science

Multiplexed Analogue Components

Multiplexed Analogue Components is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Multiplexed Analogue Components rather than just read about it. In short: 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 interference between chrominance and luminance.

Key takeaways

Multiplexed Analogue Components belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Multiplexed Analogue Components to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Multiplexed Analogue Components from memory before moving on to harder problems.

Reference excerpt

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 interference between chrominance and luminance. MAC was originally proposed in the 1980s for use on a Europe-wide terrestrial HDTV system. Terrestrial transmission tests were conducted in France, although the system was never used for that purpose. Various variants were developed, collectively known as the "MAC/packet" family. In 1985 MAC was recommended for satellite and cable broadcasts by the European Broadcasting Union (EBU), with specific variants for each medium. C-MAC/packet was intended for Direct Broadcast Satellite (DBS), D-MAC/packet for wide-band cable, and D2-MAC/packet for both for DBS and narrow-band cable.

History MAC was originally developed by the Independent Broadcasting Authority in the early 1980, as a system for delivering high quality pictures via direct broadcast satellites, that would be independent of European countries' choice of terrestrial colour-coding standard. In 1982, MAC was adopted as the transmission format for the UK's forthcoming DBS television services, eventually provided by British Satellite Broadcasting. The following year, MAC was adopted by the EBU as the standard for all DBS broadcasts. By 1986, despite there being two variants (D-MAC and D2-MAC) favoured by different countries, an EU Directive imposed MAC on the national DBS broadcasters. The justification was to provide a stepping stone from analogue formats (PAL and SECAM) the future HD and digital television, placing European TV manufacturers in a privileged position to provide the equipment required. However, the Astra satellite system was also starting up at this time (the first satellite, Astra 1A, was launched in 1989), operating outside of the EU's MAC requirements, due to being a non-DBS satellite. Despite further pressure from the EU (including a Directive to make MAC compulsory in TV sets, and subsidies to broadcasters using MAC), most broadcasters outside of Scandinavia preferred the lower costs of PAL equipment, and the system had a limited adoption. In the 2000s, the use of D-MAC and D2-MAC ceased when satellite broadcasts changed to DVB-S format.

Broadcast Variants A number of broadcast variants exist, according to the way the digital signals are multiplexed with the MAC vision signal.

A-MAC was designed as a test-bed for the MAC concept. It was never used by any broadcaster, but eventually evolved into S-MAC. B-MAC was used in South Africa by Multichoice, Australia by Optus, the US by Primestar and American Forces Radio and Television Service. It was also used in parts of Asia until 2005, when it was replaced by digital compression. C-MAC required a bandwidth of about 22 MHz, making it problematic for broadcasting. It could carry eight high quality (15 kHz bandwidth) sound channels. It has a wide-screen backwardly compatible variant called E-MAC. D-MAC was a UK standard used by British Satellite Broadcasting for satellite broadcasts, needing a bandwidth of approximately 10.5 MHz. It could carry eight high quality (15 kHz bandwidth) sound channels It was used in Norway by NRK, transmitting 3 radio channels and 1 TV channel at one D-MAC channel. D2-MAC reduces the required bandwidth to 7.8 MHz, allowing the system to be used on cable and satellite broadcast. It could carry four high quality (15 kHz bandwidth) or eight lower quality audio channels. It was adopted by Scandinavian, German and French satellite broadcasts (CNBC Europe, TV3 (Sweden), TV3 (Denmark), EuroSport, NRK 1, TV-Sat 2, TDF 1, TDF 2, etc.). The system was used until July 2006 in Scandinavia and until the mid-1990s for German and French sound channels. HD-MAC was an early high-definition television standard, allowing for 2048x1152 resolution.

Studio (non-broadcast) MAC variants S-MAC or Studio MAC is a non-broadcast variant, used mostly in North America. The main advantages of this variant are:

Processing NTSC component signals yields better results (a higher quality image) than manipulating NTSC directly – thus the need to create S-MAC. It is not possible to mix standard MAC signals in the studio environment because the R-Y and B-Y components are carried on alternate lines. S-MAC's SECAM like approach to bandwidth reduction is technical annoyance, but most studio users are not affected by it. In S-MAC the luminance is compressed by 2:1 and the two chrominance signals by 4:1 so that all three may occupy the same line. S-MAC's vision bandwidth is 11 MHz, only ~2.8x that of NTSC's vision bandwidth of 4.2 MHz. S-MAC can be carried on a single circuit and converted losslessly to and from C-MAC at any stage. S-MAC is well suited for SNG applications (AKA: news gathering trucks).

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). This allows for full separation of the components. The signals are also time-compressed (with ratios of 3:2 for luminance and 3:1 for chrominance) and the two color difference signals are transmitted on alternate lines, further increasing compression. The color space was YPbPr, with a luminance component and red blue color difference chrominance components.

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, EuroCrypt, a precursor to the standard DVB-CSA encryption system

Technical details In MAC color is encoded using the YPbPr color space. Luma ( Y ′ {\displaystyle Y'} ) is derived from red, green, and blue ( R ′ , G ′ , B ′ {\displaystyle R',G',B'} ) after gamma-correction (formula similar to PAL): Y ′ = 0.2997 R ′ + 0.587 G ′ + 0.1145 B ′ {\displaystyle Y'=0.2997R'+0.587G'+0.1145B'}

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Multiplexed Analogue Components

Start with the simplest possible case. Write down what Multiplexed Analogue Components claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Multiplexed Analogue Components before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Multiplexed Analogue Components ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Multiplexed Analogue Components

In research: Multiplexed Analogue Components appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Multiplexed Analogue Components in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Multiplexed Analogue Components is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1982 introductions, Audiovisual introductions in 1982, British inventions, so understanding it makes those chapters shorter.
In everyday life: Look for Multiplexed Analogue Components outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Multiplexed Analogue Components in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Multiplexed Analogue Components means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Multiplexed Analogue Components out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Multiplexed Analogue Components in simple terms?

Why does Multiplexed Analogue Components matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Multiplexed Analogue Components?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Multiplexed Analogue Components.