4 Jun
2008
4 Jun
'08
4:40 p.m.
How is the color video for display on a TV generated? I have a
reasonable understanding of how the composite video signal works,
although probably not all the details.
Each horizontal scan line consists of a lower frequency signal that
represents the brightness with higher voltage being darker. Added to
this is a higher frequency signal that represents color and the color is
determined not by amplitude, but by phase shift relative to a reference
generated during the horizontal retrace time.
So, if this is how the video signal works, then to generate 16 colors,
we could use one bit for a brightness level and 3 bits to select a
color. I can see a D F/F to hold the brightness level during a pixel
time.For color, I see an 8 bit shift register with the color signal
being shifted though and an 8 to 1 multiplexer to select the phase based
on the 3 color bits during each pixel time. Now add some resistors to
set the right levels and maybe some capacitors to take off the sharp
edges and you have a video signal.
I know this is ignoring the sync signals. I am really interested in how
you get color.
OK, so how close am I?
-chuck