From: awanderin@gmail.com   
      
   Exalted Being  writes:   
      
   I've played around with simulating the NTSC presentation of the input   
   signal, but rather than try to use a lookup table, I used signal   
   processing with digital filters for the luminance and chrominance   
   components of the signal.  It looked pretty realistic, and I could also   
   "turn" the hue, saturation, brightness, and contrast knobs, just like   
   you would have on an old-days television set.   
      
   From what I remember, in order to make a proper lookup table, I think I   
   would have needed about a 10 or 11 stage bit-string (pixel string?).   
   This was due to the low bandwidth of the chroma filter (something like   
   0.5 MHz), and so the effect of adjacent pixels is "felt" for quite a few   
   pixels.   
      
   I'm not sure how I would try to interpret the groups of six bits below.   
   I think you're going to have to do some calculations.   
      
   The book, Video Demystified, discusses the NTSC encoding and decoding   
   process fairly clearly.  Any edition of it will do.  I have the third   
   edition.  An old edition can probably be found for a low price.   
      
   The way I observed the "long"-lasting effect of one pixel on others, and   
   this might be wrong, but it seemed to me that both preceding and   
   following pixels had an effect on the color of the pixel.   
      
   I'm not sure of the state of my old code, otherwise I'd share it.   
      
   Probably the quickest thing for me to do would be to hook up a IIe to an   
   old NTSC color monitor I have and play around with bit patterns...   
      
      
      
      
   > The Apple II's video circuit outputs the picture signal to NTSC monitor. The   
   picture   
   > signal contains the binary data to be translated into 16 colors. NTSC's   
   chroma wheel has 8   
   > hues and 4 phases.   
   >   
   > How can degrees be determined from the group of 4 bits below?   
   >   
   > Low Brightness   
   > 1000 = 0 degrees   
   > 0100 = 90 degrees   
   > 0010 = 180 degrees   
   > 0001 = 270 degrees   
   >   
   > High Brightness   
   > 1101 = 0 degrees   
   > 1110 = 90 degrees   
   > 0111 = 180 degrees   
   > 1011 = 270 degrees   
   >   
   > Medium Brightness   
   > 1100 = 45 degrees   
   > 0110 = 135 degrees   
   > 0011 = 225 degrees   
   > 1001 = 315 degrees   
   >   
   > If I increase from group of 4 bits to group of 6 bits to support 64 colors   
   like Nintendo   
   > NES, the master OSC 21,477,270 MHz chip will be used for NTSC monitor.   
   >   
   > NTSC's chroma wheel has 12 hues and 6 phases.   
   >   
   > How can group of 6 bits be interpreted into degrees? Please fill the degrees   
   when "?   
   > degrees" are shown in the bottom of group of 6 bits.   
   >   
   > 100000 = 0 degrees   
   > 010000 = 60 degrees   
   > 001000 = 120 degrees   
   > 000100 = 180 degrees   
   > 000010 = 240 degrees   
   > 000001 = 300 degrees   
   >   
   > 110000 = 30 degrees   
   > 011000 = 90 degrees   
   > 001100 = 150 degrees   
   > 000110 = 210 degrees   
   > 000011 = 270 degrees   
   > 100001 = 330 degrees   
   >   
   > 110001 = 0 degrees   
   > 111000 = 60 degrees   
   > 011100 = 120 degrees   
   > 001110 = 180 degrees   
   > 000111 = 240 degrees   
   > 100011 = 300 degrees   
   >   
   > 010001 = ? degrees   
   > 101000 = ? degrees   
   > 010100 = ? degrees   
   > 001010 = ? degrees   
   > 000101 = ? degrees   
   > 100010 = ? degrees   
   >   
   > Thanks,   
   > EB   
      
   --   
   --   
   Jerry    awanderin at gmail dot com   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)