For info, on Ubuntu 16.04 I tried the command:
sudo apt-get install libgstreamer-plugins-base
which returned:
Unable to locate package libgstreamer-plugins-base
The command:
sudo apt-get install libgstreamer0.10-dev libgstreamer-plugins-base0.10-dev libfreeimage3 libc6:i386
worked and allowed Pixinsight to run.
cheers,
Tom