[Libva] copy decoded data back to CPU with help of opengl, is it possible?

[hank peng]

Hi:
My application want to get decoded data back using libva just like
VLC, but I found copy performance from GPU uncached cahe is very slow,
now I wonder if I can do this with help of opengl? My idea is like
this:
1. allocate a buffer that will store decoded data, bind it to opengl surface.
2. bind va decoded surface to opengl surface, is it available in libva-egl?
3. call opengl routine, let it copy data from the latter opengl
surface to former opengl surface.

I am new to opengl and libva, maybe my idea is wrong, correct me please!

-- 
The simplest is not all best but the best is surely the simplest!