[Tracker] hw codec suport issues in tracker-extract-gstreamer

["Chen, Zhenqiang" <zhenqiang chen intel com>]

Hi All, 
 
Currently tracker-extract-gstreamer uses "decodebin2" to extract the metadata.
It does not suport hw codec like mp4. 

"decodebin2" does not take "video/x-va" as a valid type.
But "playbin2" can play the mp4 file. 

How to support the hw codec in tracker?

 
Thanks!
-Zhenqiang