• As a first step, you need to install the following dependencies:

  $ sudo apt install libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev gstreamer1.0-plugins-{base,good,bad}

• Secondly, you need to launch OpenCV cmake with an extra option specified:

  $ cmake /path-to-opencv -DOPENCV_GAPI_GSTREAMER=ON

After completing these steps, you should see the following in the cmake output:

-- Checkingfor module'gstreamer-base-1.0'--   Found gstreamer-base-1.0, version 1.16.3-- Checkingfor module'gstreamer-app-1.0'--   Found gstreamer-app-1.0, version 1.16.3-- Checkingfor module'gstreamer-riff-1.0'--   Found gstreamer-riff-1.0, version 1.16.3-- Checkingfor module'gstreamer-pbutils-1.0'--   Found gstreamer-pbutils-1.0, version 1.16.3-- Checkingfor module'gstreamer-video-1.0'--   Found gstreamer-video-1.0, version 1.16.3-- Checkingfor module'gstreamer-audio-1.0'--   Found gstreamer-audio-1.0, version 1.16.3

And, also the following:

--   Video I/O:--   ...--     GStreamer:                   YES (1.16.3)--   ...

When you build G-API with GStreamer support, tests for streaming via GStreamerSource are enabled. However, some of them require test data fromopencv_extra repository. So, to launch all the tests successfully, you need:

• Cloneopencv_extra repository:

  $ git clone https://github.com/opencv/opencv_extra.git

• SetOPENCV_TEST_DATA_PATH environment variable:

  $export OPENCV_TEST_DATA_PATH=/path-to-opencv_extra/testdata

• Run tests with*GStreamer* filter:

  $ ./path-to-opencv-bin/opencv_test_gapi --gtest_filter=*GStreamer*

After completing these steps, you should see that all of tests pass.For example:

You may, however, notice some warnings during execution, like these ones:

or

Please don't worry, they are expected!