
Sampling NTSC at 4fs c gives 910 samples per total line
(STL). A count of 768 samples (3x28) encompasses the
active samples of a line, including the blanking transi-
tions. A count of 512 (29) lines is just slightly more than
the number of nonblanked lines in 480i scanning. The
numbers 768 and 512 were convenient for early
memory systems: 512 is the ninth power of 2, and 768
is 3 times the eighth power of 2. In the early days of
digital television, this combination - 768 and 512 -led
to very simple memory and addressing circuits for
framestores. The importance of this special combina- ...