使用 AVAudioEngine 的详细信息

Question

背景：我发现了一个名为“实践中的 AVAudioEngine”的 Apple WWDC 会议，并正在尝试制作类似于 43:35 (https://youtu.be/FlMaxen2eyw?t=2614) 显示的上一个演示的内容。我使用的是 SpriteKit 而不是 SceneKit，但原理是一样的：我想生成球体，将它们扔来扔去，当它们碰撞时，引擎会播放每个球体独有的声音。

问题：

• 我想要一个唯一的 AudioPlayerNode 附加到每个 SpriteKitNode，以便我可以为每个球体播放不同的声音。即现在，如果我创建两个球体并为它们的每个 AudioPlayerNode 设置不同的音高，即使原始球体发生碰撞，似乎也只有最近创建的 AudioPlayerNode 正在播放。在演示期间，他提到“我正在为每个球绑定一个球员，一个专注的球员”。我该怎么做呢？

• 每次发生新的碰撞时都会出现音频点击/伪影。我假设这与 AVAudioPlayerNodeBufferOptions 和/或我试图在每次发生联系时非常快速地创建、调度和使用缓冲区的事实有关，这不是最有效的方法。对此有什么好的解决方法？

代码：如视频中所述，“...对于每个诞生在这个世界上的球，也会创建一个新的玩家节点”。我有一个单独的球体类，它有一个返回 SpriteKitNode 的方法，并且每次调用它时都会创建一个 AudioPlayerNode：

class Sphere {

    var sphere: SKSpriteNode = SKSpriteNode(color: UIColor(), size: CGSize())
    var sphereScale: CGFloat = CGFloat(0.01)
    var spherePlayer = AVAudioPlayerNode()
    let audio = Audio()
    let sphereCollision: UInt32 = 0x1 << 0

    func createSphere(position: CGPoint, pitch: Float) -> SKSpriteNode {

        let texture = SKTexture(imageNamed: "Slice")
        let collisionTexture = SKTexture(imageNamed: "Collision")

        // Define the node

        sphere = SKSpriteNode(texture: texture, size: texture.size())

        sphere.position = position
        sphere.name = "sphere"
        sphere.physicsBody = SKPhysicsBody(texture: collisionTexture, size: sphere.size)
        sphere.physicsBody?.dynamic = true
        sphere.physicsBody?.mass = 0
        sphere.physicsBody?.restitution = 0.5
        sphere.physicsBody?.usesPreciseCollisionDetection = true
        sphere.physicsBody?.categoryBitMask = sphereCollision
        sphere.physicsBody?.contactTestBitMask = sphereCollision
        sphere.zPosition = 1

        // Create AudioPlayerNode

        spherePlayer = audio.createPlayer(pitch)

        return sphere    
    }

这是我创建 AudioPCMBuffers 和 AudioPlayerNodes 的音频类

class Audio {

let engine: AVAudioEngine = AVAudioEngine()

func createBuffer(name: String, type: String) -> AVAudioPCMBuffer {

    let audioFilePath = NSBundle.mainBundle().URLForResource(name as String, withExtension: type as String)!
    let audioFile = try! AVAudioFile(forReading: audioFilePath)
    let buffer = AVAudioPCMBuffer(PCMFormat: audioFile.processingFormat, frameCapacity: UInt32(audioFile.length))
    try! audioFile.readIntoBuffer(buffer)

    return buffer
}

func createPlayer(pitch: Float) -> AVAudioPlayerNode {

    let player = AVAudioPlayerNode()
    let buffer = self.createBuffer("PianoC1", type: "wav")
    let pitcher = AVAudioUnitTimePitch()
    let delay = AVAudioUnitDelay()
    pitcher.pitch = pitch
    delay.delayTime = 0.2
    delay.feedback = 90
    delay.wetDryMix = 0

    engine.attachNode(pitcher)
    engine.attachNode(player)
    engine.attachNode(delay)

    engine.connect(player, to: pitcher, format: buffer.format)
    engine.connect(pitcher, to: delay, format: buffer.format)
    engine.connect(delay, to: engine.mainMixerNode, format: buffer.format)

    engine.prepare()
    try! engine.start()

    return player
}  
}

然后在我的 GameScene 类中测试碰撞，安排缓冲区并在发生接触时播放 AudioPlayerNode

 func didBeginContact(contact: SKPhysicsContact) {

        let firstBody: SKPhysicsBody = contact.bodyA

        if (firstBody.categoryBitMask & sphere.sphereCollision != 0) {

        let buffer1 = audio.createBuffer("PianoC1", type: "wav")
        sphere.spherePlayer.scheduleBuffer(buffer1, atTime: nil, options: AVAudioPlayerNodeBufferOptions.Interrupts, completionHandler: nil)
        sphere.spherePlayer.play()

        }
}

我是 Swift 新手，只有基本的编程知识，因此欢迎提出任何建议/批评。

Answer 1

我一直在使用 scenekit 中的 AVAudioEngine 并尝试做其他事情，但这将是您正在寻找的：

https://developer.apple.com/library/mac/samplecode/AVAEGamingExample/Listings/AVAEGamingExample_AudioEngine_m.html

它解释了以下过程： 1-实例化你自己的 AVAudioEngine 子类 2-为每个 AVAudioPlayer 加载 PCMBuffers 的方法 3-更改环境节点的参数以适应大量弹球对象的混响

编辑：转换、测试并添加了一些功能：

1-您创建一个 AVAudioEngine 的子类，例如将其命名为 AudioLayerEngine。这是为了访问 AVAudioUnit 效果，例如失真、延迟、音高和许多其他可用作 AudioUnit 的效果。 2-通过为音频引擎设置一些配置来初始化，例如渲染算法，暴露 AVAudioEnvironmentNode 以播放 SCNNode 对象或 SKNode 对象的 3D 位置（如果您处于 2D 中但想要 3D 效果） 3-创建一些辅助方法来为您想要的每个 AudioUnit 效果加载预设 4-创建一个辅助方法来创建音频播放器，然后将其添加到您想要的任何节点，因为 SCNNode 接受返回 [AVAudioPlayer] 或 [SCNAudioPlayer] 的 .audioPlayers 方法 5-开始播放。

我已经粘贴了整个类以供参考，以便您可以根据需要对其进行构建，但请记住，如果您将其与 SceneKit 或 SpriteKit 耦合，则使用此音频引擎来管理您的所有声音，而不是 SceneKit 的内部 AVAudioEngine。这意味着您在 AwakeFromNib 方法期间在 gameView 中实例化它

import Foundation
import SceneKit
import AVFoundation

class AudioLayerEngine:AVAudioEngine{
    var engine:AVAudioEngine!
    var environment:AVAudioEnvironmentNode!
    var outputBuffer:AVAudioPCMBuffer!
    var voicePlayer:AVAudioPlayerNode!
    var multiChannelEnabled:Bool!
    //audio effects
    let delay = AVAudioUnitDelay()
    let distortion = AVAudioUnitDistortion()
    let reverb = AVAudioUnitReverb()

    override init(){
        super.init()
engine = AVAudioEngine()
environment = AVAudioEnvironmentNode()

engine.attachNode(self.environment)
voicePlayer = AVAudioPlayerNode()
engine.attachNode(voicePlayer)
voicePlayer.volume = 1.0
        outputBuffer = loadVoice()
        wireEngine()
        startEngine()
voicePlayer.scheduleBuffer(self.outputBuffer, completionHandler: nil)
voicePlayer.play()
    }

    func startEngine(){
        do{
            try engine.start()
        }catch{
            print("error loading engine")
        }
    }

    func loadVoice()->AVAudioPCMBuffer{
        let URL = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("art.scnassets/sounds/interface/test", ofType: "aiff")!)
        do{
            let soundFile = try AVAudioFile(forReading: URL, commonFormat: AVAudioCommonFormat.PCMFormatFloat32, interleaved: false)
             outputBuffer = AVAudioPCMBuffer(PCMFormat: soundFile.processingFormat, frameCapacity: AVAudioFrameCount(soundFile.length))
            do{
            try soundFile.readIntoBuffer(outputBuffer)
            }catch{
                print("somethign went wrong with loading the buffer into the sound fiel")
            }
            print("returning buffer")
            return outputBuffer
        }catch{
        }
        return outputBuffer
    }

    func wireEngine(){
loadDistortionPreset(AVAudioUnitDistortionPreset.MultiCellphoneConcert)
        engine.attachNode(distortion)
        engine.attachNode(delay)
engine.connect(voicePlayer, to: distortion, format: self.outputBuffer.format)
        engine.connect(distortion, to: delay, format: self.outputBuffer.format)
                engine.connect(delay, to: environment, format: self.outputBuffer.format)
        engine.connect(environment, to: engine.outputNode, format: constructOutputFormatForEnvironment())

    }

    func constructOutputFormatForEnvironment()->AVAudioFormat{
let outputChannelCount = self.engine.outputNode.outputFormatForBus(1).channelCount
let hardwareSampleRate = self.engine.outputNode.outputFormatForBus(1).sampleRate
let environmentOutputConnectionFormat = AVAudioFormat(standardFormatWithSampleRate: hardwareSampleRate, channels: outputChannelCount)
multiChannelEnabled = false
        return environmentOutputConnectionFormat
    }

    func loadDistortionPreset(preset: AVAudioUnitDistortionPreset){
        distortion.loadFactoryPreset(preset)
}

    func createPlayer(node: SCNNode){
        let player = AVAudioPlayerNode()
distortion.loadFactoryPreset(AVAudioUnitDistortionPreset.SpeechCosmicInterference)
engine.attachNode(player)
engine.attachNode(distortion)
engine.connect(player, to: distortion, format: outputBuffer.format)
        engine.connect(distortion, to: environment, format: constructOutputFormatForEnvironment())
let algo = AVAudio3DMixingRenderingAlgorithm.HRTF
        player.renderingAlgorithm = algo
        player.reverbBlend = 0.3
        player.renderingAlgorithm = AVAudio3DMixingRenderingAlgorithm.HRTF
    }

}