[SOLVED] ffmpeg can't find opencv

timsoft · 01-07-2019, 10:09 AM

i'm running on fully patched slackware 14.2 64bit.
the ffmpeg slackbuild is complaining that pkg-config can't find opencv

Code:

patching file configure
patching file libavcodec/libopenjpegdec.c
patching file libavcodec/libopenjpegenc.c
patching file libavcodec/libfdk-aacenc.c
ERROR: opencv not found using pkg-config

If you think configure made a mistake, make sure you are using the latest
version from Git.  If the latest version fails, report the problem to the
ffmpeg-user@ffmpeg.org mailing list or IRC #ffmpeg on irc.freenode.net.
Include the log file "config.log" produced by configure as this will help
solve the problem.

it is actually called opencv4.pc in /usr/lib64/pkgconfig/
but I have tried copying opencv4.pc renaming it opencv.pc, but that didn't work. I also tried replacing " opencv " with " opencv4 " in the ffmpeg configure file prior to running it, but that didn't help apart from it complained it couldn't find opencv4 instead of opencv
running

Code:

pkg-config --exists opencv4&&echo "ok"

produces ok as you would expect, and

Code:

pkg-config --list-all|grep opencv

produces

Code:

opencv4                             OpenCV - Open Source Computer Vision Library

so pkgconfig can definitely find opencv4 even if the build script or ffmpeg configure system can't! I had a look at config.log, and tailing the last 17 lines gives

Code:

check_pkg_config opencv opencv/cxcore.h cvCreateImageHeader
pkg-config --exists --print-errors opencv
check_func_headers opencv/cxcore.h cvCreateImageHeader -I/usr/include/opencv4/opencv -I/usr/include/opencv4 -lopencv_gapi -lopencv_stitching -lopencv_videostab -lopencv_structured_light -lopencv_xphoto -lopencv_superres -lopencv_line_descriptor -lopencv_bioinspired -lopencv_rgbd -lopencv_fuzzy -lopencv_hdf -lopencv_cvv -lopencv_xobjdetect -lopencv_phase_unwrapping -lopencv_hfs -lopencv_stereo -lopencv_tracking -lopencv_datasets -lopencv_ml -lopencv_saliency -lopencv_bgsegm -lopencv_aruco -lopencv_ccalib -lopencv_img_hash -lopencv_shape -lopencv_surface_matching -lopencv_reg -lopencv_freetype -lopencv_face -lopencv_photo -lopencv_optflow -lopencv_ximgproc -lopencv_video -lopencv_plot -lopencv_dpm -lopencv_objdetect -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_imgproc -lopencv_flann -lopencv_core
check_ld cc -I/usr/include/opencv4/opencv -I/usr/include/opencv4 -lopencv_gapi -lopencv_stitching -lopencv_videostab -lopencv_structured_light -lopencv_xphoto -lopencv_superres -lopencv_line_descriptor -lopencv_bioinspired -lopencv_rgbd -lopencv_fuzzy -lopencv_hdf -lopencv_cvv -lopencv_xobjdetect -lopencv_phase_unwrapping -lopencv_hfs -lopencv_stereo -lopencv_tracking -lopencv_datasets -lopencv_ml -lopencv_saliency -lopencv_bgsegm -lopencv_aruco -lopencv_ccalib -lopencv_img_hash -lopencv_shape -lopencv_surface_matching -lopencv_reg -lopencv_freetype -lopencv_face -lopencv_photo -lopencv_optflow -lopencv_ximgproc -lopencv_video -lopencv_plot -lopencv_dpm -lopencv_objdetect -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_imgproc -lopencv_flann -lopencv_core
check_cc -I/usr/include/opencv4/opencv -I/usr/include/opencv4
BEGIN /tmp/ffconf.XXzVWgeR.c
    1   #include <opencv/cxcore.h>
    2   #include <stdint.h>
    3   long check_cvCreateImageHeader(void) { return (long) cvCreateImageHeader; }
    4   int main(void) { int ret = 0;
    5    ret |= ((intptr_t)check_cvCreateImageHeader) & 0xFFFF;
    6   return ret; }
END /tmp/ffconf.XXzVWgeR.c
gcc -D_ISOC99_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600 -DPIC -O2 -fPIC -std=c99 -fomit-frame-pointer -fPIC -pthread -I/usr/include/p11-kit-1 -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/fribidi -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/harfbuzz -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/bs2b -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/harfbuzz -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/harfbuzz -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/fribidi -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/opencv4/opencv -I/usr/include/opencv4 -c -o /tmp/ffconf.XXzsAyaV.o /tmp/ffconf.XXzVWgeR.c
/tmp/ffconf.XXzVWgeR.c:1:27: fatal error: opencv/cxcore.h: No such file or directory
compilation terminated.
ERROR: opencv not found using pkg-config

so it is trying to compile a test program, however /usr/include/opencv4/opencv does not exist (it is /usr/inlcude/opencv4/opencv2) and neither does cxcore.h exist - the nearest thing to it is core.hpp
It appears that the test case for opencv is not applicable to opencv (version 4)
has anyone managed to get ffmpeg compiling with opencv ?

ponce · 01-07-2019, 10:24 AM

I think (I may be wrong) opencv-4.x is just not usable by ffmpeg as it's too new, so maybe your best option is to avoid passing ffmpeg.SlackBuild the parameter OPENCV=yes

bassmadrigal · 01-07-2019, 10:26 AM

I'm guessing you have opencv v4 installed and that will probably only work with ffmpeg v4. Try installing opencv-legacy from SBo and see if it picks that up. If it does, you may want to ping the maintainer to have him change the optional dependency for opencv to opencv-legacy.

timsoft · 01-07-2019, 11:03 AM

will do. I'll report back on progress (i've uninstalled opencv4 and opencv-legacy is at 14%)

timsoft · 01-07-2019, 02:12 PM

well thanks bassmadrigal and ponce for looking. indeed using opencv-legacy for ffmpeg (and frei0r) allows ffmpeg to complete.
After rebuilding frei0r with opencv-legacy, and then building ffmpeg with all options, i rebuilt transcode, then vid.stab and then rebuilt ffmpeg the third time. Now it should pretty much have the kitchen sink!
I'd better let Heinz know that the optional dep for ffmpeg should be opencv-legacy not opencv as it is too new.

in-fact ponce, if you're reading this, as the frei0r slackbuild maintainer, it might be worth mentioning in the frei0r readme that if people are using frei0r with ffmpeg<4 then they probably want to use opencv-legacy instead of opencv for that optional dep.
Of course it has brought to my attention there is ffmpeg4 but I have no idea if that works with audacity or vlc so I'll leave it for now. It's taken long enough for this version.

oldpink · 04-10-2019, 05:24 AM

I am currently using ffmpeg version 4.1.3 with no trouble at all with Auadacity and VLC (not to mention SMPlayer and various audio/visual viewers and editors), but I'm using my own hand customized SlackBuild and not the one on from Andreas Guldstrand up on slackbuilds.org.
The slackbuilds.org version has customized directories for the files, where my customized build puts everything directly in the standard /usr/lib64 /usr/include /usr/share directories.
I can tell you that my build uses as many of the optional dependencies as I could possibly build it with, and I can say that I have had no success building with --enable-opencv when using any of the OpenCV version 4.x, so (as with you) I have had to use OpenCV version 3.x (specifically, version 3.4.5) in order to build ffmpeg with that option.
I was able to get the build further along by making a symbolic link /usr/include/opencv2 pointed to /usr/include/opencv4/opencv2, but the configure phase of the build still fails with a complaint about requiring C++11, but even when I rebuilt and installed OpenCV by adding "-std=c++11" as a CXXFLAG, then tried building ffmpeg, both with and with the same CXXFLAG addition, but it still fails in the configure phase.
It's not really a big deal using the somewhat older version of OpenCV, but it's still puzzling what is causing the error, and I like to keep things pretty current.
Just thought I'd give you more info to use.