Registering frei0r plugin.

[Andre Caldas]

Dear Massimo,

First of all... by the way... if anyone wants to contribute, I would
be glad. I would probably publish it as GPL.


> can you explain in details what this mixer2 is supposed to do?

It compares track A and track B. Copies track B to output D and sets
D[alpha] to transparent whenever A and B are "equal".

I am a professor of mathematics. I have recorded some classes I edited
with Kdenlive. I know nothing about video editing. :-)
For example:
https://www.youtube.com/playlist?list=PLMG2ETzS-iy80kspoqaE2bgLWvZFf9i3u

I am recording a new set of lectures for a different subject. Now,
that I am a little savier, I want to be able to erase my background. I
have asked a question here
https://video.stackexchange.com/questions/34264/kind-of-chroma-key-using-a-key-frame
on how to do that, but I got like 7 views in a few days. So, I decided
to write a plugin. :-(

I realized it would be easy to implement a simple version of that but
that would not work very well due to already known issues with "chroma
keying". I got it working roughly some 8 hours ago. Shadows are the
biggest problem right now. But maybe I can fix it with better
illumination. It is not really usable, but much better than I
expected. I used "melt" to test it. I can share the resulting video if
you want.

Not a Kdenlive issue... but now I realize it would be better to write
an MLT plugin, so I could use a better color scheme, and also chain
some other processing. I can publish my code, if you want. The method
to determine if two pixels are the same needs to be improved. I have
thought of a dozen things that could be done, but I think it would
have to be an MLT plugin to do more advanced processing. I will also
need to "erase" the ink on the whiteboard.

Also, a different version of the plugin could be an "MLT filter"
instead of a "mixer2". It could compare to a specific keyframe,
instead of comparing to a track. But I would probably not be able to
do it with frei0r, and I am not really confident there is a GUI for
the "keyframe" value. So, by now, it is a "mixer2". I would be a nice
approach, and the image to be compared with could "evolve/adapt" for
the next keyframes.


> BTW: to add a frei0r plugin to Kdenlive, you have to add it to the
> frei0r plugin folder and create an xml ui file for it.

I have read a lot since I made this question. Following an advice I
got on MLT mailing list, I have added it to
~/.frei0r-1/lib/

I guess I need to provide an XML as described here:
https://invent.kde.org/multimedia/kdenlive/-/tree/master/data/effects

And I should probably put it in here:
~/.local/share/kdenlive/effects/


Cheers,
André Caldas.