编译Opencv和FFmpeg
1 安装ffmpeg¶
1.1 下载ffmpeg¶
下班ffmpeg小于4.4版本，这里下载ffmpeg 4.1版本。
1.2 编译ffmpeg¶
编译的bin、so等文件，就放在ffmpeg源码根目录。
cd ffmpeg
./configure --enable-shared --disable-x86asm --libdir=. --prefix=. --disable-static
make -j8
make install
mkdir ffmpeg-4.1
cd ffmpeg-4.1 && mkdir lib && cd ..
mv lib*.so* ffmpeg-4.1/lib
mv bin ffmpeg-4.1/
mv include ffmpeg-4.1/
mv share ffmpeg-4.1/
mv pkgconfig ffmpeg-4.1/lib/
$ ls ffmpeg-4.1
bin ffmpeg-config.cmake FfmpegConfig.cmake include lib share
1.3 编写ffmpeg-config.cmake文件¶
编写ffmpeg-config.cmake文件是为了让opencv编译时，正确的找到这个ffmpeg的位置。FfmpegConfig.cmake文件的内容和ffmpeg-config.cmake文件相同。命名规则安装cmake find_package的命令方式。
set(ffmpeg_path "${CMAKE_CURRENT_LIST_DIR}")
message("ffmpeg_path: ${ffmpeg_path}")
set(FFMPEG_EXEC_DIR "${ffmpeg_path}/bin")
set(FFMPEG_LIBDIR "${ffmpeg_path}/lib")
set(FFMPEG_INCLUDE_DIRS "${ffmpeg_path}/include")
# library names
set(FFMPEG_LIBRARIES
${FFMPEG_LIBDIR}/libavformat.so
${FFMPEG_LIBDIR}/libavdevice.so
${FFMPEG_LIBDIR}/libavcodec.so
${FFMPEG_LIBDIR}/libavutil.so
${FFMPEG_LIBDIR}/libswscale.so
${FFMPEG_LIBDIR}/libswresample.so
${FFMPEG_LIBDIR}/libavfilter.so
)
# found status
set(FFMPEG_libavformat_FOUND TRUE)
set(FFMPEG_libavdevice_FOUND TRUE)
set(FFMPEG_libavcodec_FOUND TRUE)
set(FFMPEG_libavutil_FOUND TRUE)
set(FFMPEG_libswscale_FOUND TRUE)
set(FFMPEG_libswresample_FOUND TRUE)
set(FFMPEG_libavfilter_FOUND TRUE)
# library versions, 注意这几个变量，一定要设置为全局CACHE变量
set(FFMPEG_libavutil_VERSION 56.31.100 CACHE INTERNAL "FFMPEG_libavutil_VERSION") # info
set(FFMPEG_libavcodec_VERSION 58.54.100 CACHE INTERNAL "FFMPEG_libavcodec_VERSION") # info
set(FFMPEG_libavformat_VERSION 58.29.100 CACHE INTERNAL "FFMPEG_libavformat_VERSION") # info
set(FFMPEG_libavdevice_VERSION 58.8.100 CACHE INTERNAL "FFMPEG_libavdevice_VERSION") # info
set(FFMPEG_libavfilter_VERSION 7.57.100 CACHE INTERNAL "FFMPEG_libavfilter_VERSION") # info
set(FFMPEG_libswscale_VERSION 5.5.100 CACHE INTERNAL "FFMPEG_libswscale_VERSION") # info
set(FFMPEG_libswresample_VERSION 3.5.100 CACHE INTERNAL "FFMPEG_libswresample_VERSION") # info
set(FFMPEG_FOUND TRUE)
set(FFMPEG_LIBS ${FFMPEG_LIBRARIES})
status(" #################################### FFMPEG:" FFMPEG_FOUND THEN "YES (find_package)" ELSE "NO (find_package)")
status(" avcodec:" FFMPEG_libavcodec_VERSION THEN "YES (${FFMPEG_libavcodec_VERSION})" ELSE NO)
status(" avformat:" FFMPEG_libavformat_VERSION THEN "YES (${FFMPEG_libavformat_VERSION})" ELSE NO)
status(" avutil:" FFMPEG_libavutil_VERSION THEN "YES (${FFMPEG_libavutil_VERSION})" ELSE NO)
status(" swscale:" FFMPEG_libswscale_VERSION THEN "YES (${FFMPEG_libswscale_VERSION})" ELSE NO)
status(" avresample:" FFMPEG_libavresample_VERSION THEN "YES (${FFMPEG_libavresample_VERSION})" ELSE NO)
2 安装Opencv¶
2.1 编译opencv¶
编写build_with_ffmpeg4-1.sh文件，编译opencv
#!/bin/bash
OPENCV_INSTALL_DIR=`pwd`/opencv_install
mkdir -p ${OPENCV_INSTALL_DIR}
FFMPEG_FIND_DIR=`pwd`/compile_opencv/ffmpeg-4.1/ffmpeg-4.1/
BUILD_DIR=build_ffmpeg4.1
mkdir ${BUILD_DIR}
cd ${BUILD_DIR} || return
pwd
cmake .. \
-D CMAKE_BUILD_TYPE=Release \
-D CMAKE_INSTALL_PREFIX=${OPENCV_INSTALL_DIR} \
-D BUILD_TESTS=OFF \
-D BUILD_PERF_TESTS=OFF \
-D WITH_CUDA=OFF \
-D WITH_VTK=OFF \
-D WITH_MATLAB=OFF \
-D BUILD_DOCS=OFF \
-D BUILD_opencv_python3=OFF \
-D BUILD_opencv_python2=OFF \
-D WITH_IPP=OFF \
-D BUILD_SHARED_LIBS=ON \
-D BUILD_opencv_apps=OFF \
-D WITH_CUDA=OFF \
-D WITH_OPENCL=OFF \
-D WITH_VTK=OFF \
-D WITH_MATLAB=OFF \
-D BUILD_DOCS=OFF \
-D BUILD_opencv_python3=OFF \
-D BUILD_opencv_python2=OFF \
-D BUILD_JAVA=OFF \
-D BUILD_FAT_JAVA_LIB=OFF \
-D WITH_PROTOBUF=OFF \
-D WITH_QUIRC=OFF \
-D WITH_FFMPEG=ON \
-D OPENCV_GENERATE_PKGCONFIG=ON \
-D OPENCV_FFMPEG_USE_FIND_PACKAGE=ON \
-D OPENCV_FFMPEG_SKIP_BUILD_CHECK=ON \
-D FFMPEG_DIR=${FFMPEG_FIND_DIR}
make -j8
make install
编译opencv，编译好的文件会安装到当前目录下的opencv_install。
bash ./build_with_ffmpeg4.2.2_osx.sh
在编译时可以先把make和make install注释了，查看opencv编译时，FFmpeg是否是YES状态。在运行时，也可以通过代码检测FFmpeg状态。
std::cout << cv::getBuildInformation();
3 打包ffmpeg和opencv作为第三方库¶
现在将编译好的ffmpeg和opencv放在同一个目录下，作为第三方库给其他主机使用。
3.1 创建3rd_party¶
$ mkdir 3rd_party
$ mv ffmpeg-4.1 3rd_party
$ mv opencv_install/ 3rd_party/opencv4.5.5
$ ls
ffmpeg-4.1 opencv-4.5.5
3.2 使用ffmpeg和opencv¶
现在假设一个项目名叫ProjA，那么将3rd_party复制到ProjA根目录，然后创建一个build.sh。为了避免找到主机上的其他ffmpeg，需要设置LD_LIBRARY_PATH，将${FFMPEG_LIB_DIR}加入进去。
#!/bin/bash
current_dir=$(cd `dirname $0`; pwd)
export OPENCV_LIB_DIR=`pwd`/3rd_party/opencv-4.5.5/lib64/cmake/opencv4;
FFMPEG_LIB_DIR=`pwd`/3rd_party/ffmpeg-4.1/lib;
GCC_VERSION="8.2"
export CC=/opt/compiler/gcc-${GCC_VERSION}/bin/gcc
export CXX=/opt/compiler/gcc-${GCC_VERSION}/bin/g++
export PATH=/opt/compiler/gcc-${GCC_VERSION}/bin${PATH:+:${PATH}}
export LD_LIBRARY_PATH=/opt/compiler/gcc-${GCC_VERSION}/lib:${FFMPEG_LIB_DIR}${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}
export PKG_CONFIG_PATH=/opt/compiler/gcc-${GCC_VERSION}/lib/pkgconfig${PKG_CONFIG_PATH:+:${PKG_CONFIG_PATH}}
build_folder=${current_dir}/build
clean=$1
if [ -d ${build_folder} ]; then
if [ "${clean}" == "clean" ]; then
rm -rf ${build_folder}/*
fi
else
mkdir ${build_folder}
fi
cd ${build_folder} && cmake ..
make -j4
make install
exit $?
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