[M4IF Technotes] MVD=16 in MPEG4

[Herbert Thoma]

"Chen, Kenny" schrieb:
> 
> Hi,
> 
> In H.263, the table for MV difference ranges from -16 to 15.5, in MPEG4
> MVD=16 is added.
> But in VM18 there is :
>                 if (diff_vector < -range)
>                         diff_vector = diff_vector + 2*range;
>                 else if (diff_vector > range-1)
>                         diff_vector = diff_vector - 2*range;
> 
> range = 32;
> 
> from this equation, it seems we can not get MVD=16 from it, so why do MPEG4
> add MVD=16 in the vlc table? Is it useless?

Hi,
in MPEG-4 the range can be greater than +/-16, depending on the
fcode_forward/backward in the VOP header and then MVD=16 is
possible.
Yours,
 Herbert.
> thanks
> Ken
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Herbert Thoma
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