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Glossary:
Jewel - Luminance
Glossary of CD and DVD related
technical terms and abbreviations in alphabetical order. |
J
Jewel Case: A plastic case commonly used for CDs and CD-ROMs, containing
the CD plus booklet.
Jitter: On a CD or DVD disc defines the percentage change in pit length
compared with its nominal value. If jitter is too high, pits can be
incorrectly read leading to data errors.
Joliet: Microsoft's extension to the ISO 9660 file system to handle long
filenames which are part of the features of Windows 95.
JPEG: ISO/CCITT Joint Photographic Experts Group, which has defined a
high-quality compression standard for still pictures using a DCT
algorithm.
Key: A binary code which is assigned a
unique value for encrypting data for security purposes. The key is
usually also encrypted so that it can accompany the encrypted data but
only allow the receiving device to decrypt it.
Key2audio: A CD audio copy protection
system developed by Sony DADC.
L
Lacquering: All CDs after metallising are protected with a lacquer by
spin coating.
LASER: Light Amplification by Stimulated Emission of Radiation; a means
of generating coherent light which can be focussed to a very small spot
size and ideal for reading compact discs, in laser beam recording and
for writing CD-R discs.
Layer 0: The lower, semi-reflective layer of a dual layer (DVD-9) disc.
Layer 1: The upper, fully reflective layer of a dual layer (DVD-9) disc.
Layer 1 can be Parallel Track Path (which starts at the ID) or Opposite
Track Path (which starts above where the Layer 0 program area ends) to
allow seamless playing from Layer 0 to Layer 1.
LBR: Laser Beam Recorder used in glass mastering CD and DVD discs. A
glass master disc, covered with a thin photo-resist coating is exposed
by the laser in a laser beam recorder where pits will be formed in the
final discs. The photo-resist is then developed and metallised with
Nickel. Stampers used in the moulding of CDs and DVDs are then
electroformed from the metallised glass master, which can then be
recycled and re-used.
Lead-in: The starting area of a CD or DVD or of each session of a
multisession CD. For a CD it contains the Table of Contents (TOC). For a
DVD it contains information describing the contents of the disc and the
type of disc.
Lead-out: The last area of a CD or session of a multisession disc or a
DVD, immediately after the program area.
Letter-box: A method for displaying wide screen video on a conventional
TV by adding black bars to the top and bottom so that the full width of
the image is seen.
LFE: Low Frequency Effects channel eg as contained in the .1 channel of
5.1 Dolby Digital surround sound audio on a DVD-Video disc.
Locales: The name for regions of the world defined in the DVD-Video
specification. Six regions are defined including 1: N America; 2: Europe
and Japan; 3: Australia, South Africa etc
Lossless Compression: A data compression process that ensures that the
original data is exactly recoverable. An example is MLP compression for
DVD-Audio.
Lossy Compression: A data compression process in which the original data
is not completely recoverable. For video or audio compression the lost
data is usually either redundant or does not significantly impair the
result. MPEG-2 is a lossy compression system.
LPCM: Linear PCM, one of the audio coding formats for DVD-Video.
Luminance: The intensity of a video signal usually represented by the
letter Y. The other signals are U & V (colour difference).
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