ubuntu 14.04 编译opencv-3.4.2 报错解决：
错误信息：
/usr/bin/ld: /usr/local/lib/libavformat.a(allformats.o): relocation R_X86_64_32 against `.bss' can not be used when making a shared object; recompile with -fPIC
/usr/local/lib/libavformat.a: error adding symbols: 错误的值
collect2: error: ld returned 1 exit status
make[2]: *** [lib/libopencv_videoio.so.3.4.2] 错误 1
make[1]: *** [modules/videoio/CMakeFiles/opencv_videoio.dir/all] 错误 2
make[1]: *** 正在等待未完成的任务....
原因：ffmpeg未安装或配置不对
解决办法：
1 重新配置编译ffmpeg
2 重新配置编译opencv
******* 参考操作步骤: https://blog.csdn.net/linuxsmallping/article/details/82968501