gstreamer1.0-libav software package provides libav plugin for GStreamer, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gstreamer1.0-libav
gstreamer1.0-libav is installed in your system.
Make ensure the gstreamer1.0-libav package were installed using the commands given below,
$ sudo dpkg-query -l | grep gstreamer1.0-libav *
You will get with gstreamer1.0-libav package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Libraries |
| Package | gstreamer1.0-libav |
| Version | 1.8.0-1 |
| Description | libav plugin for GStreamer |
| Sub Section | Libs |