gstreamer1.0-vaapi software package provides VA-API plugins for GStreamer, 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 gstreamer1.0-vaapi
gstreamer1.0-vaapi is installed in your system.
Make ensure the gstreamer1.0-vaapi package were installed using the commands given below,
$ sudo dpkg-query -l | grep gstreamer1.0-vaapi *
You will get with gstreamer1.0-vaapi package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Libraries |
| Package | gstreamer1.0-vaapi |
| Version | 1.8.3-1 |
| Description | VA-API plugins for GStreamer |
| Sub Section | Libs |