I noticed this while reading the code, and it seems wrong to me. From the documentation, gst_init_check "will return FALSE if GStreamer could not be initialized for some reason".

I do not understand why the current code ever works, because in my test project (with gstreamer 1.16.2), err is never NULL after a call to gst_init_check(NULL, NULL, &err);. But I could imagine that it is different with other versions of gstreamer.

I haven't tested my patch at all, but it seemed important enough to open a discussion, and a PR seemed like a good way. Feel free to close if I am missing something 😇.

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
• The PR is proposed to proper branch
• There is reference to original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake

build_image:Custom=gstreamer:14.04
buildworker:Custom=linux-4