NICAM

Key takeaways

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

Reference excerpt

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. In the 1980s, broadcasters began to use NICAM compression for transmissions of stereo TV sound to the public.

History

Near-instantaneous companding The idea was first described in 1964. In this, the 'ranging' was to be applied to the analogue signal before the analogue-to-digital converter (ADC) and after the digital-to-analogue converter (DAC). The application of this to broadcasting, in which the companding was to be done entirely digitally after the ADC and before the DAC, was described in a 1972 BBC Research Report.

Point-to-point links NICAM was originally intended to provide broadcasters with six high-quality audio channels within a total bandwidth of 2048 kbit/s. This figure was chosen to match the E1 primary multiplex rate, and systems using this rate could make use of the planned PDH national and international telecommunications networks. Several similar systems had been developed in various countries, and in about 1977/78 the BBC Research Department conducted listening tests to evaluate them. The candidates were:

A RAI system which used A-law companding to compress 14-bit linear PCM samples into 10 bits (14:10) A NICAM-type system proposed by Télédiffusion de France (14:9) NICAM-1 (13:10) NICAM-2 (14:11) NICAM-3 (14:10) It was found that NICAM-2 provided the best sound quality, but reduced programme-modulated noise to an unnecessarily low level at the expense of bit rate. NICAM-3, which had been proposed during the test to address this, was selected as the winner. Audio is encoded using 14 bit pulse-code modulation at a sampling rate of 32 kHz.

Broadcasts to the public NICAM's second role – transmission to the public – was developed in the 80s by the BBC. This variant was known as NICAM-728, after the 728 kbit/s bitstream it is sent over. It uses the same audio coding parameters as NICAM-3. The first NICAM digital stereo programme was the First Night of the 92nd edition of the Proms which was broadcast on BBC2 from the Crystal Palace transmitting station in London on 18 July 1986, though programmes were not advertised as being broadcast in stereo on the BBC until Saturday 31 August 1991, by which time the majority of the country's transmitters had been upgraded to broadcast NICAM, and a large number of BBC programmes were being made in stereo. ITV and Channel 4 only had begun advertising this capability 18 months later, coinciding with the Independent Broadcasting Authority rolling out NICAM on a transmitter-by-transmitter basis, which had begun in 1989 with the Crystal Palace and Emley Moor transmitters. It has been standardized as ETS EN 300 163.

Nations and regions using NICAM public broadcasts Several European countries had implemented NICAM with the PAL and SECAM TV systems

Belgium (analogue cable systems only; terrestrial switched to DVB-T) Denmark (historical, switched to DVB-T and DVB-C) Estonia (historical, switched to DVB-T and DVB-C) Finland (historical, switched to DVB-T and DVB-C) France (historical, switched to DVB-T) Greece (ANT1, New Hellenic Television, ET3 and ET1 - historical, switched to DVB-T) Hungary (historical, switched to DVB-T) Iceland (historical, switched to DVB-T) Ireland (historical, switched to DVB-T, DVB-C and IPTV) Latvia (historical, switched to DVB-T and DVB-C) Luxembourg (switched to DVB-T; cable?) Norway (historical, switched to DVB-T and DVB-C) Poland (Analogue cable systems only; terrestrial switched to DVB-T) Portugal (historical, switched to DVB-T) Romania (historical on terrestrial as switched to DVB-T2; on cable networks, still used by some operators providing analogue cable television) Russia Spain (historical, switched to DVB-T) South Africa (SABC 1, SABC 2, e.tv) Sweden (historical, switched to DVB-T and DVB-C) Ukraine United Kingdom (historical, switched to DVB-T) Some Asia-Pacific nations and regions have implemented NICAM

China Hong Kong (commonly used for dual language for programming containing both Cantonese and English/Mandarin/Japanese/Korean soundtracks; full switchover to DTMB with Dolby AC-3 audio encoding complete by 1 December 2020, NICAM became historical from that date) Macau (commonly used for dual language for programming containing both Cantonese and Portuguese/English/Mandarin/Japanese/Korean soundtracks; full switchover to DTMB with MPEG-1 Audio Layer II audio encoding complete by 30 June 2023, NICAM became historical from that date) Malaysia Formerly used by TV1, TV2, ntv7, 8TV, and TV9 around Klang Valley. TV3 also used NICAM on their VHF transmission frequency (Channel 12) in the Klang Valley, but used Zweikanalton on their UHF transmission frequency (Channel 29). Analog shutdown complete by 31 October 2019, thus NICAM and Zweikanalton broadcast became historical from that date. New Zealand (Full switchover to DVB-T complete by 1 December 2013. NICAM became historical from that date.) Indonesia Most national television networks in Indonesia used NICAM for analogue television. Analog shutdown complete by August 12, 2023, thus NICAM became historical from that date. Singapore (Used on Mediacorp Channel U. Full switchover to DVB-T2 complete by 1 January 2019. NICAM became historical from that date.) Sri Lanka Thailand Used on Channel 3, Channel 9 MCOT HD and Thai PBS, usually broadcast in dual-sound mode with sometimes in stereo mode. All analogue television service ceased since March 26, 2020. Switchover to terrestrial DVB-T2 with HE-AAC v2 codec, NICAM became historical from that date. Some other countries use Zweikanalton analogue stereo instead. Analogue stereo conversion thus begins.

Implementations No consumer grade equipment capable of NICAM modulation is presently known. Below is a non-exhaustive list of broadcast grade equipment capable of NICAM coding and or modulation:

Philips PM5685/PM5686/PM5686A Philips PM5687 Eiden 198A Pye/Varian/BBC Sound-in-Syncs solution IBA/RE Communications Sound-in-Syncs solution Tektronix 728E Rohde & Schwarz SBUF-E NICAM Module Barco NE-728 CableWorld CW-3830

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with NICAM

Start with the simplest possible case. Write down what NICAM claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, 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 NICAM 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 NICAM 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 NICAM

In research: NICAM appears in engineering 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 NICAM 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: NICAM is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1978 introductions, 1986 introductions, 1991 introductions, so understanding it makes those chapters shorter.
In everyday life: Look for NICAM 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.

How to study NICAM in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NICAM 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 NICAM out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NICAM in simple terms?

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.

Why does NICAM matter?

Because it connects several engineering 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 NICAM?

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 NICAM.