The build script is to be fixed.
Right now it assumes that 32-bit MinGW is in the system path and
64-bit mingw is installed to c:\Apps\MinGW64.
It is important that gcc is used, not g++!
Otherwise the produced DLL will likely be dependent on libgcc_s_dw2-1.dll or similar DLL.
While we want to make the DLLs with minimum dependencies: Win32 libraries + msvcrt.dll.
ffopencv.c is really a C++ source, hence -x c++ is used.
How to update opencv_ffmpeg.dll and opencv_ffmpeg_64.dll when a new version of FFMPEG is release?
1. Install 32-bit MinGW + MSYS from
http://sourceforge.net/projects/mingw/files/Automated%20MinGW%20Installer/mingw-get-inst/
Let's assume, it's installed in C:\MSYS32.
2. Install 64-bit MinGW. http://mingw-w64.sourceforge.net/
Let's assume, it's installed in C:\MSYS64
3. Copy C:\MSYS32\msys to C:\MSYS64\msys. Edit C:\MSYS64\msys\etc\fstab, change C:\MSYS32 to C:\MSYS64.
4. Now you have working MSYS32 and MSYS64 environments.
Launch, one by one, C:\MSYS32\msys\msys.bat and C:\MSYS64\msys\msys.bat to create your home directories.
4. Download ffmpeg-x.y.z.tar.gz (where x.y.z denotes the actual ffmpeg version).
Copy it to C:\MSYS{32|64}\msys\home\<loginname> directory.
5. To build 32-bit ffmpeg libraries, run C:\MSYS32\msys\msys.bat and type the following commands:
5.1. tar -xzf ffmpeg-x.y.z.tar.gz
5.2. mkdir build
5.3. cd build
5.4. ../ffmpeg-x.y.z/configure --enable-w32threads
5.5. make
5.6. make install
5.7. cd /local/lib
5.8. strip -g *.a
6. Then repeat the same for 64-bit case. The output libs: libavcodec.a etc. need to be renamed to libavcodec64.a etc.
7. Then, copy all those libs to <opencv>\3rdparty\lib\, copy the headers to <opencv>\3rdparty\include\ffmpeg_.
8. Then, go to <opencv>\3rdparty\ffmpeg, edit make.bat
(change paths to the actual paths to your msys32 and msys64 distributions) and then run make.bat
