Please give me advice about implementing gstreamer-vaapi

[1978dmzx at jcom.home.ne.jp]

Hello, 
 
I've troublled about playing the movie with gstreamer-vaapi plugin and Qt 
phonon for 4 weeks. 
 
I've added "video/x-vaapi-surface" to rawcaps definition in gst-plugins-base 
package. 
And when the movie file(mpeg4,rev2)was selected on qmediaplayer(this is Qt's 
demo program) , I've confirmed that "vaapidecode" was selected. but 
xvimagesink was selected instead of "vaapisink". 
 
Now I am planning to change the source code of "xvimagesink". if the 
contents of "xvimagesink" is "vaapisink" then the movie play normaly. 
Is this my idea right? 
Please advice me!! 
 
Best Regards, 
Hiroshi