如何以 240fps 调用 captureOutput？

如何解决如何以 240fps 调用 captureOutput？

我想以高帧率保存图像。 IO 很贵，不是准确的 240fps。但可能超过 120fps。

我所做的是在 viewDidLoad 中设置 capturedivece， 并在 captureOutput 中记录时间戳并查看费率。

但我注意到 captureOutput 总是 30fps。 你能告诉我我做错了什么吗？

感谢您的时间和回答！

这是我的代码和结果：

//
//  ViewController.swift
//  CustomCamera
//
//  Created by chunibyo on 2021/3/8.
//

import UIKit
import AVFoundation
import Vision
import VideoToolBox

class ViewController: UIViewController,AVCaptureVideoDataOutputSampleBufferDelegate {
    
    @IBOutlet weak var captureButton: UIButton!
    let sessionQueue = dispatchQueue(label: "Session Queue")
    var status = false
    private var MyCaptureDevice: AVCaptureDevice?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        captureButton.layer.cornerRadius = captureButton.frame.width / 2
        captureButton.layer.masksToBounds = true
        captureButton.layer.zPosition = 10
        
        guard let captureDevice = AVCaptureDevice.default(.builtInDualCamera,for: .video,position: .back) else {return}

        guard let input = try? AVCaptureDeviceInput(device: captureDevice) else {return}
        
        // 1
        for vFormat in captureDevice.formats {
            // 2
            let ranges = vFormat.videoSupportedFrameRateranges as [AVFrameRaterange]
            let frameRates = ranges[0]
            // 3
            if frameRates.maxFrameRate == 240 {
                // 4
                try? captureDevice.lockForConfiguration()
                captureDevice.activeFormat = vFormat as AVCaptureDevice.Format
                captureDevice.activeVideoMinFrameDuration = CMTimeMake(value: 1,timescale: Int32(240))
                captureDevice.activeVideoMaxFrameDuration = CMTimeMake(value: 1,timescale: Int32(240))
                captureDevice.videoZoomFactor = captureDevice.minAvailableVideoZoomFactor
                captureDevice.unlockForConfiguration()
            }
        }
        
        let captureSession = AVCaptureSession();
        // captureSession.sessionPreset = .photo
        captureSession.addInput(input)
        captureSession.startRunning();
        
        let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        view.layer.addSublayer(previewLayer)
        previewLayer.frame = view.frame
        
        let dataOutput = AVCaptureVideoDataOutput()
        dataOutput.setSampleBufferDelegate(self,queue: dispatchQueue(label: "videoQueue"))
        dataOutput.alwaysdiscardsLateVideoFrames = true;
        captureSession.addOutput(dataOutput)
        
        print(captureDevice.minAvailableVideoZoomFactor)
        print(captureDevice.maxAvailableVideoZoomFactor)
        
        MyCaptureDevice = captureDevice
    }

    func captureOutput(_ output: AVCaptureOutput,didOutput sampleBuffer: CMSampleBuffer,from connection: AVCaptureConnection) {
        print(CMTimeGetSeconds(CMSampleBufferGetPresentationTimeStamp(sampleBuffer)))
//        if !status { return }
//        guard let pixelBuffer: CVPixelBuffer = CMSampleBufferGetimageBuffer(sampleBuffer) else { return }
//        guard let uiImage = UIImage(pixelBuffer: pixelBuffer) else { return }
//
//        sessionQueue.async {
//            guard let captureDevice = self.MyCaptureDevice else { return }
//            if captureDevice.videoZoomFactor >= (captureDevice.maxAvailableVideoZoomFactor - 0.2) { return }
//            UIImageWritetoSavedPhotosAlbum(uiImage,nil,nil)
//            try? captureDevice.lockForConfiguration()
//            captureDevice.videoZoomFactor += 0.1
//            captureDevice.unlockForConfiguration()
//        }
    }

    @IBAction func captureControl(_ sender: UIButton) {
        dispatchQueue.main.async {
            if self.status {
                self.captureButton.backgroundColor = .white
                print("stop")
                self.status = !self.status
            }
            else {
                self.captureButton.backgroundColor = .red
                print("recording...")
                self.status = !self.status
            }
            
        }
    }
}

extension UIImage {
    public convenience init?(pixelBuffer: CVPixelBuffer) {
        var cgImage: CGImage?
        VTCreateCGImageFromCVPixelBuffer(pixelBuffer,options: nil,imageOut: &cgImage)
        guard let _cgImage = cgImage else { return nil }
        self.init(cgImage: _cgImage)
    }
}

console log（stackoverflow 不允许我发布图片，抱歉）

解决方法

CacheConfiguration 只有日志是 240fps。

captureOutput 拍照到相册大约是 70~100fps。

此代码可以获得 240fps 的日志。

captureOutput