Multiplexed Analogue Components

The simultaneous PAL transmission of all TV-picture elements and the multiplexed transmission of the TV picture elements with D2-MAC.
Simulated MAC signal. From left to right: digital data, chrominance and luminance

Multiplexed analogue components (MAC) was a satellite television transmission standard, originally proposed for use on a Europe-wide terrestrial HDTV system, although it was never used terrestrially.

Technical overview

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)

History

MAC was originally developed by the Independent Broadcasting Authority (IBA) (dates unknown) in the UK for delivering high quality pictures via direct broadcast satellites that would be independent of European countries' choice of terrestrial colour-coding standard.[1]

Variants

A number of broadcasting variants of the MAC standard exist.

Studio (non-broadcast) MAC variants

S-MAC (Studio MAC): Used mostly in North America.

MAC system innovations

Mathematical

Broadcast engineering

Broadcast engineering

Technical challenges

Although the MAC technique is capable of superior video quality, (similar to the improvement of component video over composite in a DVD player), its major drawback was that this quality was only ever realized when the video signals being transmitted remained in component form from source to transmitter. If at any stage the video had to be handled in composite form, the necessary encoding/decoding processes would severely degrade the picture quality.

Technological obsolescence

Since the vast majority of TV stations and similar installations were only wired for composite video, the fitting of a MAC transmitter at the end of the chain had the effect of degrading the transmitted image quality, rather than improving it.

For this and other technical reasons, MAC systems never really caught on with broadcasters. MAC transmission technology was made obsolete by the radically new digital systems (like DVB-T and ATSC) in the late 1990s.

Although MAC transmission systems are still used, the technology is obsolete. It is expected that MAC will cease to be used for TV transmission by 2012.

See also

TV transmission systems:

References

  1. http://www.pembers.freeserve.co.uk/World-TV-Standards/Colour-Standards.html#MAC

External links

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