Recherche avancée

Sur d’autres sites (8878)

• Running subprocess.Popen in a compiled script has a significant delay

  6 mai 2022, par thisismy-stackoverflow

  Edit : In this specific example, Python 3.8 is being used on Windows 10.

  


  I need to run FFprobe through subprocess.Popen so I can capture and parse the output. If I do this in a script, it runs almost instantly, but if I compile my script with PyInstaller and do the same thing, it takes over 0.8 seconds to complete. Is there a trick or any way I can execute it faster from the compiled script ? I'm willing to hear FFprobe-specific answers if they exist.

  


  This is what I'm using currently. The extra code is for ensuring FFprobe doesn't flash a console window while running (removing the console window actually made it 0.1 seconds faster on average).

  


  startupinfo = subprocess.STARTUPINFO()
startupinfo.dwFlags |= subprocess.STARTF_USESHOWWINDOW
p = subprocess.Popen(f'ffprobe -show_format -show_streams -of json "{file}"', startupinfo=startupinfo, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = p.communicate()


  


• C# app - running FFMpeg from the command line is not working

  11 avril 2017, par Dan Kahn

  I’m trying to run FFMpeg from the Command Line in C#. Previously I was running it from "CMD.exe" and it was working, but that requires a local installation of ffmpeg with configuring my System environmental variables. So I wanted to run it directly from "ffmpeg.exe". I’m using the following code (all the paths are correct), and nothing happens :

  string programToRun = "C:\\Users\\dkahn\\Documents\\PlaybackTool\\PlaybackTool\\Desktop\\Source\\Player\\Player\\ffmpeg\\ffmpeg.exe";
  
  
  
  string directoryName = "C:\\Users\\dkahn\\Documents\\PlaybackTool\\PlaybackTool\\Desktop\\Source\\Player\\test\\test1-1.mp4";
  
  
  
  string command = "@ffmpeg -i test1-1.mp4 -r 1  -s 180x101 test1-1\\output_%04d.png";
  
  
  
  Process cmd = new Process();
  
  cmd.StartInfo.FileName = programToRun;
  
  cmd.StartInfo.RedirectStandardInput = true;
  
  cmd.StartInfo.RedirectStandardOutput = true;
  
  cmd.StartInfo.CreateNoWindow = true;
  
  cmd.StartInfo.UseShellExecute = false;
  
  cmd.StartInfo.WorkingDirectory = directoryName;
  
  cmd.Start();
  
   cmd.StandardInput.WriteLine(command);
  
  cmd.StandardInput.Flush();
  
  cmd.StandardInput.Close();
  
  cmd.WaitForExit();

  Does anybody have any insight ?

• Is there a way to add/modify/delete one of the outputs of a running ffmpeg core which has multiple ones ?

  7 novembre 2022, par Edward Sternin

  The task is to stream a video feed from a webcam, watch it live on a display, then start/stop a recording of same into a file, while maintaining the live video feed.

  


  This will record a 5-s clip (with no audio), while simultaneously watching it on the screen :

  


  ffmpeg -v error -f v4l2 -framerate 30 -video_size 640x480 -t 5 -i /dev/video0 -an \
    clip.mp4 -y -map 0:v -pix_fmt yuv420p -f xv "Capturing a 5-s clip" 


  


  however I need to surround it before and after with live display :

  


  ffmpeg -v error -f v4l2 -framerate 30 -video_size 640x480 -i /dev/video0 -an \ 
    -map 0:v -pix_fmt yuv420p -f xv "Live display"


  


  which I then kill in order to launch the recording version and re-launch when that one terminates. This creates a noticeable break as one ffmpeg dies and another launches.

  


  This explains how to pause/resume ffmpeg process itself using
kill -s SIGSTOP <pid></pid> and kill -s SIGCONT <pid></pid> as needed, but what I want is to pause/resume (or start/stop) just the recording output, while keeping the display output continuous.

  


  Another way to think about it is whether it is possible to add an extra output stream to a running ffmpeg core, and either pass a time restriction to it - so it disconnects itself when done, or have an ability to delete an output from a running ffmpeg core, without killing the other outputs.