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Many line doublers attempt to de-interlace the 480i NTSC signal, display-
ing both fields simultaneously in a 480-line "progressive" scan. Progres-
sive scanning combines the separate fields of odd-numbered lines and
even-numbered lines. Progressive scanning displays every line in a frame
in numeric sequence – line 1, 2, 3, 4 and so on up to line 480. Progres-
sive scan plays a central role in computer displays – where it helps to
make text more legible. Line doublers turn interlaced 480i signals into a
progressive 480P.
This concept works perfectly for still images, because the two fields match
up completely. But on moving images, the even field is captured 1/60
second later than the odd field. So a car traveling on the screen has
th
driven 1/60
second further down the street. And a baseball has slid 1/
60
th
second closer to home plate. For this reason, line-doublers require
elaborate motion-detection, motion-compensation and memory circuits.
This can get expensive, with the better line doublers costing $2,500 or
more.
A new solution: DRC
Sony's new Digital Reality Creation (DRC) circuitry is an all-new approach
to the problem of visible scanning lines. Not only does DRC create a
clearer picture by doubling the number of active scanning lines – it also
doubles the number of pixels on each scanning line. You get four times
the picture density of standard 480i, making this a significant step toward
the picture quality of true High Definition TV (HDTV).
th
How it works
The new DRC circuit is based upon a massive analysis of over tens of
thousands of High Definition TV picture patterns. Because there is a
fixed relationship between NTSC patterns and their HDTV equivalents,
Sony's exclusive microprocessor can simply replace the NTSC signal with
its correct DRC counterpart. In operation, the DRC circuit accepts a digi-
tally sampled 13.5 M H z input and generates a quadrupled 54.0 MHz
digital output.
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