IDTVIntegrated 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 1080 x 1920 HD. In this case processing is included to re-size the pictures to fit the screen. See also: IRD, Table 3
IEEE 802.3 Standard that defines wired Ethernet. See: grouper.ieee.org/ groups/802/3/index.html
IEEE 1394 (a.k.a. FireWire, I-Link) A standard for a peer-to-peer serial digital interface which can operate at 100, 200, 400 or 800 Mb/s. IEEE 1394a specifies working up to 400 Mb/s, typically over copper cables up to 4.5 meters in length with six-pin connectors. Consumer devices use a four-pin connector. Extenders increase the maximum distance from 4.5 meters on copper cables up to about 100 meters on glass optical fiber. IEEE 1394b extends both data rate and distance: up to 1.6Gb/s on shielded twisted pair cable up to 4.5m, and has architecture to support 3.2Gb/s over 100m on optical fiber. See also: Asynchronous, Isochronous Website: www.1394ta.org
I-frame only (a.k.a. I-only) A video compression scheme in which every frame is intra-frame (I-frames) compressed, i.e. individually defined and does not depend on any other frames for decoding. There are no P (predictive) or B (bi-directional) frames in such compression schemes. This is considered preferable for studio use as edits can be made on any frame boundaries without necessarily involving processing. All DV compression is I-frame only. MPEG-2 and MPEG-4 with a GOP of 1 is I-frame only. For example these are used in Sony's IMX VTRs and HDCAM SR respectively. JPEG 2000 is I-frame only. See also: Cut (edit), D11, GOP, Intra-frame (compression), JPEG 2000, MPEG-2, MPEG-4
I-Link See IEEE 1394
Illegal colors Colors that lie outside the limits, or gamut, of a particular color space. These can be generated when moving images from one color space to another, as they all have different boundaries, or as the result of color processing. For example, removing the luminance from a high intensity blue or adding luminance to a strong yellow in a paint system may well send a subsequent PAL or NTSC coded signal too high or low - producing at least inferior results and maybe causing technical problems. Out-of-gamut detectors can be used to warn of possible problems and correction is also available. Some broadcasters reject material with illegal colors.
IMX See D10
InfiniBand InfiniBand defines an input/output architecture that can connect servers, communications infrastructure equipment, storage and embedded systems. It can achieve data transfers up to 120GB/s over copper and optical fiber connections, with the benefits of low latency and only requiring a low processing overhead. It is used in many data centers, high-performance computer clusters and embedded applications that scale from two nodes up to a single cluster that interconnect thousands of nodes.
ING IT-News Gathering - coined by Panasonic to highlight their use of Secure Data (SD) memory as the in-camera media store for their DVCPRO P2 (P2 Cam) news cameras. See also: DV, ENG
In-server editing Editing at a workstation which directly edits material stored in a server. For this the workstation does not need large-scale video and audio storage but depends totally on the server store. The arrangement allows background loading of new material, via several ports if required, and playout of finished results, while avoiding any need to duplicate storage or transfer material to/from the workstation and allowing any number of connected workstations to share work. The efficiency of in-server editing allows fast throughput and is specially attractive to news as well as to post production where jobs can be instantly available in rooms, or move between rooms. This depends on using a server that can act as an edit store and perform reliable video replay and record. It also requires a powerful interface to the edit workstation. See also: Delta editing
Interactive Television (iTV) 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.
Inter-frame (compression) Compression which involves more than one frame. Inter-frame compression compares consecutive frames to remove common elements and arrive at 'difference' information to describe frames between I-frames. MPEG-2 and MPEG-4 use two types of inter-frame processed pictures - the 'P' (predictive) and 'B' (bi-directional) frames. As 'P' and 'B' frames are not complete in themselves but relate to other adjacent frames, they cannot be edited independently. See also: Cut edit, MPEG-2, MPEG-4
Interlace Factor The reduction in vertical definition during vertical image movement due to interlaced (rather than progressive) scans. Experimentally it is found to be about 30%. Note that, when scanning film frame-per-frame (i.e. 24 or 25fps - not 3:2 pull-down to 60fps), or a succession of electronic frames each representing a single snapshot in time, there is no vertical movement between fields and the Interlace Factor has no effect. See also: 24PsF
Interlace (scan) Method of scanning lines down a screen (vertical refresh) - as used in most of today's television broadcasts and originally designed to suit the needs of CRT displays and analog broadcasts. Interlace is indicated in television scan formats by an 'I' e.g. 1080I, etc. Each displayed picture comprises two interlaced fields: field two fills in between the lines of field one. One field displays odd lines, then the other shows even lines. For analog systems, this is the reason for having odd numbers of lines in a TV frame e.g. 525 and 625, so that each of the two fields contain a half-line, causing the constant vertical scan to place the lines of one field between those of the other. The technique greatly improves the portrayal of motion and reduces picture flicker without having to increase the picture rate, and therefore the bandwidth or data rate. Disadvantages are that it reduces vertical definition of moving images by about 30% (see Interlace Factor) of the progressive scan definition and tends to cause some horizontal picture detail to 'dither' - causing a constant liveliness even in still pictures. Interlaced video requires extra care for processing, such as in DVE picture size changes, as any movement between fields has to be detected if the higher-quality frame-based processing is used. Also frame freezes and slow motion need 'de-interlace' processing. There is continuing debate about the use of interlaced and progressive scans for DTV formats. This has intensified now that the increasingly popular panel displays are all progressive. See also: Interlace Factor, Progressive
Internegative As a part of the chemical lab film intermediate process internegatives are created by contact printing from interpositives. These very much resemble the cut negative. The stock is the same as for interpositives: slow, very fine grain with a gamma of 1, and the developed film is orange- based. To increase numbers, several internegatives are copied from each interpositive. These are then delivered to production labs for large scale manufacture of release prints. See also: Film basics (Tutorial 2)
Interocular distance (Stereoscopic) The distance between the centers of the lenses of two recording cameras. A typical distance would be 63.5 mm (approximating average adult eye spacing). The term 'interaxial' is sometimes also used interchangeably with 'interocular' (when referring to eyesight, 'interpupillary' is often used).
Interoperability The ability of systems to interoperate - to understand and work with information passed from one to another. Applied to digital media this means video, audio and metadata from one system can be used directly by another. Digital signals may be originated in various formats and subjected to different types of compression so care is needed to maintain interoperability.
Interpositive This is a first part of the chemical lab intermediate process where a positive print of film is produced from the cut (edited) camera negative. Interpositives are made by contact printing onto another orange-base stock. In order to preserve as much detail as possible from the negative, including its dynamic range, interpositive material is very fine grain, slow and has a gamma of 1. During the copying process, grading controls are used to position the image density in the center of the interpositive material's linear range. As a part of the process of going from one camera negative to, possibly, thousands of prints, a number of interpositives are copied from the negative. See also: Film basics (Tutorial 2)
Interpolation (spatial) Defining the value of a new pixel from those of its near neighbors. When re-positioning or re-sizing a digital image, for dramatic effect or to change picture format, more, less or different pixels are required from those in the original image. Simply replicating or removing pixels causes unwanted artifacts. For far better results the new pixels have to be interpolated - calculated by making suitably weighted averages of adjacent input pixels - to produce a more transparent result. The quality of the results will depend on the techniques used (bi-cubic is generally accepted as being good) and the number of pixels (points) taken into account (hence 16-point interpolation), or area of original picture, used to calculate the result. See also: Anti-aliasing, Interpolation (temporal), Sub-pixel
Interpolation (temporal) Interpolation between the same point in space (pixel) on successive frames. It can be used to provide motion smoothing and is extensively used in standards converters to reduce the judder caused by field rate changes - such as between 50 and 60 Hz. The technique can also be adapted to create frame averaging for special effects and slow motion. Various qualities of processing are used. It can be very complex, attempting to work out how each element in successive pictures is moving in order to synthesis 'between' images.
Intra-frame (compression) Compression that occurs within one frame. The compression process only removes redundant and visually less significant information from within the frame itself. No account is taken of other frames. JPEG and the 'I' framesof MPEG-2 are coded in this way and use DCT. In the MPEG-2 sequence only I-frames can be edited as they are only independent frames. See also: DCT, I-frame only, JPEG, MPEG-2
I-only See: I-frame only
IP Internet Protocol is the de facto standard for networking and is the widest used of the network protocols that carry the data and lie on top of physical networks and connections. Besides its internet use it is also the main open network protocol that is supported by all major computer operating systems. IP, or specifically IPv4, describes the packet format for sending data using a 32-bit address to identify each device on the network with four eight-bit numbers separated by dots e.g. 192.96.64.1. Each IP data packet contains a source and destination address. There is now a move toward IPv6 which brings, among many other enhancements, 128-bit addressing - enough for over 6,000 billion devices and relieving IPv4's address shortage. Above IP are two transport layers. TCP (Transmission Control Protocol) provides reliable data delivery, efficient flow control, full duplex operation and multiplexing (simultaneous operation with many sources and destinations). It establishes a connection and detects corrupt or lost packets at the receiver and re-sends them. Thus TCP/IP, the most common form of IP, is used for general data transport but is slow and not ideal for video. UDP (User Datagram Protocol) uses a series of 'ports' to connect data to an application. Unlike the TCP, it adds no reliability, flow-control or error-recovery functions but it can detect and discard corrupt packets by using checksums. This simplicity means its headers contain fewer bytes and consume less network overhead than TCP, making it useful for streaming video and audio where continuous flow is more important than replacing corrupt packets. There are other IP applications that live above these protocols such as File Transfer Protocol (FTP), Telnet for terminal sessions, Network File System (NFS), Simple Mail Transfer Protocol (SMTP) and many more. Website: www.ipv6forum.com
IP Datacast Forum (IPDC) The IPDC Forum was launched in 2002 to promote and explore the capabilities of IP-based services over digital broadcast platforms (DVB and DAB). See also: IP over DVB Website: www.ipdc-forum.org
IP over DVB 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. See also: IP Datacast Forum, Data carousel
IPTV Internet Protocol Television is the use of the IP packetized data transport mechanism for delivery of streamed realtime television signals across a network.
IRD Integrated Receiver Decoder. A device that has both a demodulator and a decoder (e.g. for MPEG-2) built in. This could be a digital television set or a digital set-top box. See also: IDTV
ISDB Integrated Services Digital Broadcasting - standard for digital broadcasting used in Japan. ISDB has many similarities to DVB including OFDM modulation for transmission and the flexibility to trade signal robustness against delivered data rate. See also: COFDM, DiBEG, DVB Website: www.dibeg.org
ISO International Standards Organization. An international organization that specifies international standards, including those for networking protocols, compression systems, disks, etc. See: Directory Website: www.iso.ch
Isochronous A form of data transfer that carries timing information with the data. Data is specified to arrive over a time window, but not at any specific rate within that time. ATM, IEEE 1394 and Fibre Channel can provide isochronous operation where links can be booked to provide specified transfer performance. For example, 60 TV fields can be specified for every second but their arrival may not be evenly spread through the period. As this is a guaranteed transfer it can be used for 'live' video but is relatively expensive on resources. See: ATM, Asynchronous, Fibre Channel, IEEE 1394, Synchronous
ITU International Telecommunications Union. The United Nations regulatory body covering all forms of communication.The ITU sets mandatory standards and regulates the radio frequency spectrum. ITU-R (previously CCIR) deals with radio spectrum management issues and regulation while ITU-T (previously CCITT) deals with telecommunications standardization. Suffix BT. denotes Broadcasting Television. See: Directory Website: www.itu.ch
ITU-R BT.601 This standard defines the digital encoding parameters of SD television for studios. It is the international standard for digitizing component television video in both 525 and 625 line systems and is derived from SMPTE RP125. ITU-R BT.601 deals with both color difference (Y, R-Y, B-Y) and RGB component video and defines sampling systems, RGB/Y, R-Y, B-Y matrix values and filter characteristics. It does not actually define the electro-mechanical interface - see ITU-R BT. 656. See also: 13.5 MHz, 4:2:2
ITU-R BT.656 The international standard for interconnecting digital television equipment operating to the 4:2:2 standard defined in ITU-R BT.601. It defines blanking, embedded sync words, the video multiplexing formats used by both the parallel (now rare) and serial interfaces, the electrical characteristics of the interface and the mechanical details of the connectors.
ITU-R BT.709 In 2000, ITU-R BT.709-4 recommended the 1080 active line standard for 50 and 60 Hz interlace scanning with sampling at 4:2:2 and 4:4:4. Actual sampling rates are 74.25 MHz for luminance Y, or R, G, B and 37.125 MHz for color difference Cb and Cr, all at 8 bits or 10 bits, and these should be used for all new productions. It also defines these 1080-line square-pixel standards as a common image formats (CIF) for international exchange. The original ITU-R BT.709 recommendation wasfor 1125/60 and 1250/50 (1035 and 1152 active lines) HDTV formats defining values and a '4:2:2' and '4:4:4' sampling structure that is 5.5 times that of ITU-R BT.601. Note that this is an 'expanded' form of 601 and so uses non-square pixels. See also: Common Image Format IJ ITU-R/BT.799, Dual link
iTV See: Interactive Television