D-MAC: Difference between revisions
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Among the family of '''MAC''' or '''M'''ultiplexed '''A'''nalog '''C'''omponents systems for [[television broadcasting]], '''D-MAC''' is a reduced bandwidth variant designed for transmission down cable. |
Among the family of '''MAC''' or '''M'''ultiplexed '''A'''nalog '''C'''omponents systems for [[television broadcasting]], '''D-MAC''' is a reduced bandwidth variant designed for transmission down cable. |
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* The data is [[ |
* The data is [[Bipolar encoding|duo-binary coded]] with a data burst rate of 20.25Mbit/s so that 0° as well as ±90° phasors are used. |
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* D-MAC has a bandwidth of 8.4 MHz versus 27 MHz for [[C-MAC]]. |
* D-MAC has a bandwidth of 8.4 MHz versus 27 MHz for [[C-MAC]]. |
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* Most cable systems work on [[EBU |
* Most cable systems work on [[EBU]] 7 MHz channel spacing, so this approach did not work universally. |
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* D-MAC's bandwidth problems were later fixed by D2-MAC. |
* D-MAC's bandwidth problems were later fixed by D2-MAC. |
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* [[DVB-S]], MAC technology was replaced by this standard |
* [[DVB-S]], MAC technology was replaced by this standard |
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* [[DVB-T]], MAC technology was replaced by this standard |
* [[DVB-T]], MAC technology was replaced by this standard |
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Revision as of 13:20, 2 May 2009
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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
- Multiplexed Analogue Components in "Analog TV Broadcast Systems" by Paul Schlyter
TV transmission systems
- Analog high-definition television systems
- PAL and SECAM, what MAC technology tried to replace
- A-MAC
- B-MAC
- C-MAC
- D-MAC
- E-MAC
- S-MAC
- D2-MAC
- HD-MAC, an early high-definition television standard allowing for 2048x1152 resolution.
- DVB-S, MAC technology was replaced by this standard
- DVB-T, MAC technology was replaced by this standard
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