D-MAC
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D-MAC is a reduced bandwidth variant designed for transmission down cable.
- The data is duo-binary coded with a data burst rate of 20.25Mb/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.
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[edit] 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.
[edit] 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).
[edit] 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.
[edit] 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
