System Environment:
--------------------------

--Platform: 945G


--2D driver:
commit 548d4c0f979a72eac5d0c9c76da12f0bd05e64e1 

--3D driver:
commit 990e010394a2685c1daeaef61cf4f7e2a0ba419e

--Xserver:
commit cf20df39cc78203d17b99223908af388ecbf7d0e 

--Drm
commit b44f2da380e78769b58c751e81f376f0fa1f48aa 

--Kernel:
2.6.23.1


Bug detailed description:
-------------------------
when coded_block_pattern is set to '1111b', and only pass the Y component, the rendering is not correct


Reproduce steps:
----------------
1. enable XvMC in xorg.conf
2. start X
3. compile and run attached case


Current result:
----------------
code_block_pattern not working well


Expected result:
----------------
code_block_pattern should work well