ffmpeg: you are trying to apply an input option to an output file or vice versa. Move this option before the file it belongs to.

[sofeikov]

I'm trying to get imageio reading only I-frames with ffmpeg plugin. Therefore, I'm using the following line in python:

video_reader = imageio.get_reader(video_path, 'ffmpeg', ffmpeg_params=['-vf', 'select eq(pict_type\,PICT_TYPE_I)'])

During the initialisation I get the following message from ffmpeg:

ffmpeg version 3.3.3 Copyright (c) 2000-2017 the FFmpeg developers built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3) configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libfreetype --enable-gnutls --disable-ffserver --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libtheora --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvidstab --enable-libwavpack --enable-nvenc --enable-libzimg libavutil 55. 58.100 / 55. 58.100 libavcodec 57. 89.100 / 57. 89.100 libavformat 57. 71.100 / 57. 71.100 libavdevice 57. 6.100 / 57. 6.100 libavfilter 6. 82.100 / 6. 82.100 libavresample 3. 5. 0 / 3. 5. 0 libswscale 4. 6.100 / 4. 6.100 libswresample 2. 7.100 / 2. 7.100 libpostproc 54. 5.100 / 54. 5.100 Option vf (set video filters) cannot be applied to input url /home/konsof01/Work/FaceBackend/TestData/TestMedia/me.mp4 -- you are trying to apply an input option to an output file or vice versa. Move this option before the file it belongs to. Error parsing options for input file /home/konsof01/Work/FaceBackend/TestData/TestMedia/me.mp4. Error opening input files: Invalid argument

The end of this message clearly says that the given option is being put into a wrong place. Is this by-design or am I doing something wrong?

Is it a good idea to have a way to tell that some options are for output files, not for input?

Thanks,
Konstantin

[sofeikov]

I strongly suspect that the problem is here

https://github.com/imageio/imageio/blob/master/imageio/plugins/ffmpeg.py#L423

All additional arguments given are being put in front of filename given.

[almarklein]

In #321 I added that one can specify input_params and output_params. The old ffmpeg_params still works (maps to input_params when reading and output_params when writing).