[M4IF Technotes] 'vop_coded' for enhancement layers

[Shanableh Tamer-BTS027]

Hi,
I am having a bit of difficulty understanding the 'vop_coded' field for the enhancement layers. In the case of Simple Profile the immediately preceding VOP is copied, provided that its vop_coded=1.
But what about the enhancement layer of the Simple Scalable Profile, how do I interpret "preceding VOP"? is it the forward reference VOP? is it the preceding VOP in the same layer?
I would appreciate your views and explanations on this, thanks
Tamer