B-MAC is a form of analog video encoding, specifically a type of

Multiplexed Analogue Components Multiplexed Analogue Components (MAC) was an analog television standard where luminance and chrominance components were transmitted separately. This was an evolution from older color TV systems (such as PAL or SECAM) where there was interferen ...

(MAC) encoding. MAC encoding was designed in the mid 80s for use with

Direct Broadcast Satellite Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems ...

systems. Other analog video encoding systems include

NTSC NTSC (from National Television System Committee) is the first American standard for analog television, published and adopted in 1941. In 1961, it was assigned the designation System M. It is also known as EIA standard 170. In 1953, a second ...

PAL Phase Alternating Line (PAL) is a color encoding system for analog television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

and

SECAM SECAM, also written SÉCAM (, ''Séquentiel de couleur à mémoire'', French for ''sequential colour memory''), is an analog color television system that was used in France, Russia and some other countries or territories of Europe and Africa. ...

. Unlike the Frequency-Division Multiplexing (FDM) method used in those, MAC encoding uses a Time-Division Multiplexing (TDM) method. B-MAC was a proprietary MAC encoding used by

Scientific-Atlanta Scientific Atlanta, Inc. was a Georgia, United States–based manufacturer of cable television, telecommunications, and broadband equipment. Scientific Atlanta was founded in 1951 by a group of engineers from the Georgia Institute of Technology, ...

for encrypting broadcast video services; the full name was "Multiple Analogue Component, Type B".

Usage

Both

625 __NOTOC__ Year 625 ( DCXXV) was a common year starting on Tuesday of the Julian calendar. The denomination 625 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe ...

and 525 line versions of B-MAC were developed and used. This system was used in South Africa by

Multichoice MultiChoice is a South Africa, South African company that operates DStv, a major satellite television service in Sub-Saharan Africa. The company also operates GOtv Africa, GOtv, a minor satellite TV service operating in 9 countries, and Showmax, ...

, and Australia by

Optus Singtel Optus Pty Limited is an Australian Telecommunications in Australia, telecommunications company headquartered in Macquarie Park, a suburb in the Northern Sydney region of Sydney, New South Wales, Australia. It is a wholly owned subsidiar ...

(for

TVRO Television receive-only (TVRO) is a term used chiefly in North America, South America to refer to the reception of satellite television from FSS-type satellites, generally on C-band analog; free-to-air and unconnected to a commercial DBS provi ...

until 2000). B-MAC was used for satellite broadcasts of the

American Forces Radio and Television Service The American Forces Network (AFN) is a government television and radio broadcast service the United States Armed Forces provides to soldiers stationed or assigned overseas, and is headquartered at Fort Meade in Maryland. AFN comprises two sub ...

from the early 1980s until 1996-1997 when the analogue standard was replaced by the digital

PowerVu PowerVu is a conditional access system for digital television developed by Scientific Atlanta. It is used for professional broadcasting, notably by Retevision, Bloomberg Television, Discovery Channel, AFRTS, ABS-CBN, GMA Network, and American ...

system. B-MAC was used for

direct to home Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems ...

satellite applications up to the mid-1990s when

Primestar PrimeStar was an American direct broadcast satellite broadcasting company formed in November 1990 by seven cable television companies including Comcast Corp. and TCI Communications Corp. PrimeStar was the first medium-powered DBS system in the U ...

switched to an all-digital delivery system.

Technical details

MAC transmits

luminance Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls wit ...

and

chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying Luma (video), luma signal (or Y' for short). Chrominance is usu ...

data separately in time rather than separately in frequency (as other analog television formats do, such as

composite video Composite video, also known as CVBS (composite video baseband signal or color, video, blanking and sync), is an analog video format that combines image information—such as brightness (luminance), color (chrominance), and synchronization, int ...

). B-MAC uses

teletext Teletext, or broadcast teletext, is a standard for displaying text and rudimentary graphics on suitably equipped television sets. Teletext sends data in the broadcast signal, hidden in the invisible vertical blanking interval area at the to ...

-style non-return-to-zero (NRZ) signaling with a capacity of 1.625 Mbit/s. The video and audio/data signals are therefore combined at baseband. For audio, a format similar to

NICAM Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Spi ...

was transmitted digitally rather than as an FM subcarrier. The MAC standard included a standard scrambling system,

EuroCrypt EuroCrypt is a conditional access system for Multiplexed Analogue Components-encoded analogue satellite television Satellite television is a service that delivers television programming to viewers by relaying it from a communications satell ...

, a precursor to the standard

DVB-CSA The Common Scrambling Algorithm (CSA) is the encryption algorithm used in the Digital Video Broadcasting, DVB digital television broadcasting for encrypting video coding, video streams. CSA was specified by ETSI and adopted by the DVB consortium i ...

encryption system. In MAC color is encoded using the

YPbPr YPbPr or Y'P'bP'r, also written as , is a color space used in video electronics, in particular in reference to component video cables. Like YCBCR, it is based on gamma corrected RGB primaries; the two are numerically equivalent but YPBPR is de ...

color space.

Luma Luma or LUMA may refer to: Arts and entertainment * LUMA Projection Arts Festival, an annual event in Binghamton, NY, US * Unified Theory (band), formerly called Luma * Luma (Mario), a fictional species from the video game ''Super Mario Galaxy'' ...

(

Y'

) is derived from red, green, and blue (

R', G', B'

) after gamma-correction (formula similar to

Y'= 0.2997R' + 0.587G' + 0.1145B'

Chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying Luma (video), luma signal (or Y' for short). Chrominance is usu ...

is computed based on

B-Y

and

R-Y

differences, generating two compressed and weighted color-difference signals,

P

and

P

. The

Y'

signal range is between -0.5 and 0.5 volts while

P

and

P

signals vary between -0.65 to 0.65 volts. The following table lists the main technical parameters of B-MAC variants:

References

External links

Multiplexed Analogue Components
in "Analog TV Broadcast Systems" by Paul Schlyter {{Analogue TV transmitter topics Video formats Television technology

Usage

Technical details

See also

References

External links