如何从 ARSKView（或 SKView）帧创建视频，包括微音频（ios 11）

Posted 2023-03-10

【中文标题】如何从 ARSKView（或 SKView）帧创建视频，包括微音频（ios 11）

【英文标题】：How to create a video from ARSKView (or SKView) frames, including micro audio (ios 11)

【发布时间】：2017-06-22 16:00:10

【问题描述】：

我正在使用 ARKit，我想从 ARSKView 帧创建视频。 我尝试使用 ReplayKit，但行为不是我所期望的： - 我不想记录整个屏幕。 - 我不希望用户被提示我们正在录制屏幕。

另外，如何结合微输入和视频？我猜音频没有在 ARSKView 中流式传输？ 这是代码（来自 Apple 示例）：

import UIKit
import SpriteKit
import ARKit

class ViewController: UIViewController, ARSKViewDelegate 

    @IBOutlet var sceneView: ARSKView!

    override func viewDidLoad() 
        super.viewDidLoad()
        // Set the view's delegate
        sceneView.delegate = self

        // Show statistics such as fps and node count
        sceneView.showsFPS = true
        sceneView.showsNodeCount = true

        // Load the SKScene from 'Scene.sks'
        if let scene = SKScene(fileNamed: "Scene") 
            sceneView.presentScene(scene)
        
    

    override func viewWillAppear(_ animated: Bool) 
        super.viewWillAppear(animated)

        // Create a session configuration
        let configuration = ARWorldTrackingSessionConfiguration()

        // Run the view's session
        sceneView.session.run(configuration)
    

    override func viewWillDisappear(_ animated: Bool) 
        super.viewWillDisappear(animated)

        // Pause the view's session
        sceneView.session.pause()
    

    override func didReceiveMemoryWarning() 
        super.didReceiveMemoryWarning()
        // Release any cached data, images, etc that aren't in use.
    

    // MARK: - ARSKViewDelegate

    func view(_ view: ARSKView, nodeFor anchor: ARAnchor) -> SKNode? 
        // Create and configure a node for the anchor added to the view's session.
        let labelNode = SKLabelNode(text: "????")
        labelNode.horizontalAlignmentMode = .center
        labelNode.verticalAlignmentMode = .center
        return labelNode;
    

    func session(_ session: ARSession, didFailWithError error: Error) 
        // Present an error message to the user

    

    func sessionWasInterrupted(_ session: ARSession) 
        // Inform the user that the session has been interrupted, for example, by presenting an overlay

    

    func sessionInterruptionEnded(_ session: ARSession) 
        // Reset tracking and/or remove existing anchors if consistent tracking is required

    

如果有必要，场景类：

import SpriteKit
import ARKit
class Scene: SKScene 

    override func didMove(to view: SKView) 
        // Setup your scene here
    

    override func update(_ currentTime: TimeInterval) 
        // Called before each frame is rendered
    

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) 
        guard let sceneView = self.view as? ARSKView else 
            return
        

        // Create anchor using the camera's current position
        if let currentFrame = sceneView.session.currentFrame 

            // Create a transform with a translation of 0.2 meters in front of the camera
            var translation = matrix_identity_float4x4
            translation.columns.3.z = -0.2
            let transform = simd_mul(currentFrame.camera.transform, translation)

            // Add a new anchor to the session
            let anchor = ARAnchor(transform: transform)
            sceneView.session.add(anchor: anchor)
        
    

【参考方案1】：

如果您只需要记录帧（如AVCaptureSession，而不是SCNNodes 的“真实” 3D 场景），只需在updateAtTime 的updateAtTime 委托函数中将它们作为ARFrame.capturedImage 获取：

func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) 
    createMovieWriterOnce(frame: session.currentFrame)
    appendFrameWithMetadaToMovie(frame: session.currentFrame)
   

我还没有找到从ARSession 获取帧大小的方法，所以MovieWriter 等待第一帧设置大小：

func createMovieWriterOnce(frame: ARFrame?) 
    if(frame == nil)  return 
    DispatchQueue.once(token: "SimplestMovieWriter.constructor") 
        movieWriter = SimplestMovieWriter(frameWidth: CVPixelBufferGetWidth(frame!.capturedImage), frameHeight: CVPixelBufferGetHeight(frame!.capturedImage))
    
 

接下来的每个CVPixelBuffer 都被馈送到MovieWriter：

func appendFrameWithMetadaToMovie(frame: ARFrame?) 
    if(!isVideoRecording || frame == nil)  return 
    let interestingPoints = frame?.rawFeaturePoints?.points
    movieWriter.appendBuffer(buffer: (frame?.capturedImage)!, withMetadata: interestingPoints)

MovieWriter 是带有AVAssetWriter、AVAssetWriterInput 和AVAssetWriterInputPixelBufferAdaptor 的自定义类。

您可以保存没有音频的视频，然后使用AVAssetExportSession 添加您想要的任何内容（音频、字幕、元数据）：

let composition = AVMutableComposition()
...
let trackVideo = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
let videoFileAsset = AVURLAsset(url: currentURL!, options: nil)
let videoFileAssetTrack = videoFileAsset.tracks(withMediaType: AVMediaTypeVideo)[0]

// add audio track here    

【讨论】：

非常感谢！这正是我所需要的，我不需要节点 :)