phonon4qt5-backend-gstreamer from openSUSE:Backports:SLE-12-SP2 project
Select Your Operating System
Add repository and install manually
For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/openSUSE:Backports:SLE-12-SP2/standard/openSUSE:Backports:SLE-12-SP2.repo zypper refresh zypper install phonon4qt5-backend-gstreamer