I'm trying to receive frame data and render to MTKView in 60fps.
My MTKView almost the same as PreviewView.swift in Reference about SwiftUI using MTKView

ContentView:

struct ContentView: View {

    @State var navigationPath = NavigationPath()
    @StateObject var ndi_c = NDI.shared

    init(){
        UIApplication.shared.isIdleTimerDisabled = true
    }
    
    var body: some View {
        
        NavigationStack (path: $navigationPath){
        #if !(targetEnvironment(simulator))
            ZStack{
//This is the MTKView, and code is almost same in https://github.com/frankschlegel/core-image-by-example/blob/main/Shared/PreviewView.swift

                NDIView(imagePublisher: self.ndi_c.$NDI_Frame.eraseToAnyPublisher())
                    .onAppear(){
                        ndi_c.StartRecv()
                        ARData.shared.HideARView = NDIView_Top
                    }

//Doing something...

                }.navigationDestination(for: viewDest.self) { target in
                    switch target {
                    case .MainView:
                        ContentView()
                    case .SettingsView:
                        Settings()
                    }
                }
            }

        #endif
        }
    }
}

This is code about ndi_c.StartRecv():

class NDI: ObservableObject{
    
    @Published var NDI_Frame: CIImage?
    let NDI_Queue = DispatchQueue(label: "NDI_recv")
    static var shared = NDI()
    var ndi_t: NDIWrapper?
    var Connected: Bool = false
    
    init(){
        ndi_t = NDIWrapper()
    }

    \\Do Something...
    
    func PrepareFrame() -> CVPixelBuffer?{

        var Buf: CVPixelBuffer?
        
        if let data = self.ndi_t?.getRecvBuf(){
            Buf = data.takeRetainedValue()
        }
        return Buf
    }
    
    func StartRecv(){

        Connected = ndi_t!.startRecv(SelectedSource ?? "")

        NDI_Queue.async {
            while(self.Connected){
                if let buf = self.PrepareFrame(){
                    let ciImage = CIImage(cvPixelBuffer: buf)
                    DispatchQueue.main.async {
                        self.NDI_Frame = ciImage
                    }
                }
            }
        }

    }
}

I use PrepareFrame() to grab and create CVPixelBuffer from uint8_t*, After that, I convert it to CIImage.
Finally I use @Published to update NDI_Frame and refresh to MTKView on main thread.

Unfortunately the view is laggy, Framerate is very unstable.
Creating CVPixelBuffer in my code only cost about 5% CPU usage .
But Main thread is overloading when I publish the data.

Sorry, I'm very new on Swift.
Please tell me where am I doing wrong.
Appreciate it.

CodePudding user response：

Don't you think there is an infinite loop going on in the code above: while(self.Connected)? I would recommend using a timer or some other form of scheduling to limit the amount of times the loop is run or rethink the code totally.

CodePudding user response：

SwiftUI view data state updates aren't designed to run at 60fps, maybe 1 per second max, so I think you should implement your custom rendering at a lower level in the system.