如何捕获FFMPEG输出 [英] How to catch FFMPEG Output

问题描述

大家好。

我试过下一行：

过程p =  new  Process（）; 
 p.StartInfo.UseShellExecute =  false ; 
 p.StartInfo.RedirectStandardOutput =  true ; 
 p.StartInfo.CreateNoWindow =  true ; 
 p.StartInfo.FileName =   ffmpeg; 
  p.StartInfo.Arguments =   -h;  
p = Process.Start（p.StartInfo）; 
  this  .textBox1.Text = p.StandardOutput.ReadToEnd（）; 
  this  .textBox1.Update（）; 
 p.WaitForExit（）; 

在这种情况下，一切看起来都很好，TextBox的输出为ffmpeg.exe。

但是在实际工作的情况下：

 p.StartInfo.Arguments =   -i input.avi -y output.ts; 

我只能看到空文本框convertion已经完成并且output.ts已经创建。



提前谢谢。

解决方案

文章中发现了最好和最短的解决方案

'由Jonathan Lathigee发布的ffmpeg'视频转码YouTube风格。

使用ffmpeg 视频转码YouTube风格

他写道：

另一个问题是从FFMPEG捕获输出以获取所有文件的元数据。我创建了一个新进程和streamReader，从进程中捕获StandardOutput。没有。原来在FFMPEG中没有特定命令从视频文件中读取元数据，而当调用FFMPEG时没有指定输出文件，此信息作为StandardError流出现。一旦切换从捕获StandardOutput到StandardError，我没有遇到任何问题。



这对我来说是关键因素。当我试图捕获ffmpeg的StandardOutput而不是捕获StandardError时。所以我在TextBox中获得了所有必要的行。最后我使用了更适合我的目的的异步阅读。这是代码。

 尝试 
 {
处理p = 此 .process1; 
 字符串 input =   -i +  this  .listBox2.Text;  //   / c ffmpeg.exe //用于通过cmd.exe启动ffmpeg  
  String  size =   -s + 此 .comboBox1.Text; 
 字符串 codec =   -vcodec + 此 .comboBox2.Text; 
 字符串编码器=   -vtag + 此 .comboBox3.Text; 
 字符串 quality =   -qscale + 此 .comboBox4.Text; 
 字符串 videobr =   -b：v  + 此 .comboBox4.Text +   K; 
 字符串 audiobr =   -ab +  this  .comboBox5.Text +   k ; 
 字符串 output =   -y +  this  .textBox2.Text; 
 字符串 report =   2> \  + 此 .textBox2.Text +   .log\;  //  用于通过cmd.exe启动ffmpeg并将输出放入文件 
 字符串 s = input + size + codec + encoder + videobr + audiobr + output;  //   + report;  
 字符串 sa =   -h;  //  来自ffmpeg的帮助 
 p.StartInfo.Arguments = s; 
 p.Start（）; 
 
 p.BeginOutputReadLine（）; 
 p.BeginErrorReadLine（）; 
 MessageBox.Show（ 等待进程退出....）; 
  //   p.WaitForExit（）;  
  if （p.HasExited）{p.CancelErrorRead（）; p.CancelOutputRead（）; p.Close（）; MessageBox.Show（  Closed）; } 
} 
  catch （Exception ex）
 {
 MessageBox.Show（  1. \ n + ex.Message）; 
} 

关注ErrorDataReceived处理程序。

  private   void  process1_ErrorDataReceived（ object  sender，DataReceivedEventArgs e）
 {
  this  .textBox1.Text + = e.Data; 
  this  .textBox1.Update（）; 
  //   MessageBox.Show（4.Error\\\
+ e.Data）;  
} 

你可以找到一些额外的行：MessageBoxes等它们只是用于调试。

非常感谢Jonathan Lathigee和他的5星。

如果我的经验对你有用，我很高兴。

祝福。

Hello everybody.
I've tried next lines:

Process p = new Process();
p.StartInfo.UseShellExecute = false;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.CreateNoWindow = true;
p.StartInfo.FileName = "ffmpeg";
p.StartInfo.Arguments = " -h ";
p = Process.Start(p.StartInfo);
this.textBox1.Text = p.StandardOutput.ReadToEnd();
this.textBox1.Update();
p.WaitForExit();

In this case everything looks fine and TextBox have got a output of ffmpeg.exe.
But in case of real job:

p.StartInfo.Arguments = " -i input.avi -y output.ts ";

I can see just empty TextBox although convertion has been completed and output.ts has been created.

Thanks in advance.

解决方案

The best and the shortest solution was found in the article
' Video Transcoding "YouTube-Style" with ffmpeg ' posted by Jonathan Lathigee.
Video Transcoding "YouTube-Style" with ffmpeg
He writes:
"Another problem came in the capturing of output from FFMPEG to get all of the file's metadata. I created a new process and streamReader, and captured the StandardOutput from the process. Nothing. Turns out that there is no specific command in FFMPEG to read metadata from a video file, instead this info comes out as a StandardError stream when FFMPEG is called with no output file specified. Once I switched from capturing the StandardOutput to StandardError, I had no problems."

And that was key factor for me. As I tried to catch StandardOutput of ffmpeg instead of catching StandardError. So I got all necessary lines into my TextBox. Finally I used asynchronous reading that was more suitable for my purpose. Here is the code.

try
            {
                Process p = this.process1;
                String input = " -i " + this.listBox2.Text; //  /c ffmpeg.exe // for launching ffmpeg via cmd.exe
                String size = " -s " + this.comboBox1.Text;
                String codec = " -vcodec " + this.comboBox2.Text;
                String encoder = " -vtag " + this.comboBox3.Text;
                String quality = " -qscale " + this.comboBox4.Text;
                String videobr = " -b:v " + this.comboBox4.Text + "k";
                String audiobr = " -ab " + this.comboBox5.Text + "k";
                String output = " -y " + this.textBox2.Text;
                String report = " 2> \"" + this.textBox2.Text + ".log\""; // for launching ffmpeg via cmd.exe and putting output into file
                String s = input + size + codec + encoder + videobr + audiobr + output;// +report;
                String sa = " -h ";// help from ffmpeg
                p.StartInfo.Arguments = s;
                p.Start();

                p.BeginOutputReadLine();
                p.BeginErrorReadLine();
                MessageBox.Show("Waiting for the process to exit....");
                //p.WaitForExit();
                if (p.HasExited) { p.CancelErrorRead(); p.CancelOutputRead(); p.Close(); MessageBox.Show("Closed"); }
            }
            catch (Exception ex)
            {
                MessageBox.Show("1.\n"+ex.Message);
            }

Following ErrorDataReceived handler.

private void process1_ErrorDataReceived(object sender, DataReceivedEventArgs e)
        {
            this.textBox1.Text += e.Data;
            this.textBox1.Update();
            //MessageBox.Show("4.Error\n" + e.Data);
        }

You can find some extra lines: MessageBoxes etc. they are just for debugging.
So Great Thanks to Jonathan Lathigee and 5 stars for him.
I'm glad if my experience is usefull for you.
Best wishes.

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