Swift IOS activeVideoMinFrameDuration 不起作用

Question

我有一个代码可以从应用中捕获预览图像以进行图像处理。为此，我需要控制预览的帧速率，但是设置帧速率的代码对预览流没有影响。这里是代码

import UIKit
import AVFoundation
import Starscream
import SwiftyJSON



class ViewController: UIViewController, WebSocketDelegate {
    
    
    var captureSession: AVCaptureSession?
    
    var rearCamera: AVCaptureDevice?
    var rearCameraInput: AVCaptureDeviceInput?
    var videoPreviewOutput: AVCaptureVideoDataOutput?
    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    
    var socket: WebSocket!
    let server = WebSocketServer()
    var isConnected = false
    var json:JSON = JSON()
    var json1:JSON = JSON()
    var jsonAction:JSON = JSON()
    
    var captureDevice: AVCaptureDevice?
    
   
    var hr_raw1 = [Int]()
    
    var time_raw1 = [Int]()
    var bpm_list = [Double]()
    
    var time_list = [Int]()
    var frames1 = [Int]()
    
    
    var start_time:Int = -1
    var current_time:Int = 0
    var last_time:Int = 0
    
    var init_stamp:Int = -1
    var current_stamp:Int = 0
    var last_stamp:Int = 0
    
    @IBOutlet var bpmText: UILabel!
    
    @IBOutlet var fpsText: UILabel!
    
   
    override func viewDidLoad() {
        super.viewDidLoad()
        
        var request = URLRequest(url: URL(string: "wss://jznm58xz5i.execute-api.ap-south-1.amazonaws.com/production")!)
        request.timeoutInterval = 10
        socket = WebSocket(request: request)
        socket.delegate = self
        socket.connect()
        
        self.captureSession = AVCaptureSession()
        
       self.captureSession?.sessionPreset = .inputPriority
        
        let session = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .back)
        
        self.rearCamera = session.devices.first
        
        
        if let rearCamera = self.rearCamera {
            
            // we try to create the input from the found camera
            self.rearCameraInput = try? AVCaptureDeviceInput(device: rearCamera)
            
            if let rearCameraInput = rearCameraInput {
                
                // always make sure the AVCaptureSession can accept the selected input
                if ((captureSession?.canAddInput(rearCameraInput)) != nil) {
                    
                    // add the input to the current session
                    captureSession?.addInput(rearCameraInput)
                }
            }
        }
        do{
            try rearCamera?.lockForConfiguration()
            try? rearCamera?.setTorchModeOn(level: 1.0)
            rearCamera?.activeVideoMinFrameDuration = CMTimeMake(value: 1, timescale: 30)
            rearCamera?.activeVideoMaxFrameDuration = CMTimeMake(value: 1, timescale: 30)
            rearCamera?.unlockForConfiguration()
        }catch{
            
            
        }
        
        if let captureSession = captureSession {
            // create the preview layer with the configuration you want
            self.videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
            self.videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
            self.videoPreviewLayer?.connection?.videoOrientation = .portrait
            
            // then add the layer to your current view
            view.layer.insertSublayer(self.videoPreviewLayer!, at: 0)
            self.videoPreviewLayer?.frame = view.frame
        }
        
        self.videoPreviewOutput = AVCaptureVideoDataOutput()
        self.videoPreviewOutput!.setSampleBufferDelegate(self, queue: DispatchQueue(label: "sample buffer"))
        
        // always make sure the AVCaptureSession can accept the selected output
        if ((captureSession?.canAddOutput(self.videoPreviewOutput!)) != nil) {
            
            // add the output to the current session
            captureSession?.addOutput(self.videoPreviewOutput!)
        }
        
        
        self.captureSession?.commitConfiguration()
      
        self.captureSession?.startRunning()
        
        
    }

手电筒也会在会话开始后立即关闭，我不明白为什么会这样。

Answer 1

检查它是否支持所需的FPS：

extension AVCaptureDevice {
    func configureFPS(_ inputFrameRate: Int) {

        var isFPSSupported = false

        do {

             let supportedFrameRange = activeFormat.videoSupportedFrameRateRanges
                for range in supportedFrameRange {
                    if (range.maxFrameRate >= Double(inputFrameRate) && range.minFrameRate <= Double(inputFrameRate)) {
                        isFPSSupported = true
                        break
                    }
                }

            if isFPSSupported {
                try lockForConfiguration()
                activeVideoMaxFrameDuration = CMTimeMake(value: 1, timescale: Int32(inputFrameRate))
                activeVideoMinFrameDuration = CMTimeMake(value: 1, timescale: Int32(inputFrameRate))
                unlockForConfiguration()
            }

        } catch {
            print("lockForConfiguration error: \(error.localizedDescription)")
        }
    }
}