When scrambling takes place the incoming video is sampled at 4X the chroma
subcarrier rate of 3.58 MHz (14.3 MHz) and then processed by 384 Kilobytes
of high-speed memory. The video fields are then divided into seperate segments
and then are mixed with a time varying generator producing a random pattern
for each field segment, with additional intermixing, resulting in more than
10 X 10(to the power of 139) distinct fields.
Audio is sampled at a clock rate of 44 kHz and digitized by a 12-bit analog-
to-digital (A/D) converter, compressing the count down to 8-bits, and still
keeping the 12-bit dynamic range. Block coding aids in error concealment,
all the descrambling information (color bust, sync, and audio) is inserted
into the existing data by a digital controller. Composite information is now
digital-to-analog (D/A) converted which is followed by sync tip clamping,
noise is filtered, then the signal is amplified for the output stage.
The characteristics of the NTSC baseband are maintained, and lines 10-21 of
the vertical blanking interval are left 'in the clear' / unscrambled for
test signals such as (VITS) Vertical Interval Test Signals, (VIRS), Vertical
Interval Reference Signals, and for station identifications.
Go BACK To The Leitch Menu The Information Provided On This Page Is For Education Use Only & To Aid In The Understanding Of How Various Scrambling Systems Are Used & How They
Are Operated . . .
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