DVB-SH, has been agreed and awaits standardization by ETSI. It can deliver IP-based media content and data to handheld terminals – phones and PDAs and operates below 3 GHz, typically in the S-band. Terrestrial gap fillers can provide any missing coverage where there is no line-of- sight path to the satellite.
DVB-S (1995) 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) will probably be used for all future 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 DVS-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 30 percent.
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DVB-T 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), which enables it to operate effectively in very strong multipath environments. This means DVB-T can operate an overlapping network of transmitting stations with the same frequency. In the areas of overlap, the weaker of the two received signals is rejected. Where transmitters carry the same programming the overlapping signals provide an area of more reliable reception, known as a signal-frequency network. The DVB digital TV standard is predominant around the world. Notable exceptions are ATSC in the USA, ISDB in Japan, DMB-T/H (Digital Multimedia Broadcast- Terrestrial/Handheld) in China, and T-DMB in South Korea.
DVB-T2 The new extension of the television standard DVB-T, issued by the DVB Group and aims to deliver a minimum 30 percent increase in payload under similar channel conditions. This system transmits compressed digital audio, video, and other data in “physical layer pipes” (PLPs), using OFDM modulation with concatenated channel coding and interleaving. It is currently broadcasting in parts of the UK under the brand name Freeview HD.
DVB over IP Refers to delivery of digital television services (DVB) to homes over broadband IP networks. This could be supplied via cable or, possibly over copper telephone lines using high-speed DSL and the supplier could then achieve the ‘triple play’ – bundling voice (over-IP) telephone as well as Internet with the television service. This has great potential for interactive television as it includes a built-in fast return link to the service provider. See also: COFDM, IP, IP over DVB Website:
www.dvb.org
DVCAM See: DV
DVCPRO See: DV
DVD Digital Versatile Disk – a high-density development of the compact disk. It is the same size as a CD, 12 cm diameter, but stores upwards of 4.38 GB of actual data (seven times CD capacity) on a single-sided, single-layer disk. DVDs can also be double-sided or dual-layer – storing even more data. The capacities commonly available are: DVD-5 Single-side, single-layer 4.38 GB DVD-9 Single-side, dual-layer 7.95 GB DVD-10 Double-sided, single-layer 8.75 GB DVD-18 Double-sided, dual-layer 15.9 GB DVD-5 and DVD-9 are widely used. However the double-sided disks are quite rare, partly because they are more difficult to make and they cannot carry a label. There are various types of DVD including: DVD-R – recordable DVDs with a data capacity of 4.38 GB are popular and low priced. DVD+R – dual layer recordable DVDs with a total capacity of two DVD-Rs. DVD-RAM – re-recordable DVD, re-use up to around 100,000 times. Capacity of 4.38 GB (single-sided). Some new camcorders use these – they offer instant access to shot material and record loop features – useful when waiting to record an event, like a goal, to happen. At home it provides a removable media alternative to VHS. A particular feature is that it can record and replay at the same time.
DVD-Video
Combines the DVD with MPEG-2 video compression, with multichannel audio, subtitles and copy protection capability. Multi-channel audio DVD- Video supports PCM, MPEG and Dolby Digital audio, for anything from mono, stereo, Dolby Surround to 5.1 channels. Digital Theatre Sound (DTS) and Sony Dynamic Digital Sound (SDDS) are options. Up to eight separate audio streams can be supported, allowing multiple languages, audio description, director’s commentary, etc. For example, a release may have 5.1 Dolby Digital English, two-channel Dolby Digital Spanish with Dolby Surround, and mono French. Region coding Disks can be region- coded and so only play in a particular region (as defined in the player), a set of regions or be ‘code-free’. The region numbers are: 1. Canada, US, US Territories 2. Japan, Europe, South Africa, Middle East (including Egypt) 3. Southeast Asia, East Asia (including Hong Kong) 4. Australia, New Zealand, Pacific Islands, Central America, South America, Caribbean 5. Former Soviet Union, Indian Subcontinent, Africa (also North Korea, Mongolia) 6. China See also: HD DVD, Blu-ray Disc, Dolby Digital, Dolby Surround, MPEG-2, MPEG-4
DVE Digital Video Effects (systems). These have been supplied as separate machines but increasingly are being included as an integral part of systems. The list of effects varies but will always include picture manipulations such as zoom and position and may go on to rotations, 3D perspective, page turns, picture bending and curls, blurs, etc. Picture quality and control also vary widely depending on the processing techniques used. See also: Axis, Global D DVTR DVTR – Digital Video Tape Recorder. Sony showed the first DVTR for commercial use in 1986, working to the ITU-R BT.601 component digital video standard and the associated D1 standard for DVTRs. All modern tape recorders are digital and use some form of compressed component video. See also: Betacam SX, D5, D9, DV, DVCPRO, HDCAM
Dynamic range
For images – the measurement of the range of brightness in a scene expressed as a ratio or the Log10 of the ratio. Typically a lighting cameraman will try to keep a scene to less than 40:1 (Log = 1.6) to avoid loss of detail in the print. A 100:1 (Log = 2) contrast range in the scene is a typical maximum. See also: Cineon file DE EBU European
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GLOSSARY OF TERMS
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