CMake编译OpenCV3.4.6时opencv_ffmpeg.dll等下载失败的解决办法

悠悠 2023-07-06 14:58 3阅读 0赞

报错信息如下：

FFMPEG: Download: opencv_ffmpeg.dll
    CMake Warning at cmake/OpenCVDownload.cmake:193 (message):
      FFMPEG: Download failed: 35;"SSL connect error"
    
      For details please refer to the download log file:
    
      D:/opencv/opencv346/contrib_build/CMakeDownloadLog.txt
    
    Call Stack (most recent call first):
      3rdparty/ffmpeg/ffmpeg.cmake:20 (ocv_download)
      cmake/OpenCVFindLibsVideo.cmake:228 (download_win_ffmpeg)
      CMakeLists.txt:793 (include)

提示FFMPEG下载失败，因为无法连接到服务器，打开 CMakeDownloadLog.txt 查看详细信息。

查看CMakeDownloadLog.txt：

#use_cache "D:/opencv/opencv346/sources/.cache"
    #do_copy "opencv_ffmpeg.dll""41b81bb9a50cabd4bea385f7b50a069a" "https://raw.githubusercontent.com/opencv/opencv_3rdparty/fe71c0ad807fdc33c2178e48e488f1e9b177c39a/ffmpeg/opencv_ffmpeg.dll""D:/opencv/opencv346/contrib_build/3rdparty/ffmpeg"
    这里的意思是说将 opencv_ffmpeg.dll（它的md5签名是 41b81bb9a50cabd4bea385f7b50a069a，下载地址是  "https://raw.githubusercontent.com/opencv/opencv_3rdparty/fe71c0ad807fdc33c2178e48e488f1e9b177c39a/ffmpeg/opencv_ffmpeg.dll" ）
     从 "D:/opencv/opencv346/sources/.cache" 拷贝到 "D:/opencv/opencv346/contrib_build/3rdparty/ffmpeg"目录下。
     
    #missing "D:/opencv/opencv346/contrib_build/3rdparty/ffmpeg/opencv_ffmpeg.dll"
    #check_md5 "D:/opencv/opencv346/sources/.cache/ffmpeg/41b81bb9a50cabd4bea385f7b50a069a-opencv_ffmpeg.dll"
    #mismatch_md5 "D:/opencv/opencv346/sources/.cache/ffmpeg/41b81bb9a50cabd4bea385f7b50a069a-opencv_ffmpeg.dll" "d41d8cd98f00b204e9800998ecf8427e"
    #delete "D:/opencv/opencv346/sources/.cache/ffmpeg/41b81bb9a50cabd4bea385f7b50a069a-opencv_ffmpeg.dll"
    意思是目标目录下没有此文件
    
    #cmake_download "D:/opencv/opencv346/sources/.cache/ffmpeg/41b81bb9a50cabd4bea385f7b50a069a-opencv_ffmpeg.dll" 
    "https://raw.githubusercontent.com/opencv/opencv_3rdparty/fe71c0ad807fdc33c2178e48e488f1e9b177c39a/ffmpeg/opencv_ffmpeg.dll"
    意思是准备cmake下载此文件到源代码路径 /.cache/ffmpeg/，并命名为"md5-文件名"
    
    # timeout on name lookup is not supported
    # Trying 151.101.228.133:443...
    # TCP_NODELAY set
    # Connected to raw.githubusercontent.com (151.101.228.133) port 443 (#0)
    # schannel: ALPN, offering http/1.1
    # schannel: failed to receive handshake, SSL/TLS connection failed
    # Closing connection 0
    # schannel: shutting down SSL/TLS connection with raw.githubusercontent.com port 443
    # Send failure: Connection was reset
    # schannel: failed to send close msg: Failed sending data to the peer (bytes written: -1)
    # 
    意思是连接到服务器超时失败

因为无法访问外网，自然就无法连接到下载服务器。那就直接通过外网下载好需要的文件，然后重命名为"md5-文件名"，放在 /.cache/ffmpeg/ 文件夹下面，或者直接放到目标路径 /3rdparty/ffmpeg/opencv\_ffmpeg.dll（不用重命名）。

注意：

1.https://raw.githubusercontent.com/opencv/opencv\_3rdparty/fe71c0ad807fdc33c2178e48e488f1e9b177c39a/ffmpeg/ffmpeg\_version.cmake 无法直接下载，

而是直接打开了ffmpeg\_version.cmake，可以右键网页选择另存为 ffmpeg\_version.cmake.txt，然后再改为ffmpeg\_version.cmake。这里如果自己新建一个txt，然后直接将网页上的内容拷进去，然后再该后缀为.cmake是不行的，会提示md5不匹配。

2.不同版本的OpenCV对应的 opencv\_ffmpeg.dll 等缺失文件的 md5 签名是不一样的