Your GStreamer installation is missing a plug-in. (By Pitivi Video Editor)

I am running Trisquel 7.0 LTS While Render from Pitivi, I get following error message:

Text is:

Sorry, something didn’t work right.

An error occured while trying to render your project. You might want to check our troubleshooting guide or file a bug report. See the details below for some basic information that may help identify the problem.

Details:

Your GStreamer installation is missing a plug-in.

gstdecodebin2.c(3928): gst_decode_bin_expose (): /pitivi+utils+pipeline+Pipeline:pitivi+utils+pipeline+pipeline1/GESTimeline:gestimeline1/GESVideoTrack:gesvideotrack1/GnlComposition:gnlcomposition2/GnlSource:gnlsource0/GstBin:videosrcbin/GstURIDecodeBin:uridecodebin1/GstDecodeBin:decodebin20:
no suitable plugins found

So, What plug-in(s) are missing? & How can I install missing plug-in?

Further Information:
$ dpkg -s gstreamer0.10-plugins-ugly | head
Package: gstreamer0.10-plugins-ugly
Status: install ok installed
Priority: optional
Section: libs
Installed-Size: 1259
Maintainer: Ubuntu Developers <name at domain>
Architecture: i386
Multi-Arch: same
Source: gst-plugins-ugly0.10
Version: 0.10.19-2ubuntu5