ARSCNView场景中SCNAudioPlayer音频播放异常问题排查

我正在用ARKit和SceneKit开发AR应用，在ViewController类中遇到了音频播放问题。我在ARSCNView里有一个可旋转移动的立方体SCNNode，想要通过SCNAudioPlayer为该节点添加音频播放功能。

已设置音频源并尝试添加到节点，但场景运行时无音频输出。确认过音频文件sample_audio.mp3路径正确，SCNAudioSource的初始化和加载也没有问题。

简化后的代码 #

import UIKit
import ARKit
import SnapKit
import SceneKit

class ViewController: UIViewController {

    // MARK: - Property
    
    // MARK: - execute
    private func execute() {
        action_example1()
    }
    
    // MARK: - UIComponents
    private lazy var arSceneView: ARSCNView = {
        $0.delegate = self
        $0.showsStatistics = true
        return $0
    }(ARSCNView())
}

extension ViewController {
    func action_example1() {
        let scene = SCNScene()
        arSceneView.scene = scene

        let boxGeometry = SCNBox(width: 1, height: 1, length: 1, chamferRadius: 0.1)
        
        var boxNode = SCNNode()
        boxNode = SCNNode(geometry: boxGeometry)
        boxNode.position = SCNVector3(0, 0, -5)
        
        let material = SCNMaterial()
//        material.diffuse.contents = UIImage(resource: .pyramidFull)
        
        boxNode.geometry?.firstMaterial = material
        scene.rootNode.addChildNode(boxNode)

        let rotateAction = SCNAction.rotateBy(x: 0, y: .pi, z: 0, duration: 2)
        let moveAction = SCNAction.move(to: SCNVector3(0, 0, +10), duration: 2)
        let sequenceAction = SCNAction.sequence([rotateAction, moveAction])
        let repeatAction = SCNAction.repeatForever(sequenceAction)
        
        
        let audioSource = SCNAudioSource(fileNamed: "sample_audio.mp3")!
        audioSource.loops = true
        boxNode.runAction(SCNAction.playAudio(audioSource, waitForCompletion: false))
        audioSource.load()
        
        
        boxNode.runAction(repeatAction)
    }
}

extension ViewController: ARSCNViewDelegate {
    
    // MARK: - ARSCNViewDelegate
    
/*
    // Override to create and configure nodes for anchors added to the view's session.
    func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
        print(#function)
        let node = SCNNode()
        
        return node
    }
*/
    
    func session(_ session: ARSession, didFailWithError error: Error) {
        // Present an error message to the user
        print(#function)
        
    }
    
    func sessionWasInterrupted(_ session: ARSession) {
        // Inform the user that the session has been interrupted, for example, by presenting an overlay
        print(#function)
    }
    
    func sessionInterruptionEnded(_ session: ARSession) {
        // Reset tracking and/or remove existing anchors if consistent tracking is required
        print(#function)
    }
}

已尝试的解决步骤 #

• 创建SCNAudioSource实例并设置loops = true
• 调用load()方法确保音频源加载完成
• 通过playAudio动作添加音频播放逻辑

预期音频会随SCNNode的动画持续播放，但实际无音频输出，想问有没有遗漏的配置或额外操作需要执行？

问题排查与解决方案 #

1. 调整音频加载与播放的顺序
   你的代码中先执行了播放动作，再调用audioSource.load()，这会导致音频还未加载完成就触发播放，自然没有声音。需要先加载音频源，再执行播放动作：

   let audioSource = SCNAudioSource(fileNamed: "sample_audio.mp3")!
   audioSource.loops = true
   audioSource.load() // 先完成加载
   boxNode.runAction(SCNAction.playAudio(audioSource, waitForCompletion: false)) // 再执行播放
   

2. 配置AVAudioSession
   AR应用默认可能未激活音频会话，需要手动配置以确保音频正常输出。在action_example1方法开头添加以下代码，记得先导入AVFoundation框架：

   import AVFoundation
   

   do {
       try AVAudioSession.sharedInstance().setCategory(.playback, mode: .default)
       try AVAudioSession.sharedInstance().activate()
   } catch {
       print("音频会话配置失败: \(error)")
   }
   

3. 改用SCNAudioPlayer直接绑定节点
   除了SCNAction的方式，直接给节点添加SCNAudioPlayer组件会更稳定，音频会自动跟随节点生命周期播放：

   let audioSource = SCNAudioSource(fileNamed: "sample_audio.mp3")!
   audioSource.loops = true
   audioSource.load()
   let audioPlayer = SCNAudioPlayer(source: audioSource)
   boxNode.addAudioPlayer(audioPlayer)
   

4. 关闭音频空间化（可选）
   SceneKit默认会根据节点与相机的距离调整音量，如果节点移动后距离过远，可能导致音量衰减为0。可以关闭空间化效果强制播放：

   audioSource.isSpatialized = false
   

内容的提问来源于stack exchange，提问作者StrongMan