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D-MAC

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The simultaneous PAL transmission of all TV-picture elements and the multiplexed transmission of the TV picture elements with D2-MAC.
Simulated MAC signal. From left to right: digital data, chrominance and luminance

Among the family of MAC or Multiplexed Analog Components systems for television broadcasting, D-MAC is a reduced bandwidth variant designed for transmission down cable.

  • The data is duo-binary coded with a data burst rate of 20.25Mbit/s so that 0° as well as ±90° phasors are used.
  • D-MAC has a bandwidth of 8.4 MHz versus 27 MHz for C-MAC.
  • Most cable systems work on EBU 7 MHz channel spacing, so this approach did not work universally.
  • D-MAC's bandwidth problems were later fixed by D2-MAC.

D2-MAC: A fix for D-MAC

D-MAC consumed too much bandwidth for many applications, so D2-MAC was devised for European cable TV systems.

Luminance and chrominance

MAC transmits luminance and chrominance data separately in time rather than separately in frequency (as other analog television formats do, such as composite video).

Audio and scrambling (selective access)

  • Audio, in a format similar to NICAM was transmitted digitally rather than as an FM subcarrier.
  • The MAC standard included a standard scrambling system, EuroCrypt, a precursor to the standard DVB-CSA encryption system.

See also

Weblinks

TV transmission systems


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