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• Command is running different from expected when i use it trought Python

  17 septembre 2021, par Gustavo Marinho

  I have a code where i download a youtube video as 3gpp and convert it to a mp3, i need to use FFmpeg to do this, and it work well when using both cmd and powershell, but, when i tried to run the same command in Python, it didin't work at all.

  


  This is my command :

  


  ffmpeg -i  C:\YTDownloads\CurrentAudio.3gpp C:\YTDownloads\CurrentAudio.mp3

  


  I tried :

  


  subprocess.call(r'%SystemRoot%\system32\WindowsPowerShell\v1.0\powershell.exe ffmpeg -i  C:\YTDownloads\CurrentAudio.3gpp C:\YTDownloads\CurrentAudio.mp3', shell=True)

  


  subprocess.run(["ffmpeg","-i","C:\YTDownloads\CurrentAudio.3gpp","C:\YTDownloads\CurrentAudio.mp3]")


  


  os.system('powershell ffmpeg -i  C:\YTDownloads\CurrentAudio.3gpp C:\YTDownloads\CurrentAudio.mp3')


  


  subprocess.run([
    'ffmpeg',
    '-i', os.path.join(parent_dir, f"{newname}.3gpp"),
    os.path.join(parent_dir, f"{newname}.mp3")
]) 


  


  subprocess.call('C:\Windows\System32\powershell.exe ffmpeg -i  C:\YTDownloads\CurrentAudio.3gpp C:\YTDownloads\CurrentAudio.mp3', shell=True)


  


  all of them return some type of error, in some of them it returns that ffmpeg isn't a recognized as a internal command, in others it says that the system can't find the specified path, but none of them works, even thought it works perfectly when i use the exactly same command on cmd/powershell.

  


  sorry for my bad english :3

  


• Use ffmpeg to record 2 webcams on raspberry pi

  30 janvier 2021, par RaresBaaa

  I want to record 2 webcams using ffmpeg, i have a simple python script but it doesn't work when I run the 2 subprocesses at the same time.

  


  ROOT_PATH = os.getenv("ROOT_PATH", "/home/pi")
ENCODING = os.getenv("ENCODING", "copy")
new_dir = datetime.datetime.now().strftime("%Y_%m_%d_%H_%M_%S")
RECORDINGS_PATH1 = os.getenv("RECORDINGS_PATH", "RecordingsCam1")
RECORDINGS_PATH2 = os.getenv("RECORDINGS_PATH", "RecordingsCam2")
recording_path1 = os.path.join(ROOT_PATH, RECORDINGS_PATH1, new_dir)
recording_path2 = os.path.join(ROOT_PATH, RECORDINGS_PATH2, new_dir)
os.mkdir(recording_path1)
os.mkdir(recording_path2)
segments_path1 = os.path.join(recording_path1, "%03d.avi")
segments_path2 = os.path.join(recording_path2, "%03d.avi")
record1 = "ffmpeg -nostdin -i /dev/video0 -c:v {} -an -sn -dn -segment_time 30 -f segment {}".format(ENCODING, segments_path1)
record2 = "ffmpeg -nostdin -i /dev/video2 -c:v {} -an -sn -dn -segment_time 30 -f segment {}".format(ENCODING, segments_path2)
subprocess.Popen(record1, shell=True)
subprocess.Popen(record2, shell=True)


  


  Also, i tried capturing the 2 sources side by side but it gives the error :`Filtering and streamcopy cannot be used together.

  


• subprocess called from multiprocess not finishing

  24 juin 2020, par Pavel Komarov

  I've got a set of videos from which I'm trying to pull random frames. There are a lot of videos, so I want to work in parallel, and ffmpeg can splice out the frames for me, so here's the important part of the code :

  


  import os
from tqdm import tqdm
from joblib import Parallel, delayed
from multiprocessing import current_process
from subprocess import Popen

vids_dir = 'just a string'
out_dir = 'another string'

def process_each(f):
    temp = 'temp' + str(current_process()._identity[0])
    os.mkdir(temp)

    proc = Popen(['ffmpeg -i ' + vids_dir + '/' + f + ' ' + temp + '/' + f[:-4] + '_%03d.jpg &> /dev/null'], shell=True) # convert to frames
    proc.wait()

    # do stuff

    os.system('rm -rf ' + temp) # clean up


Parallel(n_jobs=10)(delayed(process_each)(f) for f in tqdm(os.listdir(vids_dir)))


  


  I can print out the command being passed to Popen and execute it in a shell, and it works. I can open a python3 session and call the command from Popen or subprocess.call or even os.system, and it works. I can even set n_jobs=1 in my Parallel, and it works.

  


  But the moment I actually parallelize this, I find ffmpeg doesn't flush its full results to the temporary folders ; it only gets the first one or few frames.

  


  What on earth could be going on ? subprocess and multiprocessing should be able to mix this way.