Configure and Build OpenCV to Custom FFMPEG Install

Question

I cannot seem to configure OpenCV to link to a non-/usr/lib set of FFMPEG libraries.

My LD_LIBRARY_PATH contains a direct link to the folder for the custom

Answer 1

For OpenCV 3.x and ffmpeg 3.x, I have to apply the following patch

diff --git a/cmake/OpenCVFindLibsVideo.cmake b/cmake/OpenCVFindLibsVideo.cmake
index 13b62ac..bab9df3 100644
--- a/cmake/OpenCVFindLibsVideo.cmake
+++ b/cmake/OpenCVFindLibsVideo.cmake
@@ -228,6 +228,12 @@ if(WITH_FFMPEG)
     if(FFMPEG_libavresample_FOUND)
       ocv_append_build_options(FFMPEG FFMPEG_libavresample)
     endif()
+   CHECK_MODULE(libavcodec HAVE_FFMPEG)
+   CHECK_MODULE(libavformat HAVE_FFMPEG)
+   CHECK_MODULE(libavutil HAVE_FFMPEG)
+   CHECK_MODULE(libswscale HAVE_FFMPEG)
+   CHECK_MODULE(libswresample HAVE_FFMPEG)
+   CHECK_MODULE(libavresample HAVE_FFMPEG)
     if(HAVE_FFMPEG)
       try_compile(__VALID_FFMPEG
           "${OpenCV_BINARY_DIR}"

And with the following script to build

#!/bin/bash

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/Applications/ffmpeg/lib
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$HOME/Applications/ffmpeg/lib/pkgconfig
export PKG_CONFIG_LIBDIR=$PKG_CONFIG_LIBDIR:$HOME/Applications/ffmpeg/lib

cmake \
    -D BUILD_EXAMPLES=ON \
    -D BUILD_TESTS=OFF \
    -D OPENCV_EXTRA_EXE_LINKER_FLAGS="-Wl,-rpath,$HOME/Applications/ffmpeg/lib" \
    -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=$HOME/Applications/opencv \
    /path/to/opencv

Also, when build ffmpeg, I have to enable flags --enable-avresample.