【OpenCV】编译OpenCV时，FFmpeg或ippicv下载不成功的解决方案

在自己编译OpenCV时，因为种种原因可能会导致FFmpeg或ippicv下载不成功的问题，可以通过手动配置来解决这类问题，当然也可以直接配置之后再编译。

在进行配置之前，首先前往GitHub下载相应的库。

链接：opencv/opencv_3rdparty

链接打开之后页面内容大致如上图所示，图中圈出了ffmpeg和iipicv的不同版本，具体用哪一版就各取所需吧。明确版本之后点击相应的链接进入下载。

下载完成之后解压，位置不重要。

到此，准备完毕。

FFmpeg的配置

1. 将“..\opencv_3rdparty-ffmpeg-master_20160715\ffmpeg” 目录中的 ffmpeg_version.cmake、opencv_ffmpeg.dll、opencv_ffmpeg_64.dll 三项复制到 “path to your OpenCV\opencv\sources\3rdparty\ffmpeg” 目录下。
   
   将上图中的三项复制到下图的目录中
   

2. 编辑 ffmpeg.cmake
   在 “path to your OpenCV\opencv\sources\3rdparty\ffmpeg” 中打开文件 ffmpeg.cmake ，将其内容修改为：

   message(STATUS "FFMPEG: Package successfully downloaded")include(${CMAKE_CURRENT_LIST_DIR}/ffmpeg_version.cmake)

   保存内容。

到此，ffmpeg配置完毕。

ippicv的配置

1. 在前面下载解压的目录“..\opencv_3rdparty-ippicv-master_20151201\ippicv” 中将ippicv_windows_20151201.zip 解压到当前目录。
   
   在 “path to your OpenCV \opencv\sources\3rdparty\ippicv” 中创建文件夹unpack，将解压得到的ippicv_win 复制到新创建的unpack 中。
   

2. 编辑 downloader.cmake
   将downloader.cmake 的内容修改为：

## The script downloads ICV package## On return this will define:# OPENCV_ICV_PATH - path to unpacked downloaded package#function(_icv_downloader)  # Commit SHA in the opencv_3rdparty repo  set(IPPICV_BINARIES_COMMIT "81a676001ca8075ada498583e4166079e5744668")  # Define actual ICV versions  if(APPLE)    set(OPENCV_ICV_PACKAGE_NAME "ippicv_macosx_20151201.tgz")    set(OPENCV_ICV_PACKAGE_HASH "4ff1fde9a7cfdfe7250bfcd8334e0f2f")    set(OPENCV_ICV_PLATFORM "macosx")    set(OPENCV_ICV_PACKAGE_SUBDIR "/ippicv_osx")  elseif(UNIX)    if(ANDROID AND NOT (ANDROID_ABI STREQUAL x86 OR ANDROID_ABI STREQUAL x86_64))      return()    endif()    set(OPENCV_ICV_PACKAGE_NAME "ippicv_linux_20151201.tgz")    set(OPENCV_ICV_PACKAGE_HASH "808b791a6eac9ed78d32a7666804320e")    set(OPENCV_ICV_PLATFORM "linux")    set(OPENCV_ICV_PACKAGE_SUBDIR "/ippicv_lnx")  elseif(WIN32 AND NOT ARM)    set(OPENCV_ICV_PACKAGE_NAME "ippicv_windows_20151201.zip")    set(OPENCV_ICV_PACKAGE_HASH "04e81ce5d0e329c3fbc606ae32cad44d")    set(OPENCV_ICV_PLATFORM "windows")    set(OPENCV_ICV_PACKAGE_SUBDIR "/ippicv_win")  else()    return() # Not supported  endif()  set(OPENCV_ICV_UNPACK_PATH "${CMAKE_CURRENT_LIST_DIR}/unpack")  set(OPENCV_ICV_PATH "${OPENCV_ICV_UNPACK_PATH}${OPENCV_ICV_PACKAGE_SUBDIR}")  message(STATUS "ICV: Package successfully downloaded")  set(OPENCV_ICV_PATH "${OPENCV_ICV_PATH}" PARENT_SCOPE)endfunction()_icv_downloader()

保存内容。
到此，ippicv配置完毕。

开始快乐的编译OpenCV吧！