The data is duobinary coded with a data burst rate of 20.25 Mbit/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.
The simultaneous PAL transmission of all TV-picture elements and the multiplexed transmission of the TV picture elements with D2-MAC.A preview of actual D2-MAC signal. From left to right: digital data, chrominance and luminance with teletext packets between fields.
D-MAC consumed too much bandwidth for many applications, so D2-MAC was designed for European cable TV systems.
Luminance and chrominanceedit
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)edit
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.
By 1986, despite there being two standards, D-MAC and D2-MAC, favoured by different countries in Europe, an EU Directive imposed MAC on the national DBS broadcasters, to provide a stepping stone from analogue PAL and Secam formats to the eventual high definition and digital television of the future, with European TV manufacturers in a privileged position to provide the equipment required.
However, the Astra satellite system was also starting up at this time (the first satellite, Astra 1A was launched in 1989) and that operated outside of the EU's MAC requirements, due to being a non-DBS satellite. Despite further pressure from the EU (including a further Directive originally intended to make MAC provision compulsory in TV sets, and a subsidy to broadcasters to use the MAC format), most broadcasters outside Scandinavia preferred the lower cost of PAL transmission and receiving equipment.
In the 2000s, the use of D-MAC and D2-MAC ceased when the satellite broadcasts of the channels concern changed to DVB-S format.[2]
Multiplexed Analogue Components in "Analog TV Broadcast Systems" by Paul Schlyter
January 01, 1970
among, family, multiplexed, analogue, components, systems, television, broadcasting, reduced, bandwidth, variant, designed, transmission, down, cable, data, duobinary, coded, with, data, burst, rate, mbit, that, well, phasors, used, bandwidth, versus, most, ca. Among the family of MAC or Multiplexed Analogue Components systems for television broadcasting D MAC is a reduced bandwidth variant designed for transmission down cable 1 The data is duobinary coded with a data burst rate of 20 25 Mbit 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 The simultaneous PAL transmission of all TV picture elements and the multiplexed transmission of the TV picture elements with D2 MAC A preview of actual D2 MAC signal From left to right digital data chrominance and luminance with teletext packets between fields Contents 1 D2 MAC A fix for D MAC 2 Luminance and chrominance 3 Audio and scrambling selective access 4 History and politics 5 See also 6 References 7 External linksD2 MAC A fix for D MAC editMain article D2 MAC D MAC consumed too much bandwidth for many applications so D2 MAC was designed for European cable TV systems Luminance and chrominance editMAC 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 editAudio 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 History and politics editMAC was developed by the UK s Independent Broadcasting Authority IBA and in 1982 was adopted as the transmission format for the UK s forthcoming direct broadcast satellite DBS television services eventually provided by British Satellite Broadcasting The following year MAC was adopted by the European Broadcasting Union EBU as the standard for all DBS By 1986 despite there being two standards D MAC and D2 MAC favoured by different countries in Europe an EU Directive imposed MAC on the national DBS broadcasters to provide a stepping stone from analogue PAL and Secam formats to the eventual high definition and digital television of the future with European TV manufacturers in a privileged position to provide the equipment required However the Astra satellite system was also starting up at this time the first satellite Astra 1A was launched in 1989 and that operated outside of the EU s MAC requirements due to being a non DBS satellite Despite further pressure from the EU including a further Directive originally intended to make MAC provision compulsory in TV sets and a subsidy to broadcasters to use the MAC format most broadcasters outside Scandinavia preferred the lower cost of PAL transmission and receiving equipment In the 2000s the use of D MAC and D2 MAC ceased when the satellite broadcasts of the channels concern changed to DVB S format 2 See also editAnalog high definition television systems PAL and SECAM analogous technologies that MAC was designed to replace A MAC B MAC C 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 standardReferences edit https www etsi org deliver etsi i ets 300300 300399 300355 01 60 ets 300355e01p pdf bare URL PDF High Above Broadgate Publications April 2010 External links editMultiplexed Analogue Components in Analog TV Broadcast Systems by Paul Schlyter Retrieved from https en wikipedia org w index php title D MAC amp oldid 1189322855, wikipedia, wiki, book, books, library,
