System information (version)

• OpenCV => 3.4
• Operating System / Platform => Windows 10
• Compiler => Visual Studio 15 2017

Detailed description

FFmpeg can be natively compiled using MSVC and MSYS. However, OpenCV does not allow FFmpeg to be used directly as under Linux. Instead, it requires the opencv_ffmpeg*.dll wrappers to be built first. These wrappers are also downloaded and used unconditionally under Windows.

Steps to reproduce

• Compile FFmpeg using the MSVC toolchain
• Configure OpenCV with previously compiled and installed FFmpeg in CMAKE_PREFIX_PATH

OpenCV will not use the compiled FFmpeg package. Instead, it will download prebuilt binaries.