源碼安裝支持ffmpeg的opencv2

1.首先安裝ffmpeg

　　apt-get install ffmpeg

2.安裝opencv對ffmeg的依賴

　#  for Compiling OpenCV with ffmpeg support
    　　apt-get install build-essential
    　　apt-get install cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev
    　　apt-get install python-dev python-numpy libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libjasper-dev libdc1394-22-dev
    　From <https://docs.opencv.org/3.4.2/d7/d9f/tutorial_linux_install.html>

3.下載opencv源碼並編譯

　>> cd ~/<my_working_directory>
    >> git clone https://github.com/opencv/opencv.git
    >> cd opencv
    >> git checkout 3.1.0
    >> cd ..
    >> git clone https://github.com/opencv/opencv_contrib.git
    >> cd opencv_contrib
    >> git checkout 3.1.0
    
    >> cd ~/<my_working_directory>/opencv
    >> mkdir build
    >> cd build
    
    >> cmake -D WITH_CUDA=OFF \
            -D CMAKE_BUILD_TYPE=Release \
            -D CMAKE_INSTALL_PREFIX=/usr/local \
            -D WITH_IPP=OFF \
            -D WITH_FFMPEG=ON  \
            -D OPENCV_EXTRA_MODULES_PATH=../../opencv_contrib/modules \
            -D BUILD_TESTS=OFF \
            -D BUILD_PERF_TESTS=OFF \
            -D INSTALL_PYTHON_EXAMPLES=OFF \
            -D INSTALL_C_EXAMPLES=OFF \
            -D PYTHON_EXECUTABLE=$(which python) \
            -D BUILD_EXAMPLES=OFF ..
    
    >> make -j$nproc
    >> make install