How to have OpenCV built process use self-built ffmpeg?

[cudawarped]

@nji9

It would be nice if somebody would check if/ how these env var do have an effect at all.
Maybe a bug/ lack in documenation?

@crackwitz has already raised an issue to this effect.

Documentation for OPENCV_FFMPEG_WRITER_OPTIONS and OPENCV_FFMPEG_CAPTURE_OPTIONS

If it was me I would check that the env var is being passed correctly to OpenCV either by placing a breakpoint

opencv/opencv/blob/a478757483c644666ad36219db0aa81550abefc8/modules/videoio/src/cap_ffmpeg_impl.hpp#L3076C29-L3076C57

or increasing the log level

    OPENCV_FFMPEG_DEBUG=1
    OPENCV_LOG_LEVEL=DEBUG

I would also double check that OpenCV is using the supplied version of FFMpeg, not the automaitically downloaded OpenCV shared library and that calling that version outside of OpenCV (ffmpeg.exe) with the arguments you mention has the desired result.