使用c# avformat_open运行ffmpeg失败

using System;
using FFmpeg.AutoGen;

namespace FFMpegExample
{
    class Program
    {
        static unsafe void Main(string[] args)
        {
            avformat.av_register_all();

            AVFormatContext* formatContext = null;
            int result = avformat_open_input(&formatContext, "input.mp4", null, null);
            if (result != 0)
            {
                byte* buffer = stackalloc byte[AV_ERROR_MAX_STRING_SIZE];
                av_strerror(result, buffer, AV_ERROR_MAX_STRING_SIZE);
                Console.WriteLine("Failed to open input file: {0}", new string(buffer));
                return;
            }

            // 继续处理媒体文件...

            avformat_close_input(&formatContext);
        }
    }
}