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In the code I written in WPF, I run some filter in FFmpeg, If I run the command in terminal (PowerShell or cmd prompt) It will give me information line by line what's going on.

I am calling the process from C# code and it's work fine. The problem I have with my code is actually I am not able to get any output from the process I run.

I have tried some answers from StackOverflow for FFmpeg process. I see 2 opportunities in my code. I can either fix it by Timer approach or secondly hook an event to OutputDataReceived.

I tried OutputDataReceived event, My code never got it worked. I tried Timer Approach but still, it's not hitting my code. Please check the code below

        _process = new Process
        {
            StartInfo = new ProcessStartInfo
            {
                FileName = ffmpeg,
                Arguments = arguments,
                UseShellExecute = false,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                CreateNoWindow = true,
            },
            EnableRaisingEvents = true
        };

        _process.OutputDataReceived += Proc_OutputDataReceived;

        _process.Exited += (a, b) =>
        {
            System.Threading.Tasks.Task.Run(() =>
            {
                System.Threading.Tasks.Task.Delay(5000);
                System.IO.File.Delete(newName);
            });

            //System.IO.File.Delete()
        };

        _process.Start();
        _timer = new Timer();
        _timer.Interval = 500;
        _timer.Start();
        _timer.Tick += Timer_Tick;
    }


    private void Timer_Tick(object sender, EventArgs e)
    {
        while (_process.StandardOutput.EndOfStream)
        {
           string line = _process.StandardOutput.ReadLine();
        }
        // Check the process.

    }
Anirudha Gupta
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1 Answers1

7

ffmpeg seems to output status updates on StandardError rather than StandardOutput.

I managed to get updates from it using the following code:

process = new Process
{
    StartInfo = new ProcessStartInfo
    {
        FileName = ffmpeg,
        Arguments = args,
        UseShellExecute = false,
        RedirectStandardOutput = true,                    
        CreateNoWindow = false,
        RedirectStandardError = true
    },
    EnableRaisingEvents = true
};

process.Start();

string processOutput = null;
while ((processOutput = process.StandardError.ReadLine()) != null)
{
    // do something with processOutput
    Debug.WriteLine(processOutput);
}
steve16351
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  • Thanks for the help, This code is showing the output, Is there a way to check the progress in percentage. – Anirudha Gupta Jul 12 '18 at 09:52
  • As far as I can see only by parsing the updates that ffmpeg emits. I'm no expert on ffmpeg, but in the example I tried it outputs the total duration of the file at the start, and then ongoing updates relay the time of the file it has processed so far. So by parsing those, you could get an idea of completion from that. Based on what I saw I've updated the code to get that. – steve16351 Jul 12 '18 at 10:24
  • I am doing overlay (filter_overlay), it shows me 3,4 stop, I think it will be better if I use an indeterminate progress bar. – Anirudha Gupta Jul 12 '18 at 10:33