NTSC 4x driver
ericball
Posts: 774
The NTSC4x TV driver displays a 1-20 longs x 1-484 image on an NTSC TV using standard 3pin TV DAC. Each bit is 1/4 colorburst cycle wide (fixed width). This is very similar to the Apple ][ low res & double hi-res graphics modes. The bitmap is padded horizontally and scaled vertically to 1-484 lines. Bits are displayed LSB first in display order (left to right, top to bottom).
Using 4 bits per pixel means each pixel is 1 colorburst cycle wide which will yeild 15 colors per pixel. (With some color artifacts between adjacent pixels.) Higher resolution (fewer bits per pixels) is possible, but color control is more difficult. There is also a tint parameter for adjusting the phase of the colorburst and therefore the colors displayed.
The current demo shows off the 15 color possibilities and the tint control.
(Sorry Baggers et. al., I can't see any realistic way of doing PAL with this scheme.)
Using 4 bits per pixel means each pixel is 1 colorburst cycle wide which will yeild 15 colors per pixel. (With some color artifacts between adjacent pixels.) Higher resolution (fewer bits per pixels) is possible, but color control is more difficult. There is also a tint parameter for adjusting the phase of the colorburst and therefore the colors displayed.
The current demo shows off the 15 color possibilities and the tint control.
(Sorry Baggers et. al., I can't see any realistic way of doing PAL with this scheme.)
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How many tint palettes are there before it starts going around the loop again?
here's a screen shot for those who don't have NTSC...
I did something similar awhile back.
Check out this thread http://forums.parallax.com/showthread.php?112910
Bean
Yep, same idea but different design decisions and implementation. I see your SX code was also inspired by the Apple ][. Great minds think alike.