Trying to grab the output of ffprobe with Python

Question

I'm trying to capture the output from ffprobe. First, I build my command:

>>> print cmd
['C:\\Program Files\\ffmpeg\\bin\\ffprobe.exe', 'somefile.mov']

Then I use check_output to grab the output:

>>> import subprocess as sp
>>> output = sp.check_output(cmd)
ffprobe version N-66673-gf0d1b3a Copyright (c) 2007-2014 the FFmpeg developers
  built on Oct  6 2014 22:10:42 with gcc 4.9.1 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfi
g --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-lib
opencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinge
r --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --
enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-
libx265 --enable-libxavs --enable-libxvid --enable-zlib
  libavutil      54.  9.100 / 54.  9.100
  libavcodec     56.  3.101 / 56.  3.101
  libavformat    56.  7.104 / 56.  7.104
  libavdevice    56.  1.100 / 56.  1.100
  libavfilter     5.  1.102 /  5.  1.102
  libswscale      3.  1.100 /  3.  1.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  1.100 / 53.  1.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'somefile.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 512
    compatible_brands: qt
    encoder         : Lavf56.7.104
  Duration: 00:20:54.46, start: 0.000000, bitrate: 1734 kb/s
    Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720, 1617 kb/s, 24 fps, 24 tbr, 1
2288 tbn, 24576 tbc (default)
    Metadata:
      handler_name    : DataHandler
    Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 113 kb/s (default)
    Metadata:
      handler_name    : DataHandler

However when I print the output, I get nothing:

>>> print output

I got the same result with Popen and communicate():

 >>> output = sp.Popen(cmd, stdout=sp.PIPE)
 >>> output.communicate()
 ('', None)

Well, I guess it's not really nothing. Looks like I got a blank string back?

score 0 · Answer 1 · answered Oct 16 '14 at 22:18

Weird...I can catch it with stderr?

>>> output = sp.Popen(cmd, stdout=sp.PIPE, stderr=sp.PIPE)
>>> output.communicate()
('', "ffprobe version N-66673-gf0d1b3a Copyright (c) 2007-2014 the FFmpeg developers\r\n  built on Oct  6 2014 22:10:42
with gcc 4.9.1 (GCC)\r\n  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-
bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-lib
bs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable
-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp
 --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab
--enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --
enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-zlib\r\n  libavutil      54.  9.100 / 54.  9.
100\r\n  libavcodec     56.  3.101 / 56.  3.101\r\n  libavformat    56.  7.104 / 56.  7.104\r\n  libavdevice    56.  1.1
00 / 56.  1.100\r\n  libavfilter     5.  1.102 /  5.  1.102\r\n  libswscale      3.  1.100 /  3.  1.100\r\n  libswresamp
le   1.  1.100 /  1.  1.100\r\n  libpostproc    53.  1.100 / 53.  1.100\r\nInput #0, mov,mp4,m4a,3gp,3g2,mj2, from 'somefile.mov':\r\n  Metadata:\r\n    major_brand     : qt  \r\n    minor_version   : 512\r\n
  compatible_brands: qt  \r\n    encoder         : Lavf56.7.104\r\n  Duration: 00:20:54.46, start: 0.000000, bitrate: 17
34 kb/s\r\n    Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720, 1617 kb/s, 24 fps
, 24 tbr, 12288 tbn, 24576 tbc (default)\r\n    Metadata:\r\n      handler_name    : DataHandler\r\n    Stream #0:1(eng)
: Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 113 kb/s (default)\r\n    Metadata:\r\n      handler_name    :
 DataHandler\r\n")

I guess all of the output from ffprobe that I see is actually getting pumped through stderr.

Trying to grab the output of ffprobe with Python

1 Answers1