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66-537: BBC National DAB is a digital audio broadcasting multiplex in the UK , for a number of radio stations which have UK wide coverage. The multiplex is owned and operated by the BBC and is transmitted from a number of transmitter sites across the country; it only carries BBC radio stations. As of the end of 2017, more than 97% of the UK's population are within reach of the multiplex following

132-438: A .wav or .aiff file) has long been a standard across multiple platforms, but its transmission over networks is slow and expensive compared with more modern compressed formats, such as Opus and MP3. Many multimedia data streams contain both audio and video , and often some metadata that permits synchronization of audio and video. Each of these three streams may be handled by different programs, processes, or hardware; but for

198-533: A DAB ensemble can be increased by lowering average bit rates, but at the expense of the quality of streams. Error correction under the DAB standard makes the signal more robust but reduces the total bit rate available for streams. DAB broadcasts a single multiplex that is approximately 1.5 MHz wide (≈1,000 kilobits per second). That multiplex is then subdivided into multiple digital streams of between 9 and 12 programs. In contrast, FM HD Radio adds its digital carriers to

264-520: A DMB video subchannel can easily be added to any DAB transmission, as it was designed to be carried on a DAB subchannel. DMB broadcasts in South Korea carry conventional MPEG 1 Layer II DAB audio services alongside their DMB video services. As of 2017 , DMB is currently broadcast in Norway, South Korea, and Thailand. Fifty-five countries provide regular or trial DAB(+) broadcasts. In spectrum management ,

330-421: A combination of both higher audio quality and more stations. One of the most important decisions regarding the design of a digital radio broadcasting system is the choice of which audio codec to use because the efficiency of the audio codec determines how many radio stations can be carried on a fixed capacity multiplex at a given level of audio quality. Error-correction coding (ECC) is an important technology for

396-560: A consortium formed in 1986. The MPEG-1 Audio Layer II ("MP2") codec was created as part of the EU147 project. DAB was the first standard based on orthogonal frequency-division multiplexing (OFDM) modulation technique, which since then has become one of the most popular transmission schemes for modern wideband digital communication systems. A choice of audio codec , modulation and error-correction coding schemes and first trial broadcasts were made in 1990. Public demonstrations were made in 1993 in

462-468: A digital communication system because it determines how robust the reception will be for a given signal strength – stronger ECC will provide a more robust reception than a weaker form. The old version of DAB uses punctured convolutional coding for its ECC. The coding scheme uses unequal error protection (UEP), which means that parts of the audio bit-stream that are more susceptible to errors causing audible disturbances are provided with more protection (i.e.

528-465: A lower code rate ) and vice versa. However, the UEP scheme used on DAB results in a grey area in between the user experiencing good reception quality and no reception at all, as opposed to the situation with most other wireless digital communication systems that have a sharp "digital cliff", where the signal rapidly becomes unusable if the signal strength drops below a certain threshold. When DAB listeners receive

594-531: A lower bit rate. There are thousands of audio and video codecs, ranging in cost from free to hundreds of dollars or more. This variety of codecs can create compatibility and obsolescence issues. The impact is lessened for older formats, for which free or nearly-free codecs have existed for a long time. The older formats are often ill-suited to modern applications, however, such as playback on small portable devices. For example, raw uncompressed PCM audio (44.1 kHz, 16-bit stereo, as represented on an audio CD or in

660-504: A maximum bit rate that can be carried, but this depends on which error protection level is used. However, all DAB multiplexes can carry a total of 864 "capacity units". The number of capacity units, or CU, that a certain bit-rate level requires depends on the amount of error correction added to the transmission, as described above. In the UK, most services transmit using 'protection level three', which provides an average ECC code rate of approximately ⁠ 1 / 2 ⁠ , equating to

726-404: A maximum bit rate per multiplex of 1,184 kbit/s. Various different services are embedded into one ensemble (which is also typically called a multiplex ). These services can include: Traditionally, radio programmes were broadcast on different frequencies via AM and FM , and the radio had to be tuned into each frequency as needed. This used up a comparatively large amount of spectrum for

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792-544: A number of part-time services to broadcast. While these additional services are on air the bit rates of (one or more of) BBC Radio 3, BBC Radio 4, BBC Radio 5 Live, and data services are reduced. Two regularly-scheduled BBC Radio 4 long-wave programmes were, prior to April 2024, provided to DAB listeners by way of dynamic daily opt-outs which popped up on the national DAB multiplex. With the cessation of separate scheduling on long wave from 1 April 2024, these programmes were relocated to broadcast on Radio 4 Extra , ending use of

858-671: A pilot broadcast started in Bavaria in October 1995. In the UK, commercial stations started broadcasting in November 1999. For various reasons such as high receiver costs and limited reception, adoption of DAB had initially been slow, with the exception of the United Kingdom and Denmark. In the UK, DAB radio receivers were high selling and 10% of households owned a DAB radio as of 2005, helped by local manufacturers creating affordable receivers such as

924-640: A receiver receives a signal that has been transmitted from the different transmitters that are part of an SFN, the signals from the different transmitters will typically have different delays, but to OFDM they will appear to simply be different multipaths of the same signal. Reception difficulties can arise, however, when the relative delay of multipaths exceeds the OFDM guard interval duration, and there are frequent reports of reception difficulties due to this issue when propagation conditions change, such as when there's high pressure, as signals travel farther than usual, and thus

990-463: A rectangular byte interleaver rather than Forney interleaving in order to provide a greater interleaver depth, which increases the distance over which error bursts will be spread out in the bit-stream, which in turn will allow the Reed–Solomon error decoder to correct a higher proportion of errors. The ECC used on DAB+ is far stronger than is used on DAB, which, with all else being equal (i.e., if

1056-446: A relatively small number of stations, limiting listening choice. DAB is a digital radio broadcasting system that, through the application of multiplexing and compression, combines multiple audio streams onto a relatively narrow band centred on a single broadcast frequency called a DAB ensemble . Within an overall target bit rate for the DAB ensemble, individual stations can be allocated different bit rates. The number of channels within

1122-562: A requirement for all new cars sold in the EU since 2021. The original version of DAB used the MP2 audio codec ; an upgraded version of the system was later developed and released named DAB+ which uses the HE-AAC v2 (AAC+) audio codec and is more robust and efficient. DAB is not forward compatible with DAB+. Today the majority of DAB broadcasts around the world are using the upgraded DAB+ standard, with only

1188-712: A result most radio stations on DAB have a lower sound quality than FM, prompting complaints from listeners. As with DAB+ or T-DMB in Europe, FM HD Radio uses a codec based upon the MPEG-4 HE - AAC standard. HD Radio is a proprietary system from iBiquity Digital Corporation , a subsidiary of DTS, Inc. since 2015, which is itself owned by Xperi Corporation since 2016. DAB is an open standard deposited at ETSI. DAB can give substantially higher spectral efficiency , measured in programmes per MHz and per transmitter site, than analogue systems. In many places, this has led to an increase in

1254-452: A signal in this intermediate strength area they experience a "burbling" sound which interrupts the playback of the audio. The DAB+ standard incorporates Reed–Solomon ECC as an "inner layer" of coding that is placed around the byte interleaved audio frame but inside the "outer layer" of convolutional coding used by the original DAB system, although on DAB+ the convolutional coding uses equal error protection (EEP) rather than UEP since each bit

1320-447: Is a device that acts as both an encoder and a decoder on a signal or data stream, and hence is a type of codec. Endec is a portmanteau of encoder/decoder . A coder or encoder encodes a data stream or a signal for transmission or storage, possibly in encrypted form, and the decoder function reverses the encoding for playback or editing. Codecs are used in videoconferencing , streaming media , and video editing applications. In

1386-534: Is a nice step ahead in the digitisation of our radio landscape," commented Benjamin Dalle , the Flemish media minister. Norway was the first country to announce a complete switch-off of national FM radio stations. The switch-off started on 11 January 2017 and ended on 13 December 2017. The 2017 switch-off did not affect some local and regional radio stations. They can continue to transmit on FM until 2027. The timetable for

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1452-463: Is achieved without equalization by means of the OFDM and DQPSK modulation techniques. For details, see the OFDM system comparison table . Using values for Transmission Mode I (TM I), the OFDM modulation consists of 1,536 subcarriers that are transmitted in parallel. The useful part of the OFDM symbol period is 1.0 ms, which results in the OFDM subcarriers each having a bandwidth of 1 kHz due to

1518-409: Is being compressed and uses it as a disguise. This disguise appears as a codec download through a pop-up alert or ad. When a user goes to click or download that codec, the malware is then installed on the computer. Once a fake codec is installed it is often used to access private data, corrupt an entire computer system or to keep spreading the malware. One of the previous most used ways to spread malware

1584-457: Is equally important in DAB+. This combination of Reed–Solomon coding as the inner layer of coding, followed by an outer layer of convolutional coding – so-called "concatenated coding" – became a popular ECC scheme in the 1990s, and NASA adopted it for its deep-space missions. One slight difference between the concatenated coding used by the DAB+ system and that used on most other systems is that it uses

1650-401: Is no longer identifiable (visually, audibly, or both). Using more than one codec or encoding scheme successively can also degrade quality significantly. The decreasing cost of storage capacity and network bandwidth has a tendency to reduce the need for lossy codecs for some media. Many popular codecs are lossy. They reduce quality in order to maximize compression. Often, this type of compression

1716-612: Is normally a reduction in bit rate of their parent station. In 2010, the BBC published plans to close BBC Radio 6 Music and BBC Asian Network. These plans were later rejected, saving both stations from closure. Radio 6 Music was retained after listening figures increased and a campaign was set up on Facebook , which gained 180,000 supporters. In February 2024, the BBC proposed launching four services on DAB+ and BBC Sounds. The services will be sister stations to BBC Radio 1, BBC Radio 2 and BBC Radio 3, plus BBC Radio 1 Dance . The plans are subject to

1782-522: Is not forward compatible with DAB+, older DAB receivers cannot receive DAB+ broadcasts. However, DAB receivers that were capable of receiving the new DAB+ standard after a firmware upgrade were being sold as early as July 2007. Generally, if a receiver is DAB+ compatible, there will be a sign on the product packaging. DAB+ broadcasts have launched in several countries like Australia, Czech Republic, Denmark, Germany, Hong Kong (now terminated), Italy, Malta, Norway, Poland, Switzerland, Belgium (October 2017),

1848-441: Is not an ISO standard . There are also other well-known container formats, such as Ogg , ASF , QuickTime , RealMedia , Matroska , and DivX Media Format . MPEG transport stream , MPEG program stream , MP4 , and ISO base media file format are examples of container formats that are ISO standardized. Fake codecs are used when an online user takes a type of codec and installs viruses and other malware into whatever data

1914-489: Is the data link layer , in charge of statistical time-division multiplexing and frame synchronization . Finally, the physical layer contains the error-correction coding , OFDM modulation , and dealing with the over-the-air transmission and reception of data. Some aspects of these are described below. DAB initially only used the MPEG-1 Audio Layer II audio codec, which is often referred to as MP2 because of

1980-702: Is the codecs used in the sound cards of personal computers. A video codec accomplishes the same task for video signals. When implementing the Infrared Data Association (IrDA) protocol, an endec may be used between the UART and the optoelectronic systems. In addition to encoding a signal, a codec may also compress the data to reduce transmission bandwidth or storage space. Compression codecs are classified primarily into lossy codecs and lossless codecs. Lossless codecs are often used for archiving data in compressed form while retaining all information present in

2046-630: Is virtually indistinguishable from the original uncompressed sound or images, depending on the codec and the settings used. The most widely used lossy data compression technique in digital media is based on the discrete cosine transform (DCT), used in compression standards such as JPEG images, H.26x and MPEG video, and MP3 and AAC audio. Smaller data sets ease the strain on relatively expensive storage sub-systems such as non-volatile memory and hard disk , as well as write-once-read-many formats such as CD-ROM , DVD , and Blu-ray Disc . Lower data rates also reduce cost and improve performance when

BBC National DAB - Misplaced Pages Continue

2112-464: The HE-AAC v2 audio codec (also known as eAAC+ ) was adopted. AAC+ uses a modified discrete cosine transform (MDCT) algorithm. The new standard, which is called DAB+, has also adopted the MPEG Surround audio format and stronger error correction coding in the form of Reed–Solomon coding. DAB+ has been standardised as European Telecommunications Standards Institute (ETSI) TS 102 563. As DAB

2178-474: The Pure Evoke . In countries where DAB did not take off, efforts were made in later years to "re-launch" it using the newer DAB+ standard: it started gaining traction throughout the 2010s and finally took off in countries like France by 2019. DAB adoption in automobiles became increasingly common during this time, and by 2016 it was standard in most cars sold in the UK, Norway and Switzerland. In October 2005,

2244-786: The United Kingdom . The protocol specification was finalized in 1993 and adopted by the ITU-R standardization body in 1994, the European community in 1995 and by ETSI in 1997. Pilot broadcasts were launched in 1995: the Norwegian Broadcasting Corporation (NRK) launched the first DAB channel in the world on 1 June 1995 ( NRK Klassisk ), and the BBC and Swedish Radio (SR) launched their first broadcasts later in September while in Germany

2310-665: The World DMB Forum instructed its Technical Committee to carry out the work needed to adopt the AAC+ audio codec and stronger error correction coding . The AAC+ audio coding standard uses a modified discrete cosine transform (MDCT) audio data compression algorithm. This work led to the launch of the DAB+ system. Trials for DAB-IP were held in London in 2006, as " BT Movio". It competed with DVB-H and MediaFLO which were also under testing. By 2006, 500 million people worldwide were in

2376-584: The BBC started its first regular domestic broadcast of DAB+ in the Channel Islands and followed later with the start of local broadcasts in December 2021 in Cumbria and north Lancashire. Classic FM changed from DAB to DAB+ on 1 January 2024. Digital multimedia broadcasting (DMB) and DAB-IP are both suitable for mobile radio and TV because they support MPEG 4 AVC and WMV9 respectively as video codecs. However,

2442-457: The UK, Romania, Brunei, and the Philippines still using a significant number of legacy DAB broadcasts. DAB is generally more efficient in its use of spectrum than analogue FM radio, and thus can offer more radio services for the same given bandwidth. The broadcaster can select any desired sound quality, from high-fidelity signals for music to low-fidelity signals for talk radio, in which case

2508-541: The United Kingdom and the Netherlands. Malta was the first country to launch DAB+ in Europe in October 2008. South Africa began a DAB+ technical pilot in November 2014 on channel 13F in Band ;3. If DAB+ stations launch in established DAB countries, they can transmit alongside existing DAB stations that use the older MPEG-1 Audio Layer II audio format, and most existing DAB stations are expected to continue broadcasting until

2574-460: The United States has reached an agreement with Canada to restrict L-Band DAB to terrestrial broadcast to avoid interference. In January 2017, an updated DAB specification (2.1.1) removed Modes II, III and IV, leaving only Mode I. From an OSI model protocol stack viewpoint, the technologies used on DAB inhabit the following layers: the audio codec inhabits the presentation layer . Below that

2640-551: The bands that are allocated for public DAB services, are abbreviated with T-DAB . In the European Union , "the European Electronic Communications Code (EECC) entered into force on 20 December 2018, with transposition into national legislation by Member States required by 21 December 2020. The Directive applies to all EU member states regardless of the status of DAB+ in each country. This means that since

2706-459: The closure of FM signals in 2017 were as follows: SRG SSR , Switzerland's public-service broadcaster, will shut down its FM transmission infrastructure on 31 December 2024. The corporation concluded that maintaining FM broadcasts along with DAB+ and Internet streaming was no longer cost-effective, as due to widespread adoption of DAB+ the share of the public relying exclusively on FM was under ten percent and decreasing. All other FM broadcasters in

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2772-516: The completion of the switching on of a fourth set of new transmitters over the previous two years which had seen the reach increase from 93%. Any further expansion of DAB radio is awaiting a decision by government on any possible digital radio switchover. The following channels are receivable on any digital-equipped DAB radio in the BBC National DAB coverage area: The BBC National DAB multiplex makes use of dynamic ensemble reconfiguration to allow

2838-576: The country must shut down or convert to DAB+ by 31 December 2026. As of 2021 : DAB uses a wide-bandwidth broadcast technology and typically spectra have been allocated for it in Band III (174–240 MHz) and L band (1.452–1.492 GHz), although the scheme allows for operation between 30 and 300 MHz . The US military has reserved L-Band in the USA only, blocking its use for other purposes in America, and

2904-482: The coverage area of DAB broadcasts, although by this time sales of receivers had only taken off in the United Kingdom (UK) and Denmark . In 2006 there were approximately 1,000 DAB stations in operation worldwide. As of 2018, over 68 million devices have been sold worldwide, and over 2,270 DAB services are on air. In October 2018, the WorldDAB organisation introduced an all-new logo for DAB (specifically DAB+) to replace

2970-675: The data is transmitted, e.g., over the internet. Two principal techniques are used in codecs, pulse-code modulation and delta modulation . Codecs are often designed to emphasize certain aspects of the media to be encoded. For example, a digital video (using a DV codec) of a sports event needs to encode motion well but not necessarily exact colors, while a video of an art exhibit needs to encode color and surface texture well. Audio codecs for cell phones need to have very low latency between source encoding and playback. In contrast, audio codecs for recording or broadcasting can use high-latency audio compression techniques to achieve higher fidelity at

3036-402: The decreasing signal, providing more effective coverage over a larger area. DAB+ is a " green " platform and can bring up to 85 percent energy consumption savings compared to FM broadcasting (but analog tuners are more efficient than digital ones, and DRM+ has been recommended for small scale transmissions). Similar terrestrial digital radio standards are HD Radio , ISDB-Tb , DRM , and

3102-548: The dynamic pop-ups for these. The BBC has experimented with short-term "pop-up" digital radio stations, each broadcasting for approximately four days at a time, covering music festivals and other special events. The first to broadcast was BBC Radio 5 Live Olympics Extra in 2012, then BBC Radio 2 Eurovision launched for the first time in 2014, and was joined by BBC Radio 2 Country , BBC Music Jazz in 2015 and BBC Radio 2 50s in April 2016. When these temporary stations are on air, there

3168-529: The end of 2020, across all EU countries, all radios in new cars must be capable of receiving and reproducing digital terrestrial radio." Following the European Union's obligation in 2020 to include DAB+ receivers in new cars, Belgium has stopped all sales of analogue radio receivers from 1 January 2023. Thus, consumers are no longer able to purchase AM or FM receivers for domestic use. "The obligation to incorporate DAB+ for new cars and domestic radio receivers

3234-447: The inverse relationship between these two parameters, and the overall OFDM channel bandwidth is 1.537 MHz. The OFDM guard interval for TM I is 0.246 ms, which means that the overall OFDM symbol duration is 1.246 ms. The guard interval duration also determines the maximum separation between transmitters that are part of the same single-frequency network (SFN), which is approximately 74 km for TM I. OFDM allows

3300-490: The mid-20th century, a codec was a device that coded analog signals into digital form using pulse-code modulation (PCM). Later, the name was also applied to software for converting between digital signal formats, including companding functions. An audio codec converts analog audio signals into digital signals for transmission or encodes them for storage. A receiving device converts the digital signals back to analog form using an audio decoder for playback. An example of this

3366-408: The multimedia data streams to be useful in stored or transmitted form, they must be encapsulated together in a container format . Lower bitrate codecs allow more users, but they also have more distortion. Beyond the initial increase in distortion, lower bit rate codecs also achieve their lower bit rates by using more complex algorithms that make certain assumptions, such as those about the media and

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3432-428: The number of stations available to listeners, especially outside of the major urban areas. This can be further improved with DAB+ which uses a much more efficient codec, allowing a lower bitrate per channel with little to no loss in quality. If some stations transmit in mono, their bitrate can be reduced compared to stereo broadcasts, further improving the efficiency. Codec In electronic communications, an endec

3498-421: The original stream. If preserving the original quality of the stream is more important than eliminating the correspondingly larger data sizes, lossless codecs are preferred. This is especially true if the data is to undergo further processing (for example, editing ) in which case the repeated application of processing (encoding and decoding) on lossy codecs will degrade the quality of the resulting data such that it

3564-538: The packet loss rate. Other codecs may not make those same assumptions. When a user with a low bitrate codec talks to a user with another codec, additional distortion is introduced by each transcoding . Audio Video Interleave (AVI) is sometimes erroneously described as a codec, but AVI is actually a container format, while a codec is a software or hardware tool that encodes or decodes audio or video into or from some audio or video format. Audio and video encoded with many codecs might be put into an AVI container, although AVI

3630-453: The previous logo that had been in use since before DAB's initial launch in 1995. The term "DAB" most commonly refers both to a specific DAB standard using the MP2 audio codec, but can sometimes refer to a whole family of DAB-related standards, such as DAB+, DMB, and DAB-IP. WorldDAB , the organisation in charge of the DAB standards, announced DAB+, a major upgrade to the DAB standard in 2006, when

3696-620: The related DMB . The DAB standard was initiated as a European research project called Eureka-147 in the 1980s. DAB has been under development since 1981 at the Institut für Rundfunktechnik (IRT). The first DAB demonstrations were held in 1985 at the WARC-ORB in Geneva, and in 1988 the first DAB transmissions were made in Germany. Later, DAB was developed as a research project for the European Union ( EUREKA ), which started in 1987 on an initiative by

3762-401: The relevant regulatory approvals, including a Public Interest Test for the proposal to launch the stations via DAB+, a process which the BBC will start in the coming weeks and is expected to run until the end of 2024. Digital Audio Broadcasting Digital Audio Broadcasting ( DAB ) is a digital radio standard for broadcasting digital audio radio services in many countries around

3828-430: The signals are likely to arrive with a relative delay that is greater than the OFDM guard interval. Low power gap-filler transmitters can be added to an SFN as and when desired in order to improve reception quality, although the way SFNs have been implemented in the UK up to now they have tended to consist of higher power transmitters being installed at main transmitter sites in order to keep costs down. An ensemble has

3894-416: The sound quality can be noticeably inferior to analog FM. High-fidelity equates to a high bit rate and higher transmission cost. DAB is more robust with regard to noise and multipath fading for mobile listening, although DAB reception quality degrades rapidly when the signal strength falls below a critical threshold (as is normal for digital broadcasts ), whereas FM reception quality degrades slowly with

3960-406: The traditional 270 kilohertz-wide analog channels, with capability of up to 300 kbit/s per station (pure digital mode). The full bandwidth of the hybrid mode approaches 400 kHz. The first generation DAB uses the MPEG-1 Audio Layer II (MP2) audio codec, which has less efficient compression than newer codecs. The typical bitrate for DAB stereo programs is only 128 kbit/s or less and as

4026-451: The transmission powers remained the same), would translate into people who currently experience reception difficulties on DAB receiving a much more robust signal with DAB+ transmissions. It also has a far steeper "digital cliff", and listening tests have shown that people prefer this when the signal strength is low compared to the shallower digital cliff on DAB. Immunity to fading and inter-symbol interference (caused by multipath propagation)

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4092-505: The ubiquitous MP3 (MPEG-1 Audio Layer III). The newer DAB+ standard adopted the LC-AAC and HE-AAC , including its version 2 audio codecs, commonly known as AAC , AAC+ or aacPlus . AAC+ uses a modified discrete cosine transform (MDCT) algorithm, and is approximately three times more efficient than MP2, which means that broadcasters using DAB+ are able to provide far higher audio quality or far more stations than they could with DAB, or

4158-408: The use of single-frequency networks ( SFN ), which means that a network of transmitters can provide coverage to a large area – up to the size of a country – where all transmitters use the same transmission frequency block. Transmitters that are part of an SFN need to be very accurately synchronised with other transmitters in the network, which requires the transmitters to use very accurate clocks. When

4224-473: The vast majority of receivers support DAB+. In the UK, DAB+ launched in January 2016 following a trial period starting September 2014. Ofcom published a consultation for a new national multiplex containing a mix of DAB and DAB+ services, with the intention of moving all services to DAB+ in the long term. In February 2016, the new national network Sound Digital launched with three DAB+ stations. In August 2021

4290-589: The world, defined, supported, marketed and promoted by the WorldDAB organisation. The standard is dominant in Europe and is also used in Australia , and in parts of Africa and Asia ; as of 2022, 55 countries are actively running DAB broadcasts. DAB was the result of a European research project and first publicly rolled out in 1995, with consumer-grade DAB receivers appearing at the start of this millennium. Initially it

4356-422: Was expected in many countries that existing FM services would switch over to DAB, although the take up of DAB has been much slower than expected. As of 2023 , Norway is the first country to have implemented a national FM radio switch-off, with others to follow in the next years. In recent years, DAB has become the most popular radio listening platform in Norway, Switzerland and the UK , and has become

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