I have the following command:
$ ffmpeg -i http://url/1video.mp4 2>&1 | perl -lane 'print $1 if /(\d+x\d+)/'
640x360
I'm trying to set the output of this command into a python variable. Here is what I have so far:
>>> from subprocess import Popen, PIPE
>>> p1 = Popen(['ffmpeg', '-i', 'http://url/1video.mp4', '2>&1'], stdout=PIPE)
>>> p2=Popen(['perl','-lane','print $1 if /(\d+x\d+)/'], stdin=p1.stdout, stdout=PIPE)
>>> dimensions = p2.communicate()[0]
''
What am I doing incorrectly here, and how would I get the correct value for dimensions?
In general, you can replace a shell pipeline with this pattern:
p1 = Popen(["dmesg"], stdout=PIPE)
p2 = Popen(["grep", "hda"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close() # Allow p1 to receive a SIGPIPE if p2 exits.
output = p2.communicate()[0]
However, in this case, no pipeline is necessary:
import subprocess
import shlex
import re
url='http://url/1video.mp4'
proc=subprocess.Popen(shlex.split('ffmpeg -i {f}'.format(f=url)),
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
dimensions=None
for line in proc.stderr:
match=re.search(r'(\d+x\d+)',line)
if match:
dimensions=match.group(1)
break
print(dimensions)
No need to call perl
from within python.
If you have the output from ffmpeg in a variable, you can do something like this:
print re.search(r'(\d+x\d+)', str).group()
Note the “ shell
” argument to subprocess.Popen
: this specifies whether the command you pass is parsed by the shell or not.
That “ 2>&1
” is one of those things that needs to be parsed by a shell, otherwise FFmpeg (like most programs) will try to treat it as a filename or option value.
The Python sequence that most closely mimics the original would probably be more like
p1 = subprocess.Popen("ffmpeg -i http://url/1video.mp4 2>&1", shell = True, stdout = subprocess.PIPE)<BR>
p2 = subprocess.Popen(r"perl -lane 'print $1 if /(\d+x\d+)/'", shell = True, stdin = p1.stdout, stdout = subprocess.PIPE)<BR>
dimensions = p2.communicate()[0]
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