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I (In Phase) Signal

One of two color difference signals in the NTSC system. The other signal is the Q (Quadrature) signal.

I Frames

One of the three types of frames that are used in MPEG-2 coded signals. These contain data to construct a whole picture as they are composed of information from only one frame (intraframe). The original information is compressed using DCT.
See also: B frames, P frames, MPEG.


United Kingdom statutory authority responsible for regulating domestic independent broadcasters, both technically and legally.

IBOC - In In-Band, On Channel"  For example:  In the existing FM Band, or In the existing AM Band

This is a new standard of digital transmission. There is both AM-IBOC and FM-IBOC.


Interface Control Document - Describes protocol for exchanging data between systems (i.e. headers, field order, codes, etc.)


A graphic associated with a computer function to be performed; a term referring to symbols used for computer commands on computers equipped with a Graphic User Interface. (See GUI).

ID (Identification)

1. This usually refers to the station ID.  By FCC regulations, all stations must identify visually and or aurally once every hour.  The ID must contain the station’s call sign or letters and city of license.  All IDs must be logged in the official operating log. 2. A unique sequence of characters used to identify an event or tape cassette (box).

IEC (International Electrotechnical Commission)

IEEE P1394 (FireWire)

A low-cost digital interface originated by Apple Computer as a desktop LAN and developed by the IEEE P1394 working group. Can transport data at 100, 200, or 400 Mbps.
Serial Bus Management provides overall configuration control of the serial bus in the form of optimizing arbitration timing, guarantee of adequate electrical power for all devices on the bus, assignment of which IEEE P1394 device is the cycle master, assignment of isochronous channel ID, and notification of errors.
There are two types of IEEE P1394 data transfer: asynchronous and isochronous. Asynchronous transport is the traditional computer memory-mapped, load and store interface. Data requests are sent to a specific address and an acknowledgment is returned.
In addition to an architecture that scales with silicon technology, IEEE P1394 features a unique isochronous data channel interface. Isochronous data channels provide guaranteed data transport at a pre-determined rate. This is especially important for time-critical multimedia data where just-in-time delivery eliminates the need for costly buffering.

IFS (Integrated Financial System)

The MEASAT billing system for spots and provider payment.

Image Intensifier

A device used in law enforcement, surveillance, and security applications that can amplify the image output signal of an imager, producing a usable picture in extremely low-light situations.

Image Map

Image Maps are user-defined areas of an image, also known as hot spots, which move a user from an image to an associated URL or page within a URL when clicked. Images may have more than one defined area; each with its own associated URL. The top of this page features an image map.

Image Processing

Techniques that manipulate the pixel values of an image to alter or improve image quality. Examples include brightness or contrast correction, color correction, changing size (scaling), or changing the shape of the image (warping).


An expression of the electrical resistance in a circuit that is the total opposition to electric current flow. Impedance is measured in Ohms (W). A standard video signal has an impedance of 75W.

Inner Coding

Punctured, convolutional coding scheme used for the DVB-S and DVB-T system specifications.


Bins in an LMS functioning as the cassette input area.  Cassettes placed in these bins by an operator are transferred by the LMS robot to internal, long-term storage bins within the system.

Input Jitter Tolerance

Peak-to-peak amplitude of sinusoidal jitter that, when applied to equipment input, causes a specified degradation of error performance.

Insert Edit

An electronic edit in which the existing control track is not replaced during the editing process. The new segment is inserted into program material already recorded on the video tape. Tapes are often "Striped" or "Blacked" for this purpose.  Also, the insertion of a segment into an already recorded series of segments on a videotape. Allows separate editing of video and audio tracks.


Individual commercial appearance on broadcast advertising schedule.

Intelligent Device Controllers (IDC)

Generic term for devices that directly control other devices typically by means of serial and/ or parallel control signals.


Involving the active participation of the user in directing the flow of the computer or video program. A system which exchanges information with the viewer, processing the viewer’s input in order to generate the appropriate response within the context of the program—as opposed to a linear program in which the viewer passively watches from beginning to end.

Interactive Graphics

1. An audiographic teleconferencing system which allows all sites to modify and change a commonly shared electronic diagram or graphic. 2. Computer graphics.

Interactive Media

1. Media which involves the viewer as a source of input to determine the content and duration of a message, permitting individualized program material. 2. A philosophy of media production designed to take maximum advantage of random access, computer-controlled videotape and videodisc players.

Interactive Video

The combination of microprocessors and video where the sequence of information is determined by the user’s response.


An electronic device which allows dissimilar components in a system to communicate. The connection between two devices, such as a computer and a peripheral, for example.

Interframe Coding

Data reduction based on coding the differences between a prediction of the data and the actual data. Motion compensated prediction is typically used, based on reference frames in the past and the future.


The pattern of two separate field scans when they join to form a complete video frame. As the video picture is transmitted, the first field picks up even-numbered scan lines, the second picks up odd-numbered ones. The two lace together to form a single, complete frame. (See “Field” and “Frame”).

The display of a video frame as two fields (odd scan line painted first, then even scan lines).

 Interlace Scanning

A method of scanning in which one-half the total lines (262.5) are scanned in one field (even-numbered lines), and the other half of the total number of lines are scanned in the next field (odd-numbered lines). Thus, adjacent lines of a complete picture (one-frame) belong to successive fields.

Interlace (scan)

Method of scanning lines down a screen - as used in today's television broadcasts. Each displayed picture comprises two interlaced fields: field two fills in between the lines of field one. For analogue systems, this is the reason for having odd numbers of lines in a picture eg 525 and 625, so that each field contains a half-line, causing the constant vertical scan to place the lines of
one field between those of the other.

The technique improves the portrayal of motion and reduces picture flicker without having to increase the picture rate (and therefore the bandwidth/data rate). Disadvantages are that it reduces vertical definition of moving images to about 70% (see Interlace Factor) of the progressive scan definition and tends to cause horizontal picture detail to 'dither'.

There is continuing debate about the use of interlaced and progressive scans for DTV formats.

              See also: Interlace Factor, Progressive

Interlace Factor

The reduction in vertical definition during vertical image movement due to
interlaced (rather than progressive) scans. Typically this is assumed to be
30%, and is in addition to the Kell Factor (another 30% reduction), making
an overall reduction of 50%. Note that, when scanning film frame-per-frame
(ie 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.


The RS-protected transport packets are reshuffled byte by byte by the 12-channel interleave.  Due to this reshuffle, what were neighboring byes are now separated by at least one protected transport packet, i.e., are at least 204 bytes apart from each other.  The purpose of this is the burst error control for defective data blocks.

 Interline Transfer (IT) Device

A CCD that employs light-shielded structures called vertical registers which are mounted next to individual pixel sensors to facilitate charge transfer. IT devices are simpler to manufacture and are, therefore, less costly than FT or FIT devices. IT sensors are used on lower-cost broadcast cameras and most industrial and consumer cameras.


Color Negative made from an Inter-positive, from which the Release Prints are made. The Inter Negative is composited and color graded (color timed), and of low contrast making it a good choice for telecine processes.


A color master positive print, on negative stock. Used as the intermediate stage in the production of Duplicate Negatives.  Inter-Positives are graded low contrast masters and therefore very suitable for Telecine Transfer.


Unwanted additional energy in a signal and unwanted contributions from less informed individuals.


A process in which the picture is split into two fields by sending all the odd numbered lines to field one and all the even numbered lines to field two. One video frame, is made up of two interlace fields. This was necessary in the early days of TV when there was not enough bandwidth to send a complete frame fast enough to create a non-flickering image. 


General term for color masters and dupes.


Occurring infrequently. Difficult to describe or to prove and therefore extremely annoying.


Originally designed by the U.S. Defense Department so that a communication signal could withstand a nuclear war and serve military institutions worldwide, the Internet was first known as the ARPAnet. The Internet is system of linked computer networks, international in scope, that facilitates data communication services such as remote login, file transfer, electronic mail and newsgroups. The Internet is a way of connecting existing computer networks that greatly extends the reach of each participating system.


In digital video, the creation of new pixels in the image by some method of averaging the values of neighboring pixels. This is necessary when an image is digitally altered, such as when the image is expanded or compressed.  Also inferring a point which does not actually exist by averaging real points near it, either in space or time. Used extensively in digital effects devices and standards converters.

 Inter-Spot Gap

The interval between two spots, usually filled by Color Black, and used to determine the pacing of a material playout sequence.


Any short form material that goes between cuts in a larger program or between programs themselves.  These are usually spots, PSAs, promos, etc.

 Intra-coded Pictures or I-Pictures or I-Frames

Pictures that are coded using information present only in the picture itself and not depending on information from other pictures.  I-pictures provide a mechanism for random access into the compressed video data.  I-pictures employ transform coding of the pel blocks and provide only moderate compression.


A private network inside a company or organization that uses the same types of software that you would find on the public Internet, but is only for internal use.

Intrinsic Jitter

Jitter at a device's output in the absence of input jitter.


Input/output. Typically refers to sending information or data signals to and from devices.

IP Address

Internet Protocol Address. A numeric address that is given to servers and users connected to the Internet.

 I, P and B Pictures

Intra-coded picture (I), predicted pictures (P) and bi-directional predicted pictures (B).

 IPPV (Impulse Pay-Per-View)

The ability to order a movie advertised in the EPG, directly through the IRD (Interactive Receiving Decoder).


Internet Relay Chat. A live chat area of the Internet in which real-time conversations among two or more people take place via special software.  Each specific IRC channel begins with a # and is dedicated to a different area of interest. IRC is considered another part of the technology of the Internet the same way FTP, Telnet and the Web are.

 IRD (Integrated Received Decoder)

The (consumer set-top box) for reception and decoding of subscription A/V/data services. Decodes the signal downlinked from the satellite. Unscrambles programming provided the viewer is entitled. Also capable of communication with the SMS if implemented. Allows viewer to interact with the facility to request a PPV event.


The Institute of Radio Engineers.  An organization defining the IRE unit equal to 1/140th of the peak-to-peak amplitude of a video signal.  Typically for baseband video, 1 volt =140 IRE and 7.14 mV = one IRE.  On a waveform monitor, each vertical mark on the graticule is 10 IRE.


An aperture in camera lenses which controls the amount of light passing through the lens to reach the imager. The iris is required to compensate for changing lighting conditions.

 ISDN  (Integrated Services Digital Network)

Allows data to be transmitted at high speed over the public telephone network. ISDN operates from the Basic Rate of 64 kbits/sec to the Primary Rate of 2 Mbps (usually called ISDN-30 as it comprises 30 Basic Rate channels). Most of the Western world currently has the capability to install ISDN-2 with 128 kbps and very rapid growth is predicted for ISDN generally. In the television and film industries, audio facilities are already using it. The cost of a call is usually similar to using a normal telephone.
Nominally ISDN operates internationally, but there are variations in standards, service and ISDN adapter technologies. Some operators in the USA use a similar system, Switch 56 (56 kbits/sec and upwards), although the availability of ISDN is becoming wider.

A CCITT standard for integrated transmission of voice, video, and data. Bandwidths include basic rate (144 kbps) and primary rate (1.544 and 2.048 Mbps.)

 ISO (International Organization of Standardization)

 ISO 646

An international character set standard, of which ASCII is a subset.


Internet Service Provider. A company that provides access to the Internet. Before you can connect to the Internet you must first establish an account with an ISP.

 ITU (International Telecommunication Union)

International Telecommunications Union. An international broadcast standards committee that replaced the CCIR. Place des Nations, CH-1211 Geneva 20, Switzerland. Tel: 011-41-22-730-5111. Fax: 011-41-22-733-7256. Email: itumail@itu.int. Internet: www.itu.ch.

 ITU-R 601

See: ITU-R BT.601-2.

 ITU-R BT.601-2:

Formerly known as CCIR 601. An international standard for component digital television from which was derived SMPTE 125M (was RP-125) and EBU 3246E standards. This International Telecommunications Union (ITU) recommendation defines the sampling systems, matrix values, and filter characteristics for both Y, B-Y, R-Y and RGB component digital television.
ITU-R BT.656 Formerly known as CCIR 656. The physical parallel and serial interconnect scheme for ITU-R BT.601-2 (CCIR 601). ITU-R BT.656 defines the parallel connector pinouts as well as the blanking, sync, and multiplexing schemes used in both parallel and serial interfaces. Reflects definitions in EBU Tech 3267 (for 625-line signals) and in SMPTE 125M (parallel 525) and SMPTE 259M (serial 525).

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