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• Python subprocesses only start once I Ctrl-C the program ?

  4 février 2016, par slhck

  I’m trying to run a few ffmpeg commands in parallel, using Cygwin and Python 2.7.

  This is roughly what I have :

  import subprocess
  
  processes = set()
  
  
  
  commands = ["ffmpeg -i input.mp4 output.avi", "ffmpeg -i input2.mp4 output2.avi"] 
  
  
  
  for cmd in commands:
  
    processes.add(
  
      subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
  
    )
  
  
  
  for process in processes:
  
    if process.poll() is None:
  
      process.wait()

  Now, once I am at the end of this code, the whole program waits. All the ffmpeg processes are created, but they’re idle, i.e., using 0% CPU. And the Python program just keeps waiting. Only when I hit Ctrl-C, it suddenly starts encoding.

  What am I doing wrong ? Do I have to "send" something to the processes to start them ?

• How to solve file path error while using ffprobe to find length of video file in python ?

  4 février 2018, par Mitchell Faas

  So, I’m trying to find the length of a video file by the methods discussed here : How to get the duration of a video in Python ?, Using ffmpeg to obtain video durations in python. But in doing so I run in to a problem which I haven’t been able to solve : I get

  FileNotFoundError:[WinError 2] The system cannot find the file specified

  after trying a bunch of troubleshooting steps I’ve started running in IPython and in cmd seperately to see where things might break down. Using a stripped down version of this code in IPython gives me

  In [11]: subprocess.Popen([ffmpeg_path+'ffprobe'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  Out[11]: 

  which seems to be fine, as is CMD at this point. So to adding slight complexity :

  In [17]: subprocess.Popen([ffmpeg_path+'ffprobe -i "F:/tst.mp4"'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  ---------------------------------------------------------------------------
  
  FileNotFoundError                         Traceback (most recent call last)
  
   in <module>()
  
  ----> 1 subprocess.Popen([ffmpeg_path+'ffprobe -i "F:/tst.mp4"'], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  
  
  C:\Python\Anaconda3\lib\subprocess.py in __init__(self, args, bufsize, executable, stdin, stdout, stderr, preexec_fn, close_fds, shell, cwd, env, universal_newlines, startupinfo, creationflags, restore_signals, start_new_session, pass_fds, encoding, errors)
  
      705                                 c2pread, c2pwrite,
  
      706                                 errread, errwrite,
  
  --> 707                                 restore_signals, start_new_session)
  
      708         except:
  
      709             # Cleanup if the child failed starting.
  
  
  
  C:\Python\Anaconda3\lib\subprocess.py in _execute_child(self, args, executable, preexec_fn, close_fds, pass_fds, cwd, env, startupinfo, creationflags, shell, p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, unused_restore_signals, unused_start_new_session)
  
      988                                          env,
  
      989                                          cwd,
  
  --> 990                                          startupinfo)
  
      991             finally:
  
      992                 # Child is launched. Close the parent's copy of those pipe
  
  
  
  FileNotFoundError: [WinError 2] The system cannot find the file specified
  
  </module>

  This crashes IPython. Running the very same command ffprobe -i "F:/tst.mp4" in CMD works like a charm.

  Here’s what I tried : Changing / to \ and \ , adding and removing quotes around the file path, changing the path to C :\tst.mp4.

  Running the command os.system(ffmpeg_path+'ffprobe -i "F:/tst.mp4") does work.

  What could possibly be going wrong here ?

• py2app compiled script with ffmpeg not working (mac)

  18 avril 2020, par martijnlambada

  I'm currently experiencing a lot of difficulties getting ffmpeg-python to work when compiling my script with Py2App. The attached script works fine when run from the command line, as does the terminal version found in the application bundle. When double clicking the app though, it just gives me a popup with (the not very descriptive) "Error". I've tried all possible solutions found in related posts including compiling the script with the "—emulate-shell-environment" flag. So far no luck. 
Details : Python 2.7.16 | macOs 10.14.6 | Latest version of ffmpeg & py2app.

  



  Appreciate the help !

  



  Thanks, martijn

  



  import ffmpeg

stream = ffmpeg.input('input.mp4')
stream = ffmpeg.filter(stream,'scale', 800, 450)
stream = ffmpeg.output(stream, 'output2.mp4')
ffmpeg.run(stream)