MAC procedure

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The simultaneous transmission of all television picture components with PAL and the successive transmission of the individual television picture components with D2-MAC
Simulated MAC signal. From left to right: digital data, chrominance and luminance
D2 MAC decoding in a Philips satellite receiver around 1990
TV-SAT-LNB for D2-MAC reception with HF filter

The MAC processes (English Multiplexed Analogue Components ) are television standards that were developed for satellite television in the early 1980s . The aim was to develop a standard that could be expanded in the future, which would offer better picture quality than PAL , SECAM or NTSC , and which could also be further developed into an HDTV standard ( HD-MAC ). Well that's scrambling (for pay TV ) possible.

Although the MAC processes implement multiplex processes , the abbreviation has nothing to do with the identical abbreviation MAC for Media Access Control , which is also associated with multiplexing .

functionality

The basis of the different MAC systems is the time- division multiplexed transmission of the individual signal components for brightness and color information. It avoids the effects that occur with PAL such as cross color and cross luminance . This means that, compared to PAL, each picture line is split, the left half containing the color information and the right half containing the pure brightness information.

The timing used - 50 fields and 15625 Hz line frequency - is otherwise the same as with PAL, so that a MAC signal can be converted into a PAL signal with simple means. However, the multi-channel sound is digitally transmitted uncompressed with the various MAC methods.

The MAC procedure could not prevail in Central Europe (especially France and Germany , which wanted to introduce it). As a result of several attempts by the EU Commission to compulsorily define D2-MAC as the only permissible standard for satellite television, the procedure fell into disrepute, particularly in Germany, as these regulations were viewed as an attempt to defeat the already overpowering position of the party that was significantly involved in the development French state company Thomson to expand in the European consumer electronics industry. By buying up a number of German consumer electronics manufacturers ( Nordmende , Telefunken , SABA , Dual etc.), most of which only the name remained, which was used for some time for its own goods and then sold to branded retailers, Thomson had during the 1980s and early 1990s in Germany a negative image. Since the analog SCART standard and a wide range of television programs in PAL via Astra already existed in the 1990s, there was little willingness to invest in a new digital system.

Only in Scandinavia and some pay TV channels was it often used with the EuroCrypt encryption system developed for the MAC process .

A-MAC

In the first version, the multiplexed image signal was frequency-modulated with a digital audio signal. It was practically not used.

B-MAC

With B-MAC, the digital audio signal is played in the blanking interval, i.e. 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 transfers between television stations and (encrypted) for the supply of satellite television to units of the US Army stationed abroad.

C-MAC

As a further development of B-MAC, the C-MAC phase modulates the audio signal by means of PSK , which offers space for several digital audio channels as well as additional digital data. The disadvantage of this method is the relatively high bandwidth of 27  MHz , which means that a C-MAC signal does not fit into the channel bandwidth available for terrestrial transmission or in the cable.

D-MAC

In order to be able to transmit the MAC signal in the bandwidth of 10.7 MHz available in the hyperband in the cable , D-MAC uses a duo-binary three-level coding for the digital (sound) data instead of binary coding (0 and 1) Logic (1, 0 and −1). The British Marcopolo satellites broadcast their television programs in D-MAC.

D2-MAC

By omitting some digital audio channels, it was possible to reduce the bandwidth of D2-MAC to 7 or 8 MHz, which made terrestrial and cable transmission possible.

The German TV-SAT 2 and the French TDF - television satellites beamed their television programs (eg one-Plus, 3Sat, RTL, Sat.1.) In D2-MAC and 4: 3 (16: 9 option) out in removed Cable television systems were fed in for this purpose, 12 MHz wide hyperband special channels.

The technical failure of TV-SAT 1 (due to a jammed solar cell sail), the switching of most of the French satellites to SECAM and the competition from the Copernicus and ASTRA satellites broadcasting in PAL quickly led to the failure of the standard. With cheaper, purely analog receivers, these satellites often offered more programs in the viewer's mother tongue. D2-MAC, on the other hand, was designed to transmit sound in several languages at the same time . Due to the RGB transmission and the uncompressed sound, the picture was almost studio quality. At least since the distribution of German programs via Astra, most of the satellite systems were converted from Kopernikus and TV-SAT 2 to Astra, which meant the de facto end for D2-MAC.

Only in Scandinavia could encrypted D2-MAC programs survive until the switch to encrypted DVB-S .

Loewe-TV Concept (1992) with 16: 9 picture tube and D2-MAC, internal satellite TV tuner and PiP

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