[Mp4-tech] Max. range of motion vectors

[Tourapis, Alexis]

Dear Pedro,
The vertical motion vector range is specified in Table A-1 of the
standard and depends on the level number used. Horizontal motion vector
range is [-2048,2047.75] regardless of level.
I am afraid that if you would like to use your own limits, then you
would have to modify the code. However, it is not very difficult. Just
look in the code how the above limits are used (i.e., search for
LEVELMVLIMIT), and extend the code to allow for explicit limits as well.
Let me know if you need any help.
Kind regards,
Alexis
-----Original Message-----
From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of
palexi iuma.ulpgc.es
Sent: Friday, July 14, 2023 1:35 PM
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech] Max. range of motion vectors
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.
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