gstreamer-qapt software package provides GStreamer plugin to install codecs using QApt, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gstreamer-qapt
gstreamer-qapt is installed in your system.
Make ensure the gstreamer-qapt package were installed using the commands given below,
$ sudo dpkg-query -l | grep gstreamer-qapt *
You will get with gstreamer-qapt package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | KDE |
| Package | gstreamer-qapt |
| Version | 3.0.2-1+b2 [mips], 3.0.2-1+b1 |
| Description | GStreamer plugin to install codecs using QApt |
| Sub Section | KDE |