Clarifications about Gstreamer
Solution 1:
Gstreamer 1.0 is installed by default on 14.04 (See the desktop image manifest)
But you need to install additional plugins to get VA-API support.
Install the following package in a Terminal:
sudo apt-get install gstreamer1.0-vaapi
For VDPAU, check this answer: How to enable VDPAU on GStreamer?