C-MAC is the
television technology variant approved by the
European Broadcasting Union
The European Broadcasting Union (EBU; french: Union européenne de radio-télévision, links=no, UER) is an alliance of Public broadcasting, public service media organisations whose countries are within the European Broadcasting Area or who ar ...
(EBU) for satellite transmissions.
The digital information is modulated using 2-4PSK (
phase-shift keying
Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency reference signal (the carrier wave). The modulation is accomplished by varying the sine and cosine inputs at a ...
), a variation of quadrature PSK where only two of the phaser angles (±90°) are used.
* The
data capacity for C-MAC is 3Mbit/s.
* C-MAC data has to be sent to the transmitter separately from the vision.
* The transmitter switches between FM (vision) and PSK (sound/data) modulation during each television line period.
C-MAC variants : E-MAC
E-MAC (Extended MAC) is 16:9 version of C-MAC. Originally E-MAC was designed for 15:9 pictures, it later adopted the 16:9 aspect ratio.
* In E-MAC all the 4:3 information is transmitted exactly as in C-MAC so that C-MAC receivers are still compatible.
* E-MAC hides extra luminance and chrominance information in the field blanking interval and parts of the line blanking interval.
* E-MAC has a lower data capacity because luminance is hidden where data would usually be located.
* A 'steering' signal is transmitted to indicate to the 16:9 receiver whereabouts the 4:3 picture information.
* E-MAC receivers stitch the 4:3 and helper wide-screen data into a seamless 16:9 picture.
Technical details
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 sub-carrier.
* The MAC standard included a standard scrambling system, Euro-Crypt, a precursor to the standard DVB-CSA encryption system.
See also
TV transmission systems
*
Analog high-definition television systems
*
DVB-S
Digital Video Broadcasting – Satellite (DVB-S) is the original DVB standard for Satellite Television and dates from 1995, in its first release, while development lasted from 1993 to 1997. The first commercial applications was by Star TV in Asia ...
*
DVB-T
DVB-T, short for Digital Video Broadcasting – Terrestrial, is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in Singapore in Febr ...
*
Multiplexed Analogue Components
*
PAL
*
SECAM
References
{{reflist
Television technology
Video formats