C#从wmv文件中获取帧

using System;
using System.IO;
using System.Windows.Forms;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using Microsoft.WindowsMediaFoundation;

namespace WMVPlayer
{
    public partial class Form1 : Form
    {
        private const int MF_SOURCE_READER_FIRST_VIDEO_STREAM = 0xFFFFFFFE;
        private const int MF_SOURCE_READER_ALL_STREAMS = 0xFFFFFFFF;

        private IMFSourceReader sourceReader;
        private IMFMediaType mediaType;
        private IMFSample sample;
        private Bitmap bitmap;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.Filter = "WMV files (*.wmv)|*.wmv";
            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = openFileDialog.FileName;
                InitializePlayer(openFileDialog.FileName);
            }
        }

        private void InitializePlayer(string fileName)
        {
            // Create the source reader
            sourceReader = (IMFSourceReader)new MFSourceReader();

            // Create the media type
            mediaType = (IMFMediaType)new MFVideoMediaType();

            // Set the video format
            mediaType.SetGUID(MFAttributesClsid.MF_MT_MAJOR_TYPE, MFMediaType.MFMediaType_Video);
            mediaType.SetGUID(MFAttributesClsid.MF_MT_SUBTYPE, MFMediaType.MFVideoFormat_RGB32);

            // Create the sample
            sample = (IMFSample)new MFSample();

            // Create the bitmap
            bitmap = new Bitmap(pictureBox1.Width, pictureBox1.Height, PixelFormat.Format32bppArgb);

            // Initialize the source reader
            sourceReader.SetStreamSelection(MF_SOURCE_READER_ALL_STREAMS, false);
            sourceReader.SetStreamSelection(MF_SOURCE_READER_FIRST_VIDEO_STREAM, true);
            sourceReader.SetCurrentMediaType(MF_SOURCE_READER_FIRST_VIDEO_STREAM, IntPtr.Zero, mediaType);

            // Read the first frame
            ReadFrame();
        }

        private void ReadFrame()
        {
            int hr = sourceReader.ReadSample(MF_SOURCE_READER_FIRST_VIDEO_STREAM, 0, IntPtr.Zero, 0, IntPtr.Zero, IntPtr.Zero);
            if (hr == 0)
            {
                // Get the sample from the source reader
                sourceReader.GetSample(MF_SOURCE_READER_FIRST_VIDEO_STREAM, sample);

                // Get the buffer from the sample
                IMFMediaBuffer mediaBuffer = (IMFMediaBuffer)sample;

                // Lock the buffer
                mediaBuffer.Lock(out IntPtr buffer, out int maxLength, out int currentLength);

                // Copy the buffer to the bitmap
                Marshal.Copy(buffer, bitmap.Scan0, 0, currentLength);

                // Unlock the buffer
                mediaBuffer.Unlock();

                // Draw the bitmap
                pictureBox1.Image = bitmap;
            }
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            ReadFrame();
        }
    }
}