Forums > Jitter

Affecting a portion of a matrix

May 29, 2008 | 1:11 am

List,

I have a qt file that i’m playing normally, and I would like to use different audio filters to adjust different sections of the movie.

I have successfully completed the audio section, and now i’ve tackled the video section and i’ve run into a small problem.

I want to isolate a small section of the background movie, (say 1/12′th or so) and have that section’s luma respond to audio changes. I’ve done all this three different ways and have arrived at the same problem for all three approaches. I’ve tried probably more then three work-around’s to solve the problem as well.

I used the scissors object to cut apart the incoming movie file, adjust the hue/sat/luma, (Of each matrix) and then glued them all back together. Although, now there is a hard edge line between the separate ‘frames’. You would get something similar from crossing the inputs of a scissors/glue chain, to give you a visual clue of what I’m describing.

It is this hard edge that i wish to get rid of.

1st attempt: Post glue blur
After I glued the matrix back together, I tried to blur the resulting matrix slightly, to mask the lines. I’ve tried ave, fastblur, and probably a few more, none of which seemed to work well, and not degrade my FPS terribly.

2nd attempt: No Glue
For the second attempt, i removed the cut/paste objects and used the jitter matrix "look at" tools to separate the matrix, and to recombine them. Similar if not more noticeable lines were found.

3rd attempt: Alpha Channel wonders
for this third attempt, i tried to create an alpha channel to blend the edges away, and that was successfull, only now i see the places where i blended, which seem more noticeable to me then before, when they were lines.

So the general question i have for the list, is thus:
Is there a way that I have not found to adjust the values of a small section of a matrix? Is there a way to ease the lines that arrise from the cut/paste scissors/glue method that I’m currently using?

Any help would be appreciated, and if anyone knows a good way to grow/enlarge say a small white circle say, x pixels per bang… that would be great.

Thanks!

Michael Mathes
Moo TV
Nashville, TN


May 29, 2008 | 3:34 am

one solution might involve duplicating the section of the matrix you want to effect. one copy gets the effect and one copy remains unchanged. then composite the two sections together using an alpha map of your choice that satisfies your blending requirements.

then paste the section back to the original matrix (jit.scissors or whatever you use).

an easy way to get an alpha map is a 3×3 1 plane matrix. the center cell is white and the rest are black. send this into another matrix that is the size of your qt.movie, with interp on and adapt off. use this as the alpha channel of the effected matrix section.

-rob


May 29, 2008 | 10:31 pm

>
>
> an easy way to get an alpha map is a 3×3 1 plane matrix. the center cell is
> white and the rest are black. send this into another matrix that is the
> size of your qt.movie, with interp on and adapt off. use this as the alpha
> channel of the effected matrix section.

nice


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