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- LANC
- (See CONTROL-L)
- LAND
- A non-indented area on an optical medium such as a CD or DVD disc. For reading purposes, a directed laser beam is either reflected off the land or absorbed by indentations called pits. Using various algorithms, the reflections are converted into 0 or 1 data bits. (See also PIT)
- LASER (Light Amplification by Stimulated Emission of Radiation)
- A means of generating coherent light which can be accurately focused to a very small spot size, ideal for reading or writing optical disc media.
- LASERDISC
- 12" consumer optical disc format used for the storage of audio and video signals. The laserdisc utilizes a high quality analog video signal capable of >400 lines of horizontal resolution as well as analog and/or digital audio tracks. Both CAV and CLV recording methods have been employed in the making of these discs over the years. The laserdisc has all but been replaced by the all digital DVD format.
- LATENCY
- The time lag between audio entering a computer, being routed through software and hardware, and finally appearing at the output.
- LAVALIERE MICROPHONE
- Small microphone worn around the neck or clipped to clothing.
- LCD (Liquid Crystal Display)
- A screen for displaying text/graphics based on a technology called liquid crystal, where minute currents change the reflectiveness or transparency of the screen. The advantages of LCD screens are: very small power consumption (can be easily battery driven) and low price of mass produced units. Its disadvantages presently include narrow viewing angle, somewhat slower response time, invisibility in the dark unless the display is back-lit, difficulties displaying true colors and resolution limitations.
- LEAD-IN
- An area at the beginning of each session on a recordable compact disc which is left blank for the session’s Table of Contents or TOC. The lead-in is written when a session is closed, and takes up 4500 sectors on disc (1 minute, or roughly 9 megabytes). The lead-in also indicates whether the disc is multisession by giving, if the disc is not closed, the next recordable address on the disc.
- LEAD-OUT
- An area at the end of a session which indicates that the end of the data has been reached; there is no actual data written in the lead-out. The first lead-out on a disc is 6750 sectors (1.5 minutes, about 13 megabytes) long; any subsequent lead-outs are 2250 sectors (0.5 minute, about 4 megabytes) .
- LFE (Low Frequency Effects)
- Name given to the dedicated subwoofer channel in Dolby Digital and DTS audio formats.
- LINEAR EDITING
- Editing using media like tape, in which material must be accessed in order (e.g., to access scene 5 from the beginning of the tape, one must proceed from scene 1 through scene 4). (See NONLINEAR EDITING)
- LINE COMPENSATION
- Use of a video line amplifier to pre-compensate for high frequency video signal transmission losses resulting from long distance cable runs (several hundred meters) by boosting those signal frequencies most effected. Without such compensation, deterioration is manifested as loss of fine details and color distortion.
- LINKED MULTISESSION
- A disc containing more than one recorded session, in which all (or selected) data from the various sessions can be seen as if it had all been recorded in a single session. (See MULTISESSION)
- LOAD RESISTANCE
- The impedance or resistance (load) that a cable places on a signal being transmitted through it. In the case of a high frequency signal, signal-to-cable matching is essential to prevent signal deterioration.
The cable should be terminated by a specific load resistance, usually 50 or 75 ohms. Improper cable loading results in signal distortion, ghost images, color loss and other adverse phenomena. Most video inputs have the proper termination built in.
- LOGICAL BLOCK
- The smallest addressable space on a disc. Each logical block is identified by a unique Logical Block Number (LBN), assigned in order starting from 0 at the beginning of the disc. Under the ISO 9660 standard, all data on a CD is addressed in terms of Logical Block Numbers.
- LOGICAL FORMAT
- A file system such as ISO 9660 translates the sector-by-sector view of a compact disc into a virtual "tree" of directories and files, which makes it easier for both humans and computers to use the information on the disc. UDF is another example of a file system which can be used to write CDs.
- LOOPING
- A term used to describe the chaining of a video signal through several video devices (distribution amplifiers, VCRs, monitors, etc.).
A VCR may be hooked up to a distribution amplifier which is supplied with a video input connector and a loop output connector. When a signal is fed to the distribution amplifier, it is also fed unprocessed to the loop output connector (parallel connection) on the distribution amplifier. In turn, the same signal is fed to another device which is attached to the first one and so on. Thus a very large number of VCRs or other video devices can be looped together for multiple processing.
- LOSSY
- Refers to data compression techniques in which some amount of data is sacrificed in the name of file size reduction. Lossy compression technologies attempt to eliminate redundant or unnecessary information. Examples of lossy compression formats are the photo JPEG format, audio Dolby Digital format and video MPEG formats.
- LTC (Longitudinal Time Code)
- SMPTE time code standard usually recorded onto the linear audio track of a VCR or fed to a clapslate for later syncing with video.
- LUMINANCE
- That part of a video signal relating to the degree of brightness at any given point in the video image. A video signal is comprised of luminance, chrominance (color information) and sync. If luminance is high, the picture is bright and if low, the picture is dark. Changing the chrominance does not affect the brightness of the picture.
- LUMINANCE NOISE
- Noise which manifests itself in a video picture as white snow, typically caused by one of the following situations:
- Low signal level due to poor lighting conditions
- Poor video signal processing
- Low quality videotapes
- Excessively long video cables used without pre-compensation
- Dirt on the video recorder heads which interferes with reading and writing
- Over-enhancement of the video signal
- LUX
- A measurement of light intensity, which is used in photography for the comparison of camera sensitivities. (1 Footcandle = 10.76 Lux)
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