Getting realtime output from ffmpeg to be used in progress bar (PyQt4, stdout)

Question

I\'ve looked at a number of questions but still can\'t quite figure this out. I\'m using PyQt, and am hoping to run ffmpeg -i file.mp4 file.avi and get the out

Answer 1

In this specific case for capturing ffmpeg's status output (which goes to STDERR), this SO question solved it for me: FFMPEG and Pythons subprocess

The trick is to add universal_newlines=True to the subprocess.Popen() call, because ffmpeg's output is in fact unbuffered but comes with newline-characters.

cmd = "ffmpeg -i in.mp4 -y out.avi"
process = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT,universal_newlines=True)
for line in process.stdout:
    print(line)

Also note that in this code sample the STDERR status output is directly redirected to subprocess.STDOUT