This format introduces an extra level of indirection in the process of accessing YUV pixels in the surface. Locking the DirectDraw or DCI CLPL surface returns a pointer which itself points to three other pointers. These pointers respectively point to an NxN Y plane, an (N/2)x(N/2) U plane and an (N/2)x(N/2) V plane. The Y plane pointer retrieved is (allegedly) valid even when the surface is subsequently unlocked but the U and V pointers can only be used with a lock held (as you should be doing anyway if adhereing to the DirectDraw/DCI spec).
| Horizontal | Vertical | |
| Y Sample Period | 1 | 1 |
| V Sample Period | 2 | 2 |
| U Sample Period | 2 | 2 |
Positive biHeight implies top-down image (top line first)
Based on: YV12