This is the exact error that I am getting. My OS is Ubuntu 16.10.
OpenCV Error: Unspecified error (The function is not implemented. Rebuild the library with
I followed this tutorial (OpenCV GTK+2.x error) and did the following. It worked for me :
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D WITH_TBB=ON -D BUILD_NEW_PYTHON_SUPPORT=ON -D WITH_V4L=ON -D INSTALL_C_EXAMPLES=ON -D INSTALL_PYTHON_EXAMPLES=ON -D BUILD_EXAMPLES=ON -D WITH_QT=ON -D WITH_GTK=ON -D WITH_OPENGL=ON ..