[Mp4-tech] UMV in MPEG-4

[Mukul C]

Hi friends,
I have a query regarding the Unlimited Motion Vector (UMV see clause
7.6.4in the standard) in the
MPEG-4 standard for Simple Profile .
For normal files whose vop_width and vop_height is a multiple of 16 ,the
reference frame area is vop_width x vop_height and if the motion vector
points outside this area (UMV) then we have to pass the nearest pixel .This
can be implemented by padding the frame all around with the last pel data.
But what I am not sure about is that what is the reference frame area for
files whose vop_width or vop_height is not a multiple of 16.In such a case
what is the reference frame area ? Is it still vop_width x vop_height or is
it vop_width x vop_height where both are the nearest multiples of 16 ?We
will have to pad differently in these 2 cases - what I want to know is which
interpretation is correct ?
For example if we have a file of size 176 x 138 then is the ref frame area
176 x 138 ( we will have to pad from 139th row onwards) or is the ref frame
area 176 x 144( we will now have to pad after the 144 th row) ?
Regards,
Mukul.
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