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uyvy colormode: changing green to black?

January 11, 2013 | 5:54 am

is there a way to mask away the uyvy green (that is associated with neutral black tone in argb) so that it appears black? I attached a patch which demonstrates the problem.

I have discovered that affecting the contrast parameter of the cc.uyvy2rgba.jxs slab (boosting it to above 1.0) can yield the look I am after and eliminate the green, but then the original movie is too high-contrast, as a result.

I have trolled all the posts dealing with uyvy colormode, looked at all of the help patches like uyvy color-explorer, uyvy-composite patches, and can’t seem to find what I am after.

Has anyone else grappled with this?

Instructions for patch:
1) Main toggle on left to activate generic clip
2) Click red toggle switch to reveal the green behind the matrix, being rendered in open GL. (You will see green in the background, whereas in ARGB this would appear as black).

– Pasted Max Patch, click to expand. –

January 13, 2013 | 10:28 pm

What about trying to achieve the same effect using the scale & position attributes of the videoplane, and not erasing on every bang?

M


January 24, 2013 | 9:28 pm

Wouldn’t the background still be green? Altering the videoplane scale and position attr would reveal this same empty space?


January 25, 2013 | 10:45 am

Maybe I’m wrong but have you tried setting the color mode of jit.window to uyvy instead of argb ?


January 26, 2013 | 12:44 am

you can overcome this in a few different ways.
one way is to perform your matrix repositioning using the gpu, rather than the cpu (ie using slab/gl.pix rather than jit.matrix).

another, possible easier solution, is to mask out the green area.
below is a solution for this using jit.gl.pix.
notice that the dimensions of the matrix in colormode uyvy are 160 x 240, and the dimensions of the texture after the gl.slab conversion are 320×240. the gen code takes this into account.

– Pasted Max Patch, click to expand. –

January 31, 2013 | 10:07 pm

Rob,

Your solution is really impressive. I am exploring gen and was trying to make sense of what exactly you did.
Maybe if you find the time for further explanation I know I would really value it. Thanks for sharing this.

I came up with another solution (of sorts) in regards to this problem but dealing with a slightly different aspect of it.
I wanted to know if I could fade to black PRE slab conversion and was trying to figure out how to do this without invoking any GREEN.

What I came up with is probably a hack, as it’s not ‘broadcast black’ nor is it perhaps the most efficient in terms of processing.
But it works for me and I still seem to get 28-30 frames in my patch I’m using. (I would love to know if it’s even possible to do something like this in Gen but don’t even know where to begin, plus maybe it wouldn’t make sense to do it in Gen anyway[?]) ….

I used jit.traffic to make a certain colorspace alteration, and then tweaked the jit.scalebias and jit.brcosa to approximate black and get the fade-to-black PRE uyvy2rgba slab coversion effect I was after. There’s probably all kinds of room for improvement here, but just thought others may find this useful when dealing with uyvy and the differences in black + green, etc.

– Pasted Max Patch, click to expand. –

January 31, 2013 | 10:12 pm

just some further notes:

Turn on the main Start toggle to begin.
Enable the Red toggle to see the original src resized. (You should see green color in the empty space).
Use the Slider connected to xfade to fade to black. (You’ll notice that fading to black invokes purples and other colors here. You may alternately just bang a 1. to xfade to go to black immediately).


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