与.NET程序中的ffmpeg交互？

Question

我正在尝试使用ffmepg创建用于媒体文件转换的.NET包装器,这是我尝试过的:

static void Main(string[] args)
{
  if (File.Exists("sample.mp3")) File.Delete("sample.mp3");

  string result;

  using (Process p = new Process())
  {
    p.StartInfo.FileName = "ffmpeg";
    p.StartInfo.Arguments = "-i sample.wma sample.mp3";

    p.StartInfo.UseShellExecute = false;
    p.StartInfo.RedirectStandardOutput = true;

    p.Start();

    //result is assigned with an empty string!
    result = p.StandardOutput.ReadToEnd();

    p.WaitForExit();
  }
}

实际发生的是ffmpeg程序的内容打印到Console应用程序,但result变量是一个空字符串.我希望以交互方式控制转换进度,因此用户甚至不必知道我正在使用ffmpeg,但他仍然知道转换进度的详细信息以及应用程序所需的百分比等.

基本上我也很满意只有P/Invoke到转换函数的.NET包装器(我对整个外部库不感兴趣,除非我可以从中提取PI函数).

有ffmpeg和.NET经验的人吗？

更新 请查看我的进一步问题,如何将输入写入正在运行的ffmpeg进程.

Answer 1

这是答案:

static void Main()
{
  ExecuteAsync();
  Console.WriteLine("Executing Async");
  Console.Read();
}

static Process process = null;
static void ExecuteAsync()
{
  if (File.Exists("sample.mp3"))
    try
    {
      File.Delete("sample.mp3");
    }
    catch
    {
      return;
    }

  try
  {
    process = new Process();
    ProcessStartInfo info = new ProcessStartInfo("ffmpeg.exe",
        "-i sample.wma sample.mp3");

    info.CreateNoWindow = false;
    info.UseShellExecute = false;
    info.RedirectStandardError = true;
    info.RedirectStandardOutput = true;

    process.StartInfo = info;

    process.EnableRaisingEvents = true;
    process.ErrorDataReceived +=
        new DataReceivedEventHandler(process_ErrorDataReceived);
    process.OutputDataReceived +=
        new DataReceivedEventHandler(process_OutputDataReceived);
    process.Exited += new EventHandler(process_Exited);

    process.Start();

    process.BeginOutputReadLine();
    process.BeginErrorReadLine();
  }
  catch
  {
    if (process != null) process.Dispose();
  }
}

static int lineCount = 0;
static void process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
{
  Console.WriteLine("Input line: {0} ({1:m:s:fff})", lineCount++,
      DateTime.Now);
  Console.WriteLine(e.Data);
  Console.WriteLine();
}

static void process_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
  Console.WriteLine("Output Data Received.");
}

static void process_Exited(object sender, EventArgs e)
{
  process.Dispose();
  Console.WriteLine("Bye bye!");
}