截取视频文件第一桢的图片和转换视频格式文件为flv

public class CatchFlv
{
    public CatchFlv()
    {
    }
    /**/
    /// <summary>
    /// @从视频文件截图,生成在视频文件所在文件夹
    /// 支持文件格式:asf,avi,mpg,flv,3gp,mov,wmv
    /// 在Web.Config 中需要两个前置配置项:
    /// 1.ffmpeg.exe文件的路径
    /// <add key="ffmpeg" value="\thread\ffmpeg\ffmpeg.exe" />
    /// 2.截图的尺寸大小
    /// <add key="CatchFlvImgSize" value="140x110" />
    /// 3.视频处理程序ffmpeg.exe
    /// </summary>
    /// <param name="vFileName">视频文件绝对或相对地址,如:(..)/Web/FlvFile/User1/001.avi</param>
    /// <returns>成功:返回图片绝对/相对地址; 失败:返回空字符串</returns>
    public static string CatchImg(string vFileName)
    {
        try
        {
            string ffmpeg = System.Configuration.ConfigurationSettings.AppSettings["ffmpeg"];
            ffmpeg = HttpContext.Current.Server.MapPath(ffmpeg);

            if ((!System.IO.File.Exists(ffmpeg)) || (!System.IO.File.Exists(System.Web.HttpContext.Current.Server.MapPath(vFileName))))
            {
                return "";
            }

            //获得图片相对路径/最后存储到数据库的路径,如:/Web/FlvFile/User1/00001.jpg
            string flv_img = System.IO.Path.ChangeExtension(vFileName, ".jpg");

            //图片绝对路径,如:D:\Video\Web\FlvFile\User1\0001.jpg
            string flv_img_p = HttpContext.Current.Server.MapPath(flv_img);

            //截图的尺寸大小,配置在Web.Config中,如:<add key="CatchFlvImgSize" value="140x110" />
            string FlvImgSize = System.Configuration.ConfigurationSettings.AppSettings["CatchFlvImgSize"];

            System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo(ffmpeg);
            startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Normal;

            //此处组合成ffmpeg.exe文件需要的参数即可,此处命令在ffmpeg 0.4.9调试通过
            startInfo.Arguments = " -i " + System.Web.HttpContext.Current.Server.MapPath(vFileName) + " -y -f image2 -t 0.001 -s " + FlvImgSize + " " + flv_img_p;
            try
            {
                System.Diagnostics.Process.Start(startInfo);
            }
            catch
            {
                return "";
            }
            System.Threading.Thread.Sleep(4000);
            /**/
            ///注意:图片截取成功后,数据由内存缓存写到磁盘需要时间较长,大概在3,4秒甚至更长;
            if (System.IO.File.Exists(flv_img_p))
            {
                return flv_img;
            }
            return "";
        }
        catch
        {
            return "";
        }

    }

    /**/
    /// <summary>
    /// @视频文件格式转换,生成在视频文件所在文件夹
    /// 支持文件格式:asf,avi,mpg,flv,3gp,mov,wmv
    /// 在Web.Config 中需要两个前置配置项:
    /// 1.ffmpeg.exe文件的路径
    /// <add key="ffmpeg" value="\thread\ffmpeg\ffmpeg.exe" />
    /// 2.截图的尺寸大小
    /// <add key="CatchFlvSize" value="240x180" />
    /// 3.视频处理程序ffmpeg.exe
    /// </summary>
    /// <param name="vFileName">视频文件绝对或相对地址,如:(..)/Web/FlvFile/User1/001.avi</param>
    /// <returns>成功:返回flv文件绝对/相对地址; 失败:返回空字符串</returns>
    public static string ChangeMediaFormat(string vFileName)
    {
        try
        {
            string ffmpeg = System.Configuration.ConfigurationSettings.AppSettings["ffmpeg"];
            string wks_url = System.Configuration.ConfigurationSettings.AppSettings["wks_local"];
            ffmpeg = wks_url + ffmpeg;
            if ((!System.IO.File.Exists(ffmpeg)) || (!System.IO.File.Exists(wks_url + vFileName)))
            {
                return "";
            }

            string flv_fot = System.IO.Path.ChangeExtension(vFileName, ".flv");
            string flv_fot_p = wks_url + flv_fot;

            //尺寸大小,配置在Web.Config中,如:<add key="CatchFlvSize" value="240x180" />
            string FlvImgSize = System.Configuration.ConfigurationSettings.AppSettings["CatchFlvSize"];

            System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo(ffmpeg);
            startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Normal;

            //此处组合成ffmpeg.exe文件需要的参数即可,此处命令在ffmpeg 0.4.9调试通过
            startInfo.Arguments = " -i " + wks_url + vFileName + " -ab 56 -ar 22050 -b 500 -r 15 -s  " + FlvImgSize + " " + flv_fot_p;

            try
            {
                System.Diagnostics.Process.Start(startInfo);
            }
            catch
            {
                return "";
            }

            /**/
            ///注意:文件格式转换成功后,数据由内存缓存写到磁盘需要时间较长,大概在3,4秒甚至更长;
            System.Threading.Thread.Sleep(6000);
            if (System.IO.File.Exists(flv_fot_p))
            {
                WKS.Common.ImagesSet.DeleteOleImg(wks_url + vFileName);
                return flv_fot;
            }

            return "";
        }
        catch
        {
            return "";
        }
    }
}

但是，这种方法不知道ffmpeg什么时候生成结果，生成什么样的结果，因此也存在一定局限性.