Proposed as a national standard in 2004 , Audio Video Standard is a compression audio and video system developed by the Audio Video Coding Standard Workgroup of China. Designed to replace AAC audio and H.264/MPEG-4 AVC at a lower price than commonly used systems in the rest of the world. It is not much used outside China. AVS+ was designed to provide performance with reduced complexity.
In 2013 work started on AVS2: designed to compete with HEVC(H.265).
Informal word used to describe when streaming media suddenly ‘hits the buffers’ – stops. This is usually due to a lack of bandwidth when viewing video over the internet. In recent years the implementation of adaptive streaming schemes, as well as faster internet, have together greatly reduced the occurrence of buffering, making the viewing of video delivered via the internet a non-buffered experience.
Broadcast eXchange Format standardizes interfaces among systems that deal with content metadata, content movement, schedules and as-run information. This is standardized in SMPTE RP 2021 and simplifies interoperability between applications. BXF provides a standard where there were a large number of diverse ‘pet’ or old file and data formats used in areas including schedules, playlists, record lists, as-run lists, content metadata, content movement instructions.
BXF makes it possible for all its users to have a common standard for the efficient exchange of data between all components of broadcast automation and business systems.
Cable Modem Termination System is located at a cable headend / hub and connects to the customers’ lines and can provide fast data services, including Internet, to its customers.
Coded Orthogonal Frequency Division Multiplexing – a modulation scheme which is used by the DVB digital television system. It allows for the use of either 1705 carriers (usually known as ‘2K’), or 6817 carriers (‘8K’). Concatenated error correction is used. The ‘2K’ mode is suitable for single transmitter operation and for relatively small single-frequency networks with limited transmitter power. The ‘8K’ mode can be used both for single transmitter operation and for large area single-frequency networks (SFN). The guard interval is selectable. The ‘8K’ system is compatible with the ‘2K’ system. At the start of DVB transmissions in the United Kingdom in November 1998, only 2K was possible, but soon after 8K was also possible.
There has been much discussion about the relative merits of COFDM vs the 8-VSB scheme used in the ATSC standard (OFDM may be considered for upcoming ATSC 3). The Japanese ISDB system uses a similar scheme, OFDM, and the Chinese have developed their own transmission scheme the DMB-T/H standard – not to be confused with the T-DMB Korean standard modulation – both significantly different COFDM implementations.
This is a file system that rotates and delivers its content into a network at a defined point in a cycle, for example, teletext pages. It is a method to make a large amount of information or data files available within a reasonably short time following a request. The data is inserted into the digital broadcast transport stream.
See also: IP over DVB
See: IP over DVB
Digital Multimedia Broadcasting. Developed and first adopted in South Korea (2005), DMB is a digital transmission system for television, radio and datacasting to mobile devices/phones and can operate over satellite (S-DMB) or terrestrially (T-DMB). DMB is based on the Eureka 147 Digital Audio Broadcasting (DAB) standard, and has similarities with DVB-H, a competing mobile TV standard.
T-DMB (ETSI standard TS 102 427 and TS 102 428) uses MPEG-4 H.264 for video and HE-AAC V2 for the audio, together encapsulated in an MPEG-2 transport stream (TS). The encoded TS is broadcast on DAB in data stream mode. Application devices include mobile phones, portable TV, and PDAs as well as data/radio for cars.
Digital Satellite Service. One of the terms used to describe DTV services distributed via satellite.
Digital Video Broadcasting, the group, with over 200 members in 25 countries, which developed the preferred scheme for digital broadcasting in Europe. Initially the DVB Group put together a portfolio of broadcast standards; the major ones including a satellite system, DVB-S, and now the more efficient DVB-S2, a matching cable system, DVB-C (and now DVB-C2), and a digital terrestrial system, DVB-T (and now DVB-T2). DVB-H is a newer broadcast standard designed for terrestrial operation with hand-held devices, typically mobile TVs, phones and tablets where power must be conserved.
DVB-S (1995) is the original DVB forward error coding and modulation standard for satellite television. DVB-S is used for both broadcast network feeds and for direct broadcast satellite services.
DVB-S2 (2003) is used for all new European digital satellite multiplexes, and satellite receivers will be equipped to decode both DVB-S and DVB-S2. Currently its main use is to distribute HDTV. DVB-S2 is based on DVB-S adding two key features: allowing changing encoding parameters in realtime (VCM, Variable Coding and Modulation) and ACM (Adaptive Coding and Modulation) to optimize the transmission parameters for various users for a claimed net performance gain of 30 percent (ie, more data transmitted for more channels).
DVB-T is a transmission scheme for digital terrestrial television (DTT). Its specification was approved by ETSI in February 1997 and DVB-T services started in the UK in autumn 1998.
As with the other DVB standards, MPEG-2 sound and vision coding are used. It uses Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation. It enables effective operation in very strong multipath environments (that cause picture ‘ghosting’ in analog TV reception), meaning in can operate an overlapping network of transmitting stations using the same frequency. In the areas of overlap, the weaker received signals are rejected. Where transmitters carry the same programming the overlapping signals provide more reliable reception, known as a single-frequency network (SFN).
DVB-T2 (2009). The DVB TM-T2 technical group worked on a more advanced DTT standard focusing on modulation, channel encryption and signal layout. The resulting DVB-T2 offers a 50 percent increase in payload capacity under similar reception circumstances. Its error correction coding, shared with DVB-S2 and DVB-C2, involves LDPC (Low Density Parity Check) coding combined with BCH (Bose-Chaudhuri-Hocquengham) coding, offering a very robust signal. Along with other changes it is more flexible, supporting SD, HD, UHD, mobile TV, radio, or any combination thereof.
DVB-C (1994) for digital transmission via cable transmits an MPEG-2 or MPEG-4 family digital audio/digital video stream, using a QAM modulation with channel coding.
DVB-C2 (2010) almost doubles the payload so relieving the many cable networks that were running at near capacity.
The DVB digital TV standards are used around the world with notable exceptions being ATSC in the USA and Canada, ISDB in Japan, DMB-T/H (Digital Multimedia Broadcast-Terrestrial/ Handheld) in China, and T-DMB in South Korea.
There are several additional DVB transmission standards that can be found on the website. These include DVB-RCS2 that provides an air interface specification for low-cost two-way satellite broadband VSAT (very small aperture terminal) systems to provide dynamic, demand-assigned transmission capacity for a wide range of users. It provides a broadband Internet connection with no need of local terrestrial infrastructure. Data speeds of several tens of Mb/s down to terminals, and up to 10 Mb/s or more can be achieved.
DVB-CPCM DVB Content Protection and Copy Management is a digital rights management standard which is under development. This is intended as a practical rights management system primarily for European digital television; but other countries may adopt it.
CPCM allows adding information to digital content, such as TV programs, that shows how content may be used by other CPCM-enabled devices. Content providers can store flags with the content to indicate how it may be used. All CPCM-enabled devices should obey these flags, allowing or denying its movement, copying to other CPCM devices, controlling use on other equipment, and observing time limits.
The full technical specification of DVB-CPCM is available for free downloading at the DVB website.
DTV allows broadcasters to transmit electronic program guides. For many, this service is considered essential to keep viewers up to date with, and enable them to navigate between, the large number of channels that DTV services can deliver. The program guide database allows a receiver to build an on-screen grid of program information and contains controls to ease navigation.
Full HD is a term describing video at 1920 x 1080 resolution. Generally this appears as one of the many logos stuck on a new flat panel TV set or screen that can display all the pixels of 1920 x 1080 images supplied from HD sources such as broadcast transmissions and HD DVD and Blu-ray Discs.
The panels only use progressive scans so they are showing 50P and 59.94P frame rates. The logo can also appear on other consumer products such as camcorders using the 1920 x 1080 image size.
Hybrid Broadband Broadcast TV (HbbTV) is a European initiative to provide both broadcast and broadband/web content on viewers’ screens. It combines linear (normal) channels with internet content, providing interactivity and the ability to deliver service packages to all relevant devices.
Differences in viewing between computer and TV do not help, such as viewing distance: lean forward (PC) and lean back (TV), lack of mouse and keyboard on TVs, different colors: PC black text on white – the reverse on TV, and lack of computing power in TVs.
See also: Second screen
Integrated Digital TV receiver. For viewers to receive DTV services they require a receiver either in the form of a new television set with the tuner and digital decoder built in (IDTV) or a set-top box. IDTVs typically include provision for all widely available terrestrial DTV services, so cable and satellite still require a set-top box. Note that although the set may be able to receive HD the screen may not be able to display the full sized 1920 x 1080 HD picture. In this case processing is included to re-size the pictures to fit the screen.
A service that may be enabled with DTV which allows viewers to participate or access more information about the program. The interactivity may be implemented by selecting different TV channels (unknown to the viewer) or by a return control path to the service provider. Besides using a phone line, DVB has devised return control paths for satellite (DVB-RCS), cable (DVB-RCC) and terrestrial (DVB-RCT). Some consider interactivity is the future of television – the ‘killer app(lication)’ that will make DTV a commercial success. Others talk of lean back (viewing) and lean forward (interaction) being very different attitudes of both body and mind and question whether the two belong in the same place.
See also: Return control
The delivery of IP data and services over DVB broadcast networks. Also referred to as datacasting, this takes advantage of the very wideband data delivery systems designed for the broadcast of digital television, to deliver IP-based data services – such as file transfers, multimedia, Internet and carousels, which may complement, or be instead of, TV.
Due to DVB-T’s ability to provide reliable reception to mobile as well as fixed receivers, a new standard DVB-H has been added to send IP-style service to people on the move – typically to phones. For interactivity, a return path can be established by the phone.
Internet Protocol Television refers to the use of the IP packetized data transport mechanism for the delivery of streamed realtime (live streaming) and downloaded television signals across a network. This is a huge subject as video accounts for an increasingly large part of internet traffic. Cisco predicts that, excluding video peer-to-peer file sharing, 79 percent of domestic internet traffic will be video by 2018, up from 66 percent in 2013. And that including file sharing, it will take between 80-90 percent of global consumer traffic in 2018.
A method used to show higher aspect ratio (e.g. 16:9) images on a low aspect ratio (e.g. 4:3) display. While all the contents of the pictures can be seen there are strips of (usually) black above and below the picture which some people do not like. Now that nearly all viewers have 16:9 screens, the use of letterbox is passing into history.
Newsroom Computer System. The name sprang up when the only computer in a TV news area was used for storing and editing the text available from news services. It also created the running order for the bulletin and was interfaced to many other devices around the production studio. Today the NRCS lives on… but it is no longer the only computer around the newsroom! All journalists can access the the NRCS which stores all the video, audio, text needed for them to edit their story at their workstation, which could be anywhere. Also rundowns, prompter scripts and more tasks are undertaken by modern NRCS that may link more systems, such as video editing.
See also: MOS
Near Video On Demand. A service that offers quick access to on-demand program material, sometimes achieved by providing the same program on a number of channels with staggered start times, and so there is not too long to wait for your chosen movie to start. NVOD made sense when programs were only recorded on tape. Now the technology has moved on to computer disk storage, access to programs has hugely improved, so NVOD is no longer needed.
Orthogonal Frequency Division Multiple Access is a technology used for terrestrial radio return channels. Generally it provides several users with simultaneous low data rate transmission for fixed and mobile applications. Power can be less than a Watt and will communicate over considerable distances. OFDMA is used in the IEEE 802.16-2005 Mobile WiMAX broadband wireless access standard, enabling mobile DSL services and mobile telephony to provide customers with enhanced voice and data services.
Return control is needed for interactive television. Typically it needs only to offer quite a low data rate but have little latency, as action should be followed as soon as possible by reaction. DVB includes methods for return paths for cable, DVB-RCC; satellite-RCS; and terrestrial–RCT, services. While cable and terrestrial are devised to operate economically for individual viewers, the satellite solution is more appropriate for head-ends or groups – due to cost. Interestingly DVB-RCS has been adopted by many companies operating in the general telecoms world.
See also: WiMax
The area of picture into which it is considered safe to place material, graphics, text or action, so that it will be viewable when received at home. Initially this was necessary with 4:3 aspect ratio CRT screens as they were always overscanned to avoid showing the ‘black’ that surrounded the active picture. Typically 5% in from the edges was considered safe. Today most TV screens are flat panels, and the pictures are 16:9. There are controls for zooming or changing the aspect ratio, but usually all the active picture is displayed on the screen.
See also: Aspect ratio (of pictures)
Standard Definition Television. Digital television systems that operate using standard definition video formats, i.e. 720 x 480/59.94I or 720 x 576/50I. Both these may carry 4:3 or 16:9 images, and in all cases, the pixels are not square. All HDTV and UHDTV digital standards describe square pixels.
The term used to describe the simultaneous transmission of a program over more than one channel: for example one SD, one HD, a third on the Internet as well as services to mobile devices. All versions are transmitted at the same time but due to coding times and system latency they are unlikely to be synchronous.
A group of transmitters all working on the same frequency within range of each other. Usually these will interfere causing serious problems with reception. However with DVB-T2 transmission, and the TV channels all running on the same locked frequencies over all transmitters, any interference is constructive, adding to the quality of the received signal. SFN’s are very efficient with radio frequency spectrum use as, for example, all transmissions of a group of TV channels around a country can use the same channel frequency throughout a network. Also the constructive interference makes it easier to get good reception, sometimes even with a modest antenna.
This increases the overall efficiency of a multi-channel digital television transmission multiplex by varying the bit-rate of each of its channels to take only that share of the total multiplex bit-rate it needs at any one time. The share apportioned to each channel is predicted statistically with reference to its current and recent-past demands. For example, football, generally with much action and detail (grass and crowds), would use a higher data rate than a chat show with close-ups and far less movement. The data streams for each program are monitored and their bit rates varied accordingly to fit the bit rate of the whole multiplex.
See also: Variable bit rate
Also known as 8K UHD, pioneered by the Japanese broadcaster NHK this is a very large format television system with a pictures size of 7680 x 4320 pixels. It is proposed to run at frame rates from 23.98 to 120 Hz and start broadcasting by 2020. SHV can also support a 22.2 sound system with 22 speakers and two woofers.
A timing reference signal developed for HD. Typically this is originated by an sync-pulse generator and is distributed to most of the technical equipment, including cameras, mixer/switcher, and video processing equipment in a studio or truck so they all operate in sync.
With the opportunity to devise a new timing signal, the TLS signal combines a negative and positive pulse that is symmetrically above and below a baseline – nominally at zero volts. This means that accurate timing can be extracted from it even when the baseline voltage drifts.
In the early days of HD, the new equipment offered TLS and black and burst inputs for synchronization, but it was soon found that the old analog black and burst was preferred, already available and actually offered more accurate timing for 25p, 30p, 50i and 60i (but not suitable for other frame rates).
This has no strict technical meaning but is marketing hype. The ATSC says that all HD, 720P, 1080I and 1080P are all true HD, but the term has tended to be associated with 1080P often in advertising, but this is nothing official. Not to be confused with… TrueHD.
Ultra High Definition Television has two picture sizes, correctly referred to as UHD-1 (4K) and UHD-2 (8K), though more commonly known as 4K UHD and 8K UHD respectively. Both are standardized in ITU-R.BT. 2020.
The 4K UHD image is four times the area of 1920 HD at 3840 x 2160. There is now a choice of equipment for 4K UHD production and a number of programs have been produced in the format. 4K UHD TV screens are widely available; transmission trials have proved the delivery system using HEVC video compression via DVB.
What is now known as 8K UHD started life as Super-Hi vision in the laboratory at NHK in about 2001. The picture size is 7680 x 4320 – 16 times the area of 1920 HD. There are plans for transmission in Japan.
ITU-R BT.2020 describes framerates from 23.98 to 120 Hz with only progressive scans and a wider color gamut which can reproduce richer colors than HD. The 4K format has already been used for a number of broadcasts. For sport the 50 or 60 Hz framerate is popular. Even at lower rates the format produces very large quantities of data that require faster video links and more storage than HD. This requirement is four times larger with 8K.
Vestigial Sideband modulation – an established modulation technique which is used in the RF (radio frequency) transmission subsystem of the ATSC(1) Digital Television Standard. The 8-VSB system has eight discrete amplitude levels supporting a payload data rate of 19.28 Mb/s in a 6 MHz TV channel. There is also a high data rate mode – 16 VSB – designed for CATV (cable television) and supporting a payload of 38.57 Mb/s.
Things move on; E-VSB, Enhanced-VSB, was approved by ATSC in 2004 as an amendment to the A/53C DTV Standard as an optional transmission mode with additional forward error correction coding layers to help reception under weaker signal conditions. This was responding to the wishes broadcasters for more flexibility in DTV. E-VSB allows broadcasters to trade-off data rate for a lower carrier-to-noise threshold for some services, e.g. “fall back” audio, and targeted at receivers with indoor antennas, non-realtime transmissions of file-based information, and more.