AForge.NET：未触发 NewFrameEventHandler 参数方法

Question

I am attempting to write a Windows Console program that is capable of acquiring imagery from a webcam or a virtual webcam, extracting a bitmap frame from the video source and saving the frame to the filesystem as a bitmap file.

Currently I use a program called OBS Studio to emulate a video source with the "Virtual Camera" option.

Here is the code:

using System;
using AForge.Video.DirectShow;
using AForge.Video;
using System.Drawing;

namespace webcamc
{
    class Program
    {
        FilterInfoCollection filterInfoCollection;
        VideoCaptureDevice videoCaptureDevice;
        Bitmap bitmap;

        static void Main(string[] args)
        {
            var program = new Program();
            program._init();
        }

        void _handleNewFrameEvent(object sender, NewFrameEventArgs eventArgs)
        {
            bitmap = new Bitmap(eventArgs.Frame);
        }

        void _init()
        {
            filterInfoCollection = new FilterInfoCollection(FilterCategory.VideoInputDevice);
            videoCaptureDevice = new VideoCaptureDevice(filterInfoCollection[0].MonikerString);
            videoCaptureDevice.Start();
            videoCaptureDevice.NewFrame += new NewFrameEventHandler(_handleNewFrameEvent);
           
            string ActiveDir = AppDomain.CurrentDomain.BaseDirectory;
            string filepath = System.IO.Path.Combine(ActiveDir, @"C://Pic");

            string fileName = System.IO.Path.Combine(filepath, @"name.bmp");
            bool fileNotExists = !System.IO.File.Exists(fileName);
            if (fileNotExists)
            {
               bitmap.Save(fileName);
            }

        }

    }
}

Unfortunately, I am unable to understand why the _handleNewFrameEvent method that I pass to the NewFrameEventHandler is not triggered; i have inspected the code with a debugger and the breakpoint is not hit. I am quite sure that the device list and the device moniker is acquired correctly. However I doubt very much the videoCaptureDevice instance. I am not sure but it looks like it is not correctly instantiated since all the pertaining values appear to be 0.

Here is an image of the debugger showing the ill-instantiated video capture device

Could anyone please point me in the right direction?

Thank you.

Answer 1

I would first move videoCaptureDevice.Start(); below videoCaptureDevice.NewFrame += new NewFrameEventHandler(_handleNewFrameEvent); as you only want to start running the camera feed once you can receive the new frames (but I am not confident that this will solve your problem).

Maybe there is an error being thrown by the starting of the webcam so adding a vDevIn.VideoSourceError += new VideoSourceErrorEventHandler(errorHandler) and see if there is any error thrown using function below:

    private void errorHandler(object sender, VideoSourceErrorEventArgs eventArgs)
{
    Console.WriteLine("Video feed source error: " + eventArgs.Description);
}