[M4IF Technotes] MVD

[cloverleafland mail.hongkong.com]

Dear all,
when viewing the standard 14496-2, I get confused with the vlc for MVD. There mentioned to have a flag called vop_fcode_forward and vop_fcode_backward to mark the range of MVD, but from the Table B-12 and Table B-29, both mention the range of MVD to be coded in [-16, 16]. However, in the vop_focde_forward/backward, the rnage of motion vector would be upto range [-2048,2047]. Would anyone explain why would the case be like this?
Also, for the MVD, does it mean to be the motion vector difference with the motion vector of the one previous block just before the current block?
Also, in the Table B-12 and Table B-29, why there is two table for the same purpose? Which one should be used instead?
Thanks so much... 
Regards,
Clover  
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