C-MAC
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/88/PAL_and_D2-MAC_Transmission.png/300px-PAL_and_D2-MAC_Transmission.png)
The simultaneous PAL transmission of all TV-picture elements and the multiplexed transmission of the TV picture elements with D2-MAC.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/87/Multiplexed_Analogue_Components_transmission_%28simulation%29.jpg/300px-Multiplexed_Analogue_Components_transmission_%28simulation%29.jpg)
Simulated MAC signal. From left to right: digital data, chrominance and luminance
C-MAC is the television technology variant approved by the European Broadcasting Union (EBU) for satellite transmissions. The digital information is modulated using 2-4PSK (phase-shift keying), a variation of quadrature PSK where only two of the phaser angles (±90°) are used.[1]
- 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
- DVB-T
- Multiplexed Analogue Components
- PAL
- SECAM
References[]
Categories:
- Television technology
- Video formats