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• Subprocess call stopping asynchronously-executed Python parent process

  6 mai 2016, par Suriname0

  The following shell session demonstrates the behavior I am seeing :

  [user@compname python-test]$ cat test.py
  
  #!/usr/bin/env python
  
  import subprocess
  
  from time import sleep
  
  proc = subprocess.Popen("ffmpeg", stdout=subprocess.PIPE, stderr=subprocess.STDOUT, shell=True)
  
  print "Starting process: " + str(proc)
  
  status = proc.poll()
  
  while status is None:
  
      print "Process still running."
  
      sleep(0.01)
  
      status = proc.poll()
  
  print "Status: " + str(status)
  
  [user@compname python-test]$ python test.py
  
  Starting process: 
  
  Process still running.
  
  Process still running.
  
  Status: 1
  
  [user@compname python-test]$ python test.py &
  
  [4] 6976
  
  [user@compname python-test]$ Starting process: 
  
  Process still running.
  
  Process still running.
  
  [4]+  Stopped                 python test.py
  
  [user@compname python-test]$ ps
  
    PID TTY          TIME CMD
  
   4684 pts/101  00:00:00 python
  
   4685 pts/101  00:00:00 ffmpeg
  
   7183 pts/101  00:00:00 ps
  
  14385 pts/101  00:00:00 bash

  As you can see, when the simple test Python program is run normally, it completes successfully. When it is run asynchronously (using &), the Python process is stopped as soon as the subprocess call is complete (and poll() would return a non-None value).

  1. The same behavior occurs when using Popen.wait()
  2. The behavior is unique to ffmpeg.
  3. Both the Python process and ffmpeg are ending up stopped, as seen in the call to ps.

  Can someone help me detangle this behavior ? I don’t see anything in the documentation for the subprocess module, bash’s & operator, or ffmpeg that would explain this.

  The Python version is 2.6.6, bash is GNU bash version 4.1.2(1)-release (x86_64-redhat-linux-gnu), ffmpeg is version 3.0.1-static.

  Thank you for any help !

• ffmpeg opening video file at lower bitrate

  23 février 2018, par Xeno Boss

  I have a php page which runs ffmpeg from shell with the exec() function as follows ffmpeg -i rtsp://address:port/stream -b:v 512k output.mp4 and since many people could visit the page at once it could fire up many ffmpeg processes for different rtsp streams simultaneously which will eat up my bandwidth.
  Is there some way for me to reduce the bitrate at which the streams are opened ?

  Note : I assumed the bitrate is the most effective factor for reducing bandwidth, please correct me if you have any better suggestions.

• FFMPEG or moviepy : easiest way to remove segments using list of timestamps ?

  26 août 2020, par I Z

  I have a bunch of videos that I need to trim by removing segments that contain silence, noise, and other fluff. I don't have a GUI-based video editing tool available to me (not even Movie Maker) but I do have moviepy and ffmpeg. So if I have a list of segments I want to remove as pairs of from-to timestamps, which tool is easier to set up (either a Python script or a shell script in cygwin under Win10) to process those videos ? TIA !