Multiplexed Analogue Components
In the MAC method (English Multiplexed Analogue Components) are television standards that were developed in the early 1980s for the satellite television. The aim was to develop an expandable in the future standard, which provides a better picture quality than PAL, SECAM or NTSC, and also to an HDTV standard (HD- MAC) could be further developed. Likewise, the scrambling is ( for pay TV) possible. While the MAC method put to multiplex method, the abbreviation has nothing to do with the same wording, also associated with multiplexing Abbreviation for Media Access Control MAC.
Operation
Basis of the different MAC systems is the multiplexed transmission of the individual signal components for brightness and color information. It avoids the occurring PAL effects such as cross color and cross luminance. This means that compared with PAL each image line is divided, with the left half of the color information and the right half contains the pure luminance information.
The timing used - 50 fields and 15625 Hz line frequency - is otherwise the same as PAL, so that a MAC signal by simple means can be converted into a PAL signal. The multi-channel sound will be transmitted uncompressed digital in the various MAC process.
The MAC method could in Central Europe ( particularly France and Germany, who wanted to introduce it) did not prevail. After several tests of the EU Commission, D2 - MAC forced to be defined as only permissible standard for satellite television, the process became particularly in Germany into disrepute, since these regulations were viewed as an attempt to the already -powerful position of the significantly concerned in the development French state-owned Thomson expand even further in the European consumer electronics industry. By buying up of several German consumer electronics manufacturer (North Mende, Telefunken, SABA, Dual, etc. ), of which usually each remained only the name that has been used for some time for their own goods and then sold to stamp dealers, Thomson has during the 1980s and early 1990s created a very negative image in Germany. Furthermore, since there was already a wide range of television programs in PAL via Astra in the 1990s, the willingness to invest was generally low in a new system.
Only in Scandinavia and some pay TV channels, it was often used with the developed method for the MAC Eurocrypt encryption system.
A- MAC
In the first version, the multiplexed image signal is frequency modulated with a digital audio signal. It has been practically used.
B-MAC
In B-MAC, the digital audio signal is recorded in the blanking interval, ie time-multiplexed with the image signals. Since it does not offer enough space for a suitably large number of audio channels, it was mainly used for satellite overdubs between TV stations and ( encrypted) for the care abroad stationed units of the U.S. Army with satellite TV.
C-MAC
As a further development of B-MAC, the sound signal is phase modulated by PSK in C-MAC, which can accommodate several digital audio channels as well as other additional digital data. The disadvantage of this method is the relatively large bandwidth of 27 MHz, thereby forming a C- MAC signal will not fit into the space available for the cable or terrestrial transmission channel bandwidth.
D-MAC
In order to transmit the MAC signal in the available in the Hyper band cable bandwidth of 10.7 MHz, used D-MAC in digital (audio ) data instead of binary coding ( 0 and 1), a duo- binary three-stage logic ( 1, 0 and -1). The British Marco Polo satellites beamed their television programs in D-MAC.
D2-MAC
By omitting some digital audio channels you managed to decrease in D2 - MAC the bandwidth to 7 or 8 MHz, creating a terrestrial and cable transmission was possible.
The German TV - SAT 2 and the French TDF television satellites beamed their television programs (eg One -Plus, 3sat, RTL, Sat1 ) in D2 - MAC and 4:3 (16:9 optional) from, were developed cable television systems for 12 MHz wide hyperband special channels fed.
The technical failure of the TV - SAT 1 (due to a jammed solar - sail ), switching of most French satellite to SECAM and the competition of sending in PAL Copernicus and ASTRA satellites quickly led to the failure of the standard. These satellites provided with cheaper purely analog receivers often more programs in the native language of the audience. D2 - MAC was, however, designed to transfer sound simultaneously in several languages . In the image it had nearly studio quality due to the RGB connection, and because of the uncompressed sound. Ever since the German distribution programs via Astra most satellite systems of Copernicus and TV - SAT 2 were converted to Astra what the actual end for D2 - MAC meant.
Only in Scandinavia encrypted D2-MAC programs were able to hold them to switch to encrypted DVB -S.