[M4IF Technotes] Rounding of motion vectors for chroma?

[Christoph Lampert]

Hi,
I have a question about rounding motion vectors, especially for 
chroma if quarterpel is active. I'll use a simple example.
Consider a macro block in inter4v mode with luminance motion vectors 
mv[0] to mv[3] in halfpel or quarterpel resolution. 
How do I calculate the motion vector for chroma from them? 
I know of course that it's  mv[0]+mv[1]+mv[2]+mv[3] / (2*4)
but how exactly is rounding supposed to be done? What I read from the
standard about this is as unclear as possible. 
Thank you in advance,
Christoph
-- 
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