5.1 - AVI
Glossary of CD and DVD related
technical terms and abbreviations in alphabetical order.
3/2 Pulldown: A technique (3/2 pulldown) for converting 24 fps film
to 30 fps NTSC video by adding fields.
4C Entity: The group of companies (IBM, Intel, MEI and Toshiba)
that developed copy protection for DVD etc. The 4C Entity licenses CPPM,
CPRM and Verance watermarking.
5.1: A surround sound format comprising 5 full bandwidth channel
(left, centre, right, left surround and right surround) plus a low
frequency effects channel (LFE).
a_characters: The ISO 9660 character set used in the Volume
Descriptors and comprising 'A' to 'Z', '0' to '9', space plus symbols.
A-Time: Absolute-timecode for CDs, contained in the subcode Q-channel as
minutes, seconds and frames measured from the beginning of the disc.
AC-3: Dolby's 5.1 channel surround sound digital audio system,
specified for DVD-Video discs. It is now referred to as Dolby Digital.
ACP: Macrovision’s Analogue Copy Protection system for DVD-Video,
developed and patented by Macrovision. It comprises two elements:
Automatic Gain Control (AGC) and Colorstripe. ACP is supported by
most DVD players, and causes VCRs to make distorted copies, with no
ADPCM: Adaptive Differential Pulse Code Modulation is an audio encoding
compression technique that encodes the difference between the predicted
value of the signal instead of the absolute value of the original waveform
so that the compression efficiency is improved. This difference is usually
small and can thus be encoded in fewer bits than the sample itself. ADPCM
is used in PC sound cards, on CD-i and CD-ROM XA discs.
AFM: Atomic Force Microscopy, a technique for measuring the
topology of 'bumps' on a CD or DVD stamper, to ensure that the mastering
and electrofoming processes are creating stampers that will result in good
Ag: The chemical symbol for Silver, used as the reflective layer of
CD-R discs (as a replacement for gold). A silver alloy is also used as the
semi-reflective layers on dual layer DVD discs.
AGC: Automatic Gain Control, which is used in Macrovision’s
Analogue Copy Protection (ACP), which causes VCRs to distort the
video so that the copy is unviewable.
Al: The chemical symbol for Aluminium, used for the reflective
layer on CD and DVD discs.
Album: One side of a DVD-Audio disc, containing Groups and Tracks.
Album ID: The unique identifier for a DVD-Audio album, necessary
for a CPPM-protected disc.
Aliasing: A form of image distortion associated with signal
sampling at low resolutions. The result is that diagonal lines appear
stepped (like a staircase).
Amaray Case: A plastic clamshell type case designed for DVD discs
to differentiate them from CDs and to protect them. It is similar to
clamshell cases used for VHS cassettes but is wider and thinner.
Analogue: The representation of numerical values by physical variables
such as voltage, current, etc. Analogue devices are characterized by dials
and sliding mechanisms.
Analogue Video: A video signal that represents an infinite number
of smooth gradations between given video levels. By contrast, a digital
video signal assigns a finite set of levels. Analogue signals are prone to
the effects of noise, but digital signals are less affected by noise.
Anamorphic: A term used to describe the representation of a
wide-screen video image by squeezing it horizontally to fit into a
conventional 4:3 aspect ratio for purposes of storage and transmission.
The image is stretched back to wide screen (usually 16:9) before being
Angles: On a DVD-Video disc up to 9 camera angles can be used so
that different views of a scene can be included and the user is able to
switch from one to another while watching the video sequence. An example
is a pop concert, where the viewer can choose which performer to view and
change the view (angle) during the video.
Anti-aliasing: A form of interpolation used when combining images
to provide a smooth transition between pixels. A good example is text over
a plain or textured background. This will require the use of additional
shades of colour and intensity between the foreground text colour and the
AOB: Audio Object, a file on a DVD-Audio disc containing the audio
information. AOBs are equivalent to VOBs used on DVD-Video discs.
AOD: Advanced Optical Disc, a new format being proposed by Toshiba
and NEC as the next generation DVD. AOD discs would use a blue laser to
read them and can hold 15 GB of data per side on a pre-recorded disc, but
20 GB on a re-writable version. The DVD Forum is studying both AOD and Blu-ray
as contenders for a new HD-DVD format.
APRS: Association of Professional Recording Services. The APRS is a
UK organisation that promotes the highest standards of professionalism and
quality within the audio industry. Its members are recording studios,
post-production houses, mastering, replication, pressing and duplicating
facilities, and providers of education and training, as well as audio
engineers, manufacturers, suppliers, and consultants. Its primary aim is
to develop and maintain excellence at all levels within the audio industry
of the United Kingdom. (see www.aprs.co.uk)
APS: Analogue Protection System, Macrovision's copy protection
system for DVD-Video that distorts the video output so that after being
recorded to VHS tape and then played back the video is unwatchable.
Artefact: An unintended, unwanted visual aberration in a video
ASCII: American Standard Code for Information Interchange for
representing text characters. The ASCII character set is the basic set
used by computers for many years.
Aspect Ratio: The relationship of width and height of pixels in an image.
ASV: Audio Still Video, a still image on a DVD-Audio disc. Up to 20
high quality ASVs can be loaded into the player memory before the audio is
played and so can be replaced between tracks where an audio mute is
ATRAC: Adaptive Transform Acoustic Coding, a method to compress
audio data and used in the MiniDisc.
Au: The chemical symbol for Gold, used for the semi-reflective
layer (Layer 0) of dual layer DVD-9 discs.
Authoring System: Software that helps developers design interactive
courseware easily, without the painstaking detail of computer programming.
Autoplay: A feature (eg within Windows 95 or 98) for example
allowing a CD-ROM disc to play automatically when inserted.