Как записать видео с веб-камеры в файлы MPEG или AVI с помощью настольного приложения C #

AVIWriter не обеспечивает видеокомпрессию, используйте FileWriter от AForge.Video.FFMPEG. Здесь вы можете выбрать все: размер, частоту кадров, кодек и битрейт, и если ваше видео было 600 МБ за 20 секунд, теперь оно будет 6 МБ за 20 секунд.

Ну вот:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using AForge.Video;
using AForge.Video.DirectShow;
using AForge.Video.FFMPEG;
using AForge.Video.VFW;

namespace WindowsFormsApplication12
{
    public partial class Form1 : Form
    {
        private FilterInfoCollection VideoCaptureDevices;

        private VideoCaptureDevice FinalVideo = null;
        private VideoCaptureDeviceForm captureDevice;
        private Bitmap video;
        //private AVIWriter AVIwriter = new AVIWriter();
        private VideoFileWriter FileWriter = new VideoFileWriter();
        private SaveFileDialog saveAvi;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {


            VideoCaptureDevices = new FilterInfoCollection(FilterCategory.VideoInputDevice);
            captureDevice = new VideoCaptureDeviceForm();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (captureDevice.ShowDialog(this) == DialogResult.OK)
            {

                VideoCaptureDevice videoSource = captureDevice.VideoDevice;
                FinalVideo = captureDevice.VideoDevice;
                FinalVideo.NewFrame += new NewFrameEventHandler(FinalVideo_NewFrame);
                FinalVideo.Start();
            }
        }
        void FinalVideo_NewFrame(object sender, NewFrameEventArgs eventArgs)
        {
            if (butStop.Text == "Stop Record")
            {
                video = (Bitmap)eventArgs.Frame.Clone();
                pictureBox1.Image = (Bitmap)eventArgs.Frame.Clone();
                //AVIwriter.Quality = 0;
                FileWriter.WriteVideoFrame(video);
                //AVIwriter.AddFrame(video);
            }
            else
            {
                video = (Bitmap)eventArgs.Frame.Clone();
                pictureBox1.Image = (Bitmap)eventArgs.Frame.Clone();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            saveAvi = new SaveFileDialog();
            saveAvi.Filter = "Avi Files (*.avi)|*.avi";
            if (saveAvi.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
                int h = captureDevice.VideoDevice.VideoResolution.FrameSize.Height;
                int w = captureDevice.VideoDevice.VideoResolution.FrameSize.Width;
                FileWriter.Open(saveAvi.FileName, w, h,25,VideoCodec.Default,5000000);
                FileWriter.WriteVideoFrame(video);

                //AVIwriter.Open(saveAvi.FileName, w, h);
                butStop.Text = "Stop Record";
                //FinalVideo = captureDevice.VideoDevice;
                //FinalVideo.NewFrame += new NewFrameEventHandler(FinalVideo_NewFrame);
                //FinalVideo.Start();
            }
        }

        private void butStop_Click(object sender, EventArgs e)
        {
            if (butStop.Text == "Stop Record")
            {
                butStop.Text = "Stop";
                if (FinalVideo == null)
                { return; }
                if (FinalVideo.IsRunning)
                {
                    //this.FinalVideo.Stop();
                    FileWriter.Close();
                    //this.AVIwriter.Close();
                    pictureBox1.Image = null;
                }
            }
            else
            {
                this.FinalVideo.Stop();
                FileWriter.Close();
                //this.AVIwriter.Close();
                pictureBox1.Image = null;
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            pictureBox1.Image.Save("IMG" + DateTime.Now.ToString("hhmmss") + ".jpg");
        }

        private void button4_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (FinalVideo == null)
            { return; }
            if (FinalVideo.IsRunning)
            {
                this.FinalVideo.Stop();
                FileWriter.Close();
                //this.AVIwriter.Close();
            }
        }


    }
}