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• ffmpeg process how to read from pipe to pipe in c#

  28 janvier 2024, par greg

  I need to read audio data from stream 1 to stream 2 passing the data through ffmpeg.
It works great when i input data from file and output to pipe :

  


  Process? CreateStream()
{
    return Process.Start(new ProcessStartInfo
    {
        FileName = @"sources\ffmpeg",
        Arguments = @"-i input.mp3 -f s16le pipe:1",
        UseShellExecute = false,
        RedirectStandardOutput = true
    });
}


  


  Or when i input data from pipe and output to file :

  


  Process? CreateStream()
{
    return Process.Start(new ProcessStartInfo
    {
        FileName = @"sources\ffmpeg",
        Arguments = @"-i pipe: -f s16le output.file",
        UseShellExecute = false,
        RedirectStandardInput = true
    });
}


  


  But if i try to do both :

  


  Process? CreateStream()
{
    return Process.Start(new ProcessStartInfo
    {
        FileName = @"sources\ffmpeg",
        Arguments = @"-i pipe:0 -f s16le pipe:1",
        UseShellExecute = false,
        RedirectStandardInput = true,
        RedirectStandardOutput = true
    });
}


  


  Runtime will hang in place printing :

  


  


  Input #0, matroska,webm, from 'pipe:0' :
Metadata :
encoder : google/video-file
Duration : 00:04:15.38, start : -0.007000, bitrate : N/A
Stream #0:0(eng) : Audio : opus, 48000 Hz, stereo, fltp (default)
Stream mapping :
Stream #0:0 -> #0:0 (opus (native) -> pcm_s16le (native))

  


  Output #0, s16le, to 'pipe:1' :
Metadata :
encoder : Lavf59.27.100
Stream #0:0(eng) : Audio : pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s (default)
Metadata :
encoder : Lavc59.37.100 pcm_s16le

  


  


  main function code (it is the same for all examples) :

  


  async Task Do()
{
    using (var ffmpeg = CreateStream())
    {
        if (ffmpeg == null) return;

        using (var audioStream = GetAudioStream())
        {
            await audioStream.CopyToAsync(ffmpeg.StandardInput.BaseStream);
            ffmpeg.StandardInput.Close();
        }

        //runtime will hang in here

        Console.WriteLine("\n\ndone\n\n"); //this won't be printed

        using (var outputStream = CreatePCMStream())
        {
            try
            {
                await ffmpeg.StandardOutput.BaseStream.CopyToAsync(outputStream);
            }
            finally
            {
                await outputStream.FlushAsync();
            }
        }
    }
}


  


  And the most interesting is if i remove RedirectStandardOutput = true string programm will work as expected printing a bunch of raw data to the console.

  


  I'd like to solve this problem without using any intermediate files and so on.

  


• php run two commands in backgorund one by one

  30 mars 2022, par RednBlack

  I have a problem in php/linux, described below :

  


  I have to execute a linux command through shell_exec and run two commands.

  


  $command1 = "ffmpeg -y -nostdin -hide_banner -re -i file.mp4 -c:a copy -c:v copy -f mpegts udp://127.0.0.1:1235 >/dev/null 2>>error.log & echo $! > file.pid";

$command2 = "php /home/update.php file.mp4 &"

shell_exec("(".$command1.") && (".$command2.")");


  


  But they both get executed in same time I tried with semi-colon ( ;) operator but same result.

  


  What I want to achieve is run first command no mater, if finished or exit with error then run second command, but both put on background so php will not hang.

  


  Thank you.

  


• avfilter/vf_extractplanes : switch to activate()

  7 mars 2022, par Paul B Mahol

  avfilter/vf_extractplanes : switch to activate()
  Fixes hang at end of input with this command :
  ffmpeg -f lavfi -i testsrc2=d=50,format=yuv444p -lavfi \
  
  "extractplanes=y+u+v[y][u][v] ;[y]tpad=start=0[y] ;[u]tpad=start=0[u] ;[v]negate[v] ;[y][u][v]vstack=3" -f null -
  

  • [DH] libavfilter/vf_extractplanes.c