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• Handling "NullReferenceException" when executing "ffmpeg.exe" process in C# [duplicate]

  1er juillet 2023, par FrostDream

  I'm trying to execute the "ffmpeg.exe" process in my C# application to process media files. However, I'm encountering a "NullReferenceException" when running the code. I've tried various approaches, including using a try-catch block, but the exception still persists. Here's the relevant code snippet :

  


  bool isValidMedia = true;

try
{
    Process process = new Process();
    process.StartInfo.FileName = "ffmpeg.exe";
    process.StartInfo.Arguments = $"-i \"{file}\" -f null -";
    process.StartInfo.UseShellExecute = false;
    process.StartInfo.RedirectStandardOutput = true;
    process.StartInfo.CreateNoWindow = true;
    process.OutputDataReceived += (sender, e) =>
    {
        if (!string.IsNullOrEmpty(e.Data))
        {
            int startIndex = e.Data.IndexOf("samples=") + 8;
            button.Width = int.Parse(e.Data.Substring(startIndex, e.Data.IndexOf(" ") - startIndex)) / zoom * 100;
        }
        else
        {
            isValidMedia = false;
        }
    };

    process.Start();
    process.BeginOutputReadLine();
    process.WaitForExit();
}
catch
{
    isValidMedia = false;
}

if (!isValidMedia)
{
    MessageBox.Show("Not a valid media.");
    return;
}



  


  I suspect that the issue may be related to the asynchronous execution of the event handler or the initialization of the ProcessStartInfo object. Can anyone please help me identify the cause of the "NullReferenceException" and provide guidance on how to resolve it ? Thank you in advance for your assistance.

  


• Revert "lavc/nvenc : handle frame durations and AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE"

  16 juin 2023, par Timo Rothenpieler

  Revert "lavc/nvenc : handle frame durations and AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE"
  The implementation is flawed in that the frame opaque data is not in
  
  fact correctly reordered along with the packets, but is being output in
  
  packet input order, just like the dts are.
  This reverts commit 35538097038fd1e36577306d3165f38c8fa02466.
  

  • [DH] libavcodec/nvenc.c
  • [DH] libavcodec/nvenc.h
  • [DH] libavcodec/nvenc_av1.c
  • [DH] libavcodec/nvenc_h264.c
  • [DH] libavcodec/nvenc_hevc.c

• C# Process in loop reading error output, causes "No async read operation is in progress on the stream" error

  29 mai 2023, par TSLee

  I am trying to read the format of multiple video files using ffmpeg in an asynchronous operation of Process and facing an error, "No async read operation is in progress on the stream". According to https://social.msdn.microsoft.com/Forums/vstudio/en-US/c961f461-7afb-4a92-b0ae-f78c2003b5de/help-an-asynchronous-read-operation-is-already-in-progress-on-the-standardoutput-stream?forum=csharpgeneral, I think I have to use CancelErrorRead(), as BeginErrorReadLine() can't be launched more than once. I also wonder if I use this function in the wrong place, because the read operation has ended in process1.exited() ? But the operation can't proceed to the second index with this error.

  


  How could I use CancelErrorRead()/CancelOutputRead() properly and where should I place them on the code ? I also did an experiment in that I commented these two CancelRead(), and a different error "async read operation has been started on the stream" will appear.

  


              Process process1 = new Process();
            process1.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
            process1.StartInfo.CreateNoWindow = true;
            process1.StartInfo.UseShellExecute = false;
            process1.StartInfo.FileName = ".\\ffmpeg.exe";
            process1.StartInfo.WorkingDirectory = ".\\";
            process1.EnableRaisingEvents = true;
            process1.StartInfo.RedirectStandardOutput = true; //if this is true, UseShellExecute must be false. true if output should be written to StandardOutput
            process1.StartInfo.RedirectStandardError = true;
            //indicates that the associated Process has written a line that's terminated with a newline
            process1.ErrorDataReceived += new DataReceivedEventHandler(inputHandler);
            process1.Exited += (ending, p) =>
            {
                flag = true;
                process1.CancelOutputRead();
                process1.CancelErrorRead();//
            };
            foreach (String file in inputList)
            {
                if (flag == true)
                {
                    flag = false;
                    process1.StartInfo.Arguments = "-i " + " \"" + file + "\"";
                    Console.WriteLine(process1.StartInfo.Arguments);
                    process1.Start();
                    process1.BeginOutputReadLine();//
                    process1.BeginErrorReadLine();
                    process1.WaitForExit(); //for asynchronous output
                }


            }
        }
        private void inputHandler(object sender, DataReceivedEventArgs l)
        {
             cba.Append(l.Data + "\n");
             videoInput = l.Data;
             //Console.WriteLine(cba);
             //Process p = sender as Process;
             Console.WriteLine(videoInput);

             this.BeginInvoke(new MethodInvoker(() =>
             {

              if (!String.IsNullOrEmpty(videoInput))
              {
                    if (videoInput.Contains("Stream #0:0"))
                    {
                        String subvideoInput1 = 
                        videoInput.Substring(videoInput.IndexOf("Stream #0:0"));
                        String video_inputType = subvideoInput1;
                        textBox1.Text += video_inputType + System.Environment.NewLine;
                        Console.WriteLine(video_inputType);
                     }
                     if (videoInput.Contains("Stream #0:1"))
                     {
                         String subvideoInput2 = 
                         videoInput.Substring(videoInput.IndexOf("Stream #0:1"));
                         Console.WriteLine(subvideoInput2.IndexOf("\n"));
                         Console.WriteLine(subvideoInput2);
                         String audio_inputType = subvideoInput2;
                         textBox1.AppendText(audio_inputType + System.Environment.NewLine);
                         Console.WriteLine(audio_inputType);
                     }
                     if (videoInput.Contains("Duration:"))
                     {
                         String videoinputDuration = 
                         videoInput.Substring(videoInput.IndexOf("Duration:"));
                         String subvideo_inputDuration = videoinputDuration.Substring(9);
                         String inputvideoDuration = 
                     subvideo_inputDuration.Remove(subvideo_inputDuration.IndexOf("."));
                         Console.WriteLine(inputvideoDuration);
                         double totalseconds = 
                         TimeSpan.Parse(inputvideoDuration).TotalSeconds;
                    
                    

                }
            }

        }));


    }