[CinCV TNG] [impr] FindObj plugin part 2

Phyllis Smith phylsmith2017 at gmail.com
Sat Apr 14 23:56:32 CEST 2018


The latest GIT checkin has another whole column added for Replace Object.
I can't even begin to figure it out so am waiting to see Sam's tutorial!ed
However, GG says it should do just about everything.  About the
disappearing lines, GG says:

The draw border checkbox functions cause an enclosing rectangle to be drawn
around
the corresponding region of interest.  The lines drawn are 1 pixel wide,
and are drawn
into the media output. This makes them visible on the composer as image
data, BUT
the composer is usually drawn downscaled.  ie the media is 1920x1080, but
the composer
is drawn 800x500.  This causes about every other line to disappear, both
horizontally and
vertically.  This regular data interference pattern is commonly called
aliasing.  It creates a
regular beat frequency and creates a comb like pattern, or the "alias"
frequency on data.
To avoid aliasing, the data sample has to be bigger than the sample size,
in this case
ceiling(1920/800) or 3px wide, or the aliasing could delete the line
field.  Since the draw
border function is just one pixel wide, it is very susceptible to this
problem.  Since the
drag lines are drawn as composer objects, an extra step is used to beef up
the line
thickness.  If the draw border data is needed for media output (in the
rendering), then
1px is a good idea.  If the draw border data is needed for composer work,
then it
should also be beefed up.  So... how are you using these lines?


On Thu, Apr 12, 2018 at 2:04 PM, Sam <cinelerra at posteo.de> wrote:

>
> Here is a summary:
> 1. make size reduction of the replacement layer optional.
> 2. add replace object frame. (It already exists, but cannot be changed.)
> 3. keep the relative offset to the replacement frame to the object.
>
>
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