Using AFORGE to record the videos in c#

Question

i've try the following way to record the video from the Webcam by 25 Frame-rate per sec for 10sec but when i get the out put video it is of 2sec and the frames are played to fast as compare to the video stream.

The code is as follows.

    using System;
using System.Drawing;
using System.Windows.Forms;
using AForge.Video;
using AForge.Video.DirectShow;
using System.Threading;
using AForge.Video.FFMPEG;

namespace AforgeTutorial
{
    public partial class Form1 : Form
    {
        private FilterInfoCollection ListOfCams;
        private VideoCaptureDevice SelectedCam; //From where we will take image
        System.Timers.Timer tim;

        Thread t;
        bool isNewFrame = false;
        VideoFileWriter writer;

        public Form1()
        {
            InitializeComponent();
            tim = new System.Timers.Timer(10000);
            tim.Elapsed += new System.Timers.ElapsedEventHandler(tim_Elapsed);
            t = new Thread(saveVideo);
        }

        void tim_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            if (isRecord)
            {
                writer.Close();
                isRecord = false;
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            ListOfCams = new FilterInfoCollection(FilterCategory.VideoInputDevice);

            if (ListOfCams.Count == 0)
                return;

            comboBox1.Items.Clear();
            foreach (FilterInfo Cam in ListOfCams)
            {
                comboBox1.Items.Add(Cam.Name);
            }
        }

        private void StopCamera()
        {
            SelectedCam.SignalToStop();
            SelectedCam.Stop();
        }

        bool isRecord = false;

        private void Start_Click(object sender, EventArgs e)
        {
            if (comboBox1.Text == string.Empty)
                return;

            SelectedCam = new VideoCaptureDevice(ListOfCams[comboBox1.SelectedIndex].MonikerString);

            SelectedCam.NewFrame += new NewFrameEventHandler(SelectedCam_NewFrame);
            SelectedCam.Start();
        }

        Bitmap image;
        void SelectedCam_NewFrame(object sender, NewFrameEventArgs eventArgs)
        {
            image = (Bitmap)eventArgs.Frame.Clone();
            isNewFrame = true;
            pictureBox1.Image = (Bitmap)eventArgs.Frame.Clone();            
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            StopCamera();
        }

        private void Stop_Click(object sender, EventArgs e)
        {
            StopCamera();
        }

        private void btnRecord_Click(object sender, EventArgs e)
        {
            tim.Start();

            if (!isRecord)
            {
                writer = new VideoFileWriter();
                writer.Open(@"C:/code-bude_test_video.mp4", 640, 480, 25, VideoCodec.MPEG4,10000);
            }

            isRecord = !isRecord;
            if (isRecord)
                t.Start();
        }

        void saveVideo()
        {
            while (isRecord)
            {
                if (isNewFrame)
                {
                    writer.WriteVideoFrame(image);
                    isNewFrame = false;
                }
            }
        }
    }
}

Answer 1

You have multi-threading issues in your code. You can't write to shared variables like that and expect it to synchronize.

You have three threads: user interface, streaming and saving. (SelectedCam_NewFrame runs in the AForge streaming thread). Make a list of all variables that are accessed in at least two threads (isRecord, isNewFrame, etc) and add proper synchronization.

You can check this very good reference on threading in C#.

Note that even with synchronization, you may miss frames if your writer thread is busy while several images arrive. What you might want to do is collect the frames produced by the camera in a queue and consume that queue in the writer thread. Check the producer/consumer patterns.