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• Process.WaitForExitAsync stucks infinitely while calling ffmpeg on Windows

  8 novembre 2022, par Iskander Raimbaev

  I am working with ffmpeg via C#'s Process class.

  


  I have a script that runs ffmpeg to generate thumbnails from video. Initially it was called manually from command line - .\ffmpeg.exe -i .\input.mp4 -ss 00:00:01.000 -vframes:v 1 output.png, it starts ffmpeg instance, outputs some warnings/errors during the execution :

  


  [image2 @ 000001e51095ec80] The specified filename 'output.png' does not contain an image sequence pattern or a pattern is invalid.
[image2 @ 000001e51095ec80] Use a pattern such as %03d for an image sequence or use the -update option (with -frames:v 1 if needed) to write a single image.
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=   0x
video:73kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown


  


  but anyway exits the process and correctly generates thumbnail image at output.png.

  


  I want to execute it from C#.
Let's see the code :

  


  var ffmpegProcess = new Process
{
     StartInfo = new ProcessStartInfo
     {
         FileName = _config.FfmpegExecutablePath,
         Arguments = CreateArgumentsForFfmpegProcessToRun(videoTempFilePath, thumbnailTempFilePath),
         RedirectStandardError = true,
         RedirectStandardInput = true,
         RedirectStandardOutput = true,
         UseShellExecute = false,
         CreateNoWindow = true
     },
     EnableRaisingEvents = true
 };

 ffmpegProcess.Start();
 await ffmpegProcess.WaitForExitAsync();


  


  Method CreateArgumentsForFfmpegProcessToRun returns exactly the same arguments as in the script above -i .\input.mp4 -ss 00:00:01.000 -vframes:v 1 output.png.

  


  However, when I run this code, it stucks/blocked at line ffmpegProcess.WaitForExitAsync() infinitely and no output written to output path.
If I omit WaitForExitAsync call and just go to the next line, then it doesn't stuck and writes the output as expected and finish the process with -1 exit code.

  


  I am trying to figure out why block/stuck happens and what is the best way to resolve this situation ? As far I know, WaitForExitAsync should return as process ends, no matter how process ends - 0 or another exit code, am I right ?

  


  Update #1 :
Community advised to search if somewhere up the stack I am blocking my code. I wrote xunit-test and it still stucks.

  


  [Theory]
[InlineData("assets/input.mp4", "assets/ffmpeg.exe")]
public async Task CreateThumbnailFromVideo(string videoFilePath, string ffmpegExePath)
{
    var config = new VideoThumbnailServiceConfig
    {
         FfmpegExecutablePath = ffmpegExePath,
         ThumbnailImageExtension = ".png"
    };

    var sut = new VideoThumbnailService(config);

    using var fileStream = File.OpenRead(videoFilePath);
    await sut.CreateThumbnailFromVideo(fileStream);
 } 


  


  Inside sut.CreateThumbnailFromVideom I call process start method and awaits WaitForExitAsync().

  


• How to use run ffmpeg command in ios

  30 mai 2017, par pramod

  I had successfully build ffmpeg into xcode but I didn’t get idea , how to execute command into project.I research hard on it and fined how to play video using encoding and decoding,but did not get idea how to run command.

• How to use run ffmpeg command in ios

  31 janvier 2017, par pramod

  I had successfully build ffmpeg into xcode but I didn’t get idea , how to execute command into project.I research hard on it and fined how to play video using encoding and decoding,but did not get idea how to run command.