[M4IF Technotes] Offscreen MVs

[Peter Haighton]

Graham,
If I understand you correctly, the values that you are mentioning are
coming from the reference frame. So by moving the block up by one pixel,
you would get
1
1
2
3
.
.
.
15
Peter
-----Original Message-----
From: technotes-admin   lists.m4if.org
[mailto:technotes-admin   lists.m4if.org]On Behalf Of the_ether
Sent: Monday, May 20, 2024 5:04 PM
To: Peter Haighton; technotes   lists.m4if.org
Subject: Re: [M4IF Technotes] Offscreen MVs
Thank you Peter.
> Yes, it is possible for a motion vector to point off the screen. The off
> screen pixels are duplicated from the edge of the on screen pixels.

Just so I'm absolutely sure I understand, in my example which edge is
filled?
If I start with the following feature at (0,0):
1     1    1....1
2     2    2....2
3     3    3....3
16 16 16 ...16
and if this feature moves up by one pixel so that the motion vector is
(0,-1), what will the 1st and last rows of the corresponding macroblock
look
like?
What I want to decribe to the decoder by sending a MV of (0,-1) is that
the
first 2 rows should be
2222...
3333...
the fifteenth should be
16 16 16...
and the last row could be anything.
if instead the first two rows are
2222...
2222...
and the last row
16 16 16...
then only the first row would be correct. My guess is that the last is the
behaviour that would occur.
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