opencv: Building Opencv with ffmpeg built from source gives linking errors

Hi, I’m trying build opencv to used it on ASW Lambda. Opencv is going to be uploaded as a zip file so I’m doing a static build with BUILD_SHARED_LIBS=OFF. I set up WITH_FFMPEG=YES as i will process some video files. I didn’t want to install ffmpeg with apt-get as I want to have control on where my libraries are installed. I’ve downloaded ffmpeg and installed it from source to get the libavcodec, libavformat, libavutil and libswscale. I installed it as follow:

./configure --prefix=ffmpeg_build --disable-yasm --enable-shared --cc="gcc -fPIC"

I also did:

export LD_LIBRARY_PATH=/path/ffmpeg/ffmpeg_build/lib
export PKG_CONFIG_PATH=/path/ffmpeg/ffmpeg_build/lib/pkgconfig

I can see ffmpeg was well installed by running ./ffmpeg:

ffmpeg version N-77722-g3ec5d8f Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --prefix=ffmpeg_build --disable-yasm --enable-shared --cc='gcc -fPIC'
  libavutil      55. 12.100 / 55. 12.100
  libavcodec     57. 22.100 / 57. 22.100
  libavformat    57. 21.101 / 57. 21.101
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 23.100 /  6. 23.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101

Now I’m trying to build opencv and link ffmpeg but it looks like it can’t find it. Using the cmake UI i can even specify the path of the libraries as follow.

FFMPEG_CODEC_LIB              /home/ubuntu/test_lambda/ffmpeg/ffmpeg_build/lib/libavcodec.so.57                               
 FFMPEG_FORCE_TCP            ON                                                                                           
 FFMPEG_FORMAT_LIB           /home/ubuntu/test_lambda/ffmpeg/ffmpeg_build/lib/libavformat.so.57                              
 FFMPEG_INCLUDE_DIR         /home/ubuntu/test_lambda/ffmpeg/ffmpeg_build/include                                         
 FFMPEG_LIB_DIR                   /home/ubuntu/test_lambda/ffmpeg/ffmpeg_build/include/../lib                                  
 FFMPEG_SWSCALE_LIB        /home/ubuntu/test_lambda/ffmpeg/ffmpeg_build/lib/libswscale.so.4                               
 FFMPEG_UTIL_LIB                  /home/ubuntu/test_lambda/ffmpeg/ffmpeg_build/lib/libavutil.so.55

But running the cmake command give the following:

Video I/O:
--     DC1394 1.x:     NO
--     DC1394 2.x:     NO
--     FFMPEG:         YES
--       codec:             NO
--       format:            NO
--       util:                  NO
--       swscale:          NO

Then if i still try to use make i get:

Linking CXX shared library ../../lib/libopencv_photo.so
In file included from /home/ubuntu/test_lambda/rb-opencv/modules/highgui/src/cap_ffmpeg.cpp:45:0:
/home/ubuntu/test_lambda/rb-opencv/modules/highgui/src/cap_ffmpeg_impl.hpp:71:6: error: #error "libswscale is necessary to build the newer OpenCV ffmpeg wrapper"

OpenCV can’t find my libavcodec etc… and I have no clue how to fix that. I don’t understand why it can’t find with all the steps I have done before. Any ideas? Thanks for your help.

About this issue

Original URL
State: closed
Created 8 years ago
Comments: 28 (13 by maintainers)

Most upvoted comments

Just to add a solution because i ran throught the same problem of libswscale not being detected whereas it was installed on its latest version.

Problem is that cmake use pkg-config to check for modules presents and pkg-config does not know of all the package present in your system but only those which were compiled with pkg-config flags

cc pkg-config --cflags --libs x -o myapp myapp.c (sorry for bad markdown but there are actually backquotes that surround pkg-config --cflags --libs x

from freedesktop page

when typing pkg-config --list-allno libswscale was showing up. But you can easily add packages or libraries already present in your system to pkg-config. You just have to create a file called <package_name>.pc in /usr/share/pkgconfig/ directory and fill it with correct fields.

So to add libswscale to pkg-config list, just do the following

create /usr/share/pkgconfig/libswscale.pc
edit file. Should look like

Name: libswscale
Description: libswscale
Version: 300
libswscaledir=/usr/lib/x86_64-lniux-gnu/libswscale.so

cmake -D CMAKE_BUILD_TYPE=Release -D CMAKE_INSTALL_PREFIX=/usr/local …

it should now compile with ffmpeg support.

ClementViel on Aug 29, 2016

Thanks for opening up this issue. I have the same problem and due to academic stuffs, I need to stay with 2.4.11. So how do I build it on this version without moving on to OpenCV 3? (My project won’t involve video at all)

Thanks.

AbramTTP on Apr 6, 2016

I fixed the problem with OpenCV 3. you were right about not using the cake UI! Some flags were wrong.

PYTHON2_INCLUDE_DIR should be PYTHON2_INCLUDE_PATH and PYTHON2_LIBRARY should be -PYTHON2_LIBRARIES.

I’ve built opencv 3 without ffmpeg see if i can use the new motion jpeg codec but it can’t open a video capture.

corentin87 on Jan 13, 2016