVAudioPlayerNode.init()
self.audioUnitEQ = AVAudioUnitEQ(numberOfBands: 10)
self.audioEngine.attach(self.audioPlayerNode)
self.audioEngine.attach(self.audioUnitEQ)        

for i in 0...9 {
    self.audioUnitEQ.bands[i].filterType = .parametric
    self.audioUnitEQ.bands[i].frequency = FREQUENCY[i]
    self.audioUnitEQ.bands[i].bandwidth = 0.5 // half an octave
    let eq = self.value(forKey: String(format: "eq%d", i)) as! UISlider
    self.audioUnitEQ.bands[i].gain = eq.value
    self.audioUnitEQ.bands[i].bypass = false
}

但是有什么方法可以更改增益值或设置均衡器预设，例如声学，摇滚等。如何为这些预设设置增益值