Ffmpeg-python: How do I read back errors?

[roman-ku]

When I get this back from ffmpeg ffprobe error (see stderr output for detail) I do not know how to check the stderr output for the details.

import sys

import ffmpeg
from ffmpeg import Error as FFmpegError

try:
    duration = ffmpeg.probe('https://www.youtube.com/watch?v=cv4123_39ddfa324LB23MsYg')['format']['duration']

except FFmpegError as e:
    print(e)

    # doesn't work
    # for line in sys.stderr:
        # print(line)

    # doesn't work
    # data = sys.stderr.readlines()
    # print(data)

Couldn't find an example of this in the documentation and couldn't figure it out myself.

[evictor]

With some finagling I came up with this:

1. Pass args capture_stdout=True, capture_stderr=True to run()
2. Theoretically the run() func returns tuple (out, err) so you can receive those; however...
3. If the return code is nonzero the function throws so you should probably catch that and print:

            try:
                ffmpeg.input(...) \
                    .output(...) \
                    .run(capture_stdout=True, capture_stderr=True)
            except ffmpeg.Error as e:
                print('stdout:', e.stdout.decode('utf8'))
                print('stderr:', e.stderr.decode('utf8'))
                raise e

[AfcEagle]

tanx was usefull
for me gave this..
what this error means ...

stdout:
stderr: ffmpeg version 4.2.1 Copyright (c) 2000-2019 the FFmpeg developers

built with gcc 9.1.1 (GCC) 20190807

configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt

libavutil 56. 31.100 / 56. 31.100

libavcodec 58. 54.100 / 58. 54.100

libavformat 58. 29.100 / 58. 29.100

libavdevice 58. 8.100 / 58. 8.100

libavfilter 7. 57.100 / 7. 57.100

libswscale 5. 5.100 / 5. 5.100

libswresample 3. 5.100 / 3. 5.100

libpostproc 55. 5.100 / 55. 5.100

[image2 @ 05fe3ec0] Pattern type 'glob' was selected but globbing is not supported by this libavformat build

1.jpg: Function not implemented

[wangjk666]

Hi, I also run into this problem, have you fixed it?

[CodeStrumpet]

Just ran into this as well (could not figure out how to read stderr coming from probe). Finally (after a lot of unsuccessful googling) I found the answer in a nicely placed comment in the the source code:

From ffmpeg-python/ffmpeg/_probe.py:

    Raises:
        :class:`ffmpeg.Error`: if ffprobe returns a non-zero exit code,
            an :class:`Error` is returned with a generic error message.
            The stderr output can be retrieved by accessing the
            ``stderr`` property of the exception.

So this is what worked for me:

try:
    probe = ffmpeg.probe(video_path)
    video_stream = next((stream for stream in probe['streams'] if stream['codec_type'] == 'video'), None)
    width = int(video_stream['width'])
    height = int(video_stream['height'])
    duration = float(video_stream['duration'])
except ffmpeg.Error as e:
    print(e.stderr)