1.安装时遇到的第一个问题

上问题代码：

/usr/bin/ld: warning: libopencv_core.so.2.4, needed by //usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5, not found (try using -rpath or -rpath-link)
/usr/bin/ld: warning: libopencv_imgproc.so.2.4, needed by //usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5, not found (try using -rpath or -rpath-link)
//usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5: undefined reference to `cvSmooth'
//usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5: undefined reference to `cvErode'
//usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5: undefined reference to `cvReleaseStructuringElement'
//usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5: undefined reference to `cvCreateStructuringElementEx'
//usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5: undefined reference to `cvCreateImageHeader'
//usr/lib/x86_64-linux-gnu/libavfilter-ffmpeg.so.5: undefined reference to `cvDilate'
collect2: error: ld returned 1 exit status
tools/VideoViewer/CMakeFiles/VideoViewer.dir/build.make:122: recipe for target 'tools/VideoViewer/VideoViewer' failed
make[2]: *** [tools/VideoViewer/VideoViewer] Error 1
CMakeFiles/Makefile2:289: recipe for target 'tools/VideoViewer/CMakeFiles/VideoViewer.dir/all' failed
make[1]: *** [tools/VideoViewer/CMakeFiles/VideoViewer.dir/all] Error 2
Makefile:149: recipe for target 'all' failed
make: *** [all] Error 2

各位老铁也一定百度了不少，也看得懂这个问题出在哪
问题就处在ffmpeg不兼容，可能是版本原因

2. 解决方法

卸载ffmpeg

sudo apt-get purge ffmpeg

卸载后在官网上手动下载：http://ffmpeg.org/releases/ffmpeg-4.3.tar.xz
再解压、安装。

3.新的问题又来了

当再重新进入pangolin/bulid/中编译make时，又出现错误如下：

src/CMakeFiles/pangolin.dir/build.make:662: recipe for target 'src/CMakeFiles/pangolin.dir/video/video_output.cpp.o' failed
make[2]: *** [src/CMakeFiles/pangolin.dir/video/video_output.cpp.o] Error 1
make[2]: *** Waiting for unfinished jobs....
src/CMakeFiles/pangolin.dir/build.make:638: recipe for target 'src/CMakeFiles/pangolin.dir/video/video.cpp.o' failed
make[2]: *** [src/CMakeFiles/pangolin.dir/video/video.cpp.o] Error 1
CMakeFiles/Makefile2:135: recipe for target 'src/CMakeFiles/pangolin.dir/all' failed
make[1]: *** [src/CMakeFiles/pangolin.dir/all] Error 2
Makefile:127: recipe for target 'all' failed
make: *** [all] Error 2

还是找啊找
最后还是看到博客：Ubuntu 14.04下安装Pagolin遇到的问题及解决方法（之一）中的方法才成功安装。

4.终结方法

到Pagolin/src文件夹下，在CMakeList.txt中删去下面这段代码（屏蔽掉ffmpeg的影响）：

    find_package(FFMPEG QUIET)
    if(BUILD_PANGOLIN_VIDEO AND FFMPEG_FOUND)
      set(HAVE_FFMPEG 1)
      list(APPEND INTERNAL_INC  ${FFMPEG_INCLUDE_DIRS} )
      list(APPEND LINK_LIBS ${FFMPEG_LIBRARIES} )
      list(APPEND HEADERS ${INCDIR}/video/drivers/ffmpeg.h)
      list(APPEND SOURCES video/drivers/ffmpeg.cpp)
      list(APPEND VIDEO_FACTORY_REG RegisterFfmpegVideoFactory )
      list(APPEND VIDEO_FACTORY_REG RegisterFfmpegVideoOutputFactory )
     
      if(_GCC_)
        # FFMPEG is a real pain for deprecating the API.
        set_source_files_properties(video/drivers/ffmpeg.cpp    PROPERTIES COMPILE_FLAGS "-Wno-deprecated-declarations")
      endif()
      message(STATUS "ffmpeg Found and Enabled")
    endif()

【可能原因】ffmpeg库和Pagolin版本之间可能存在冲突。本文的解决办法，以及其他可能的解决方法（如修改Pagolin的部分代码）和原因请参见下面这个帖子：

https://github.com/stevenlovegrove/Pangolin/issues/27