[Mp4-tech] Max. range of motion vectors

[palexi iuma.ulpgc.es]

Hello,
I am testing a hardware design of the loop-filter. I am extracting the video
data directly from the reference design version 10.2, and I assumed that
motion vectors (mv), with a search area of 16, could take values between -128
and 127 (8 signed bits), but in a certain sequence (bridge-close.cif, from
http://trace.eas.asu.edu/yuv/cif.html), some mv reach values ranging from -255
to -188, ... (9 signed bits) in a no border block. I don't know if there is an
option that allow mv values going outside of the search area. Are those values
normal for mv? How can I limit these values to 8 signed
bits?
Regards
Pedro Alexi.