OpenCV3.4.1-contrib 编译 过程中经常下载失败的文件，包括ippicv_2017u3_win_intel64_general_20170822.zip； opencv_ffmpeg.dll opencv_ffmpeg_64.dll vgg_generated_48.i vgg_generated_64.i ffmpeg_version.cmake 。。。。。。等

Cmake编译opencv卡在Download: opencv_ffmpeg.dll ----------------------------------------------------------------------------- Cmake编译Opencv时因为网络问题ffmpeg、ippicv等内容可能会下载失败导致编译不完全。 ----------------------------------------------------------------------------

CMake opencv时Download: opencv_ffmpeg.dll、ippicv等失败的解决方法，自己手动下载 提供文件（OpenCV 3.4.0），原因参考[https://blog.csdn.net/KayChanGEEK/article/details/79919417](https://blog.csdn.net/KayChanGEEK/article/details/79919417)

cmake 编译opencv 缺失opencv_ffmpeg.dll 、 opencv_ffmpeg_64.dll、ffmpeg_version.cmake等问题，只需替换下载替换.cache目录即可 ： opencv-4.5.0\.cache