My idea for a "green screen" edit: in theory vga.

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My idea for a "green screen" edit: in theory vga.

Postby Jeroen » Oct Mon 22, 2007 2:07 am

Living in "Pal land" as I call it. I've got scart. Wich means I also have rgb. My idea is to either:

1.) Use a sync-seperator to seperate the sync from composite, then blast sync into the sync pin and video into the green pin.

2.) Build a little device with a pic that looks at the outputs of the "terminal avr" and generates sync and video accordingly, the output is connected to the tv green and sync pin.

I hope this wil give me a nice green display.

edit: in theory this could also help for vga for those that want that. It could even stil be b/w for those that prefer. (instead of tying it to just green tie it to r,g,b.)
Jeroen
 
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Postby iam7805 » Oct Mon 22, 2007 6:43 pm

In theory your first idea should work and is probably easiest. Remember to put a resistor on the video line so not too much voltage is sent into the G pin (it expects the voltage to be 1/3 of what your sending into it I think...)

-iam
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Postby Jeroen » Oct Mon 22, 2007 8:32 pm

Mmmmmm seems your right. Black level is about the same i believe but the darn white level is 1v on composite and 700-750 on rgb. Thanks for noticing.
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Postby iam7805 » Oct Mon 22, 2007 9:02 pm

I found the voltages for PAL TV inputs and made a chart for you:

Code: Select all
RGB             - Highest Intensity:   0.7V
                - Lowest Intensity:    0V

Composite       - Highest Intensity:   1.0V
                - Lowest Intensity:    0.3V

Sync (for both) -                      0V


Enjoy! :)

-iam
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Postby Jeroen » Oct Tue 23, 2007 12:01 am

yay. Resistor to make voltage drop 0.3v! lol
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