使用两个不同的滑块设置左右耳机音量

Posted 2023-02-23

【中文标题】使用两个不同的滑块设置左右耳机音量

【英文标题】：Set left and right headphone volume using two different sliders

【发布时间】：2020-12-09 19:11:24

【问题描述】：

我正在生成不同频率的波声，用户应该只使用耳机听到这种波声，他/她将。为了实现波浪声音，我在下面编写了完美的代码。 但问题是：从过去 5 天开始，我尝试分别设置左右耳机的音量，但没有成功。

class Synth 

// MARK: Properties
public static let shared = Synth()

public var volume: Float 
    set 
        audioEngine.mainMixerNode.outputVolume = newValue
    
    get 
        audioEngine.mainMixerNode.outputVolume
    


public var frequencyRampValue: Float = 0

public var frequency: Float = 440 
    didSet 
        if oldValue != 0 
            frequencyRampValue = frequency - oldValue
         else 
            frequencyRampValue = 0
        
    


private var audioEngine: AVAudioEngine

private lazy var sourceNode = AVAudiosourceNode  _, _, frameCount, audioBufferList in
    let ablPointer = UnsafeMutableAudioBufferListPointer(audioBufferList)
            
    let localRampValue = self.frequencyRampValue
    let localFrequency = self.frequency - localRampValue
    
    let period = 1 / localFrequency

    for frame in 0..<Int(frameCount) 
        let percentComplete = self.time / period
        let sampleVal = self.signal(localFrequency + localRampValue * percentComplete, self.time)
        self.time += self.deltaTime
        self.time = fmod(self.time, period)
        
        for buffer in ablPointer 
            let buf: UnsafeMutableBufferPointer<Float> = UnsafeMutableBufferPointer(buffer)
            buf[frame] = sampleVal
        
    
    
    self.frequencyRampValue = 0
    
    return noErr


private var time: Float = 0
private let sampleRate: Double
private let deltaTime: Float

private var signal: Signal

// MARK: Init

init(signal: @escaping Signal = Oscillator.square) 
    
    audioEngine = AVAudioEngine()
    let mainMixer = audioEngine.mainMixerNode
    let outputNode = audioEngine.outputNode
    let format = outputNode.inputFormat(forBus: 0)
    
    sampleRate = format.sampleRate
    deltaTime = 1 / Float(sampleRate)
    
    self.signal = signal
    
    let inputFormat = AVAudioFormat(commonFormat: format.commonFormat,
                                    sampleRate: format.sampleRate,
                                    channels: 1,
                                    interleaved: format.isInterleaved)
    
    audioEngine.attach(sourceNode)
    audioEngine.connect(sourceNode, to: mainMixer, format: inputFormat)
    audioEngine.connect(mainMixer, to: outputNode, format: nil)
    mainMixer.outputVolume = 0
    audioEngine.mainMixerNode.pan = 100 // this does not work, 
    //audioEngine.mainMixerNode.pan = 1.0 // this also does not work
    do 
        try audioEngine.start()
     catch 
        print("Could not start engine: \(error.localizedDescription)")
    
    


//This function will be called in view controller to generate sound
public func setWaveformTo(_ signal: @escaping Signal) 
    self.signal = signal

使用上面的代码，我可以在左右耳机中正常听到波声。 我尝试将 audioEngine.mainMixerNode.pan 用于值 100 和 -100 以及 -1.0 和 1.0 但这并没有做出任何改变。

【问题讨论】：

我看不到您在代码中的任何位置设置pan。如果你能证明这一点会有所帮助。

我已经更新了代码，请检查。 （在连接语句之后）

【参考方案1】：

我尝试将 audioEngine.mainMixerNode.pan 用于值 100 和 -100，但这并没有做出任何改变。

pan value 的允许范围是 -1.0, 1.0。您说您使用的值超出了该范围，因此它们没有效果也就不足为奇了。请改用 0.75 或 -0.75。

【讨论】：

您是否将其称为左侧的 audioEngine.mainMixerNode.pan = -1.0 和右侧的 audioEngine.mainMixerNode.pan = 1.0？请详细说明。