[M4IF Technotes] MV in P in interlaced VOP

[Tania Orenshtein]

Hi,
I have a question about motion vectors calculation for P- and S(GMC)in
interlaced VOP.
As I understand a frame predicted macroblock can be in the 4MV mode.
If so, chroma MV is calculated by averaging for Y MV.
On the other side, the first sentence in 7.7.2.1 (P. 225) says
"For each component of motion vector in P- and S(GMC)-VOPs, the median value
of the candidate predictor vectors for the same component is computed ..."
So how is MV for chroma calculated for the frame predicted MB in 4MV?
Best regards,
Tania