A I.1  Glossary of Terms







Absolute Disc Address - see Chapter III, page 1.  The location of a  given 
sector on the disc  (in minutes, seconds and  sectors) contained in    the 
header of each sector in the main channel.

Abstract File  Name  -  see Chapter  III, page  8.   Field of  the    File 
Structure Volume  Descriptor  identifying  the  path  name  of  a     file 
containing a summary of the volume contents; this file can contain   audio 
and video data.

Access Controller   -  see Chapter  VIII,  page 3.   See  Memory    Access 
Controller.

Active Line Scan Period  -  see Chapter V, page 9.  The time taken by  the 
electron beam of a cathode ray tube to move across the visible part of   a 
line on the screen.

Adaptive Delta  Pulse  Code Modulation   -  see Chapter  4,  page  14.   A 
technique  for  converting  analog  audio  into  digital  audio.     Delta 
modulation assumes  close  correlation between  successive  samples.    It 
cannot accurately express large  transients in an audio  signal,   because 
the correlation between successive  samples is too low.   Adaptive   delta 
pulse code modulation  is a  variant of delta  modulation in  which    the 
quantization steps are adapted to the dynamic amplitude variation.    This 
adaptation can  include  a temporary  switch  to PCM.   See  Pulse    Code 
Modulation.

Address of Path Table - see Chapter III,  page 7.  The block address    of 
the first block of the system path table.

ADPCM See Adaptive Delta Pulse Code Modulation.

ADPCM Decoder - see Chapter IV, page 23.  Converts the CD-I audio   sector 
encoded data to 2's Complement 16-bit PCM encoded audio.

Album Identifier   -   see Chapter  III,  page 7.   Field  of  the    File 
Structure Volume Descriptor identifying  the set of discs  (or album)   to 
which the volume belongs.

Album Set Sequence  Number -  see Chapter III,  page 7.   Specifies    the 
relative sequence number of a disc in the album to which it belongs.

AMIN, ASEC, AFRAME  - see  Chapter II, page  7.  An  absolute time   scale 
addressing the whole  of a  Compact Disc and  located in  the subcode    Q 
channel.



Anti-aliasing filter  -  see Chapter  V, page 20.   When a  signal to   be 
sampled contains frequencies higher than half the sampling rate,  aliasing 
will occur.  That is, the reconstituted sampled signal  will not   contain 
these high  frequency  signals, but  will  contain false  low    frequency 
components  instead.   An  anti-aliasing   filter  reduces  aliasing    by 
attenuating these high frequency components before sampling.

Application Identifier  -  see  Chapter III, page 7.   Field of the   File 
Structure Volume  Descriptor  specifying  the  path  name of  the    first 
application program to be executed when the disc is mounted.

Application Specific Coding  Flag -  see Chapter V,  page 94.    Indicates 
whether the video coding  conforms to the specification  of Chapter V   of 
the CD-I Specification or is application specific, i.e. to be  interpreted 
by the application software.

ASCF - see Chapter V, page 94.  See Application Specific Coding Flag.

Asynchronous Execution Service Request  -  see Chapter VII,  page 24.    A 
service request where  the process  will continue to  execute after    the 
request has been made and before the request has been satisfied.

ATIME  - see Chapter II, page 9.  Absolute time on a disc. Expressed   (as 
AMIN, ASEC, AFRAME) in 6-digit BCD in the  Q-channel of the Compact   Disc 
subcode.

Attributes  - see Chapter III, page 21.  Two bytes in a directory   record 
that specify the  permissions and  characteristics of the    corresponding 
file.

Audio Block Field Bytes - see Chapter IV, page 7.  2304 bytes of data   in 
a CD-I audio sector.  An audio block is further subdivided into 18   sound 
groups of 128 bytes each.  The sound groups  have to be encoded in    time 
sequential order.

Audio Channel - see Chapter IV, page 3.  A CD-I track can be divided  into 
several audio channels, one for each audio source.

Audio Channel Selection Register  -  see Appendix II,  page 4. Within   an 
audio sector the channel number can be a  value from 0 to 15.  The   audio 
channel selection  register  selects  audio  channels  and causes    their 
transfer to the audio processor.


Audio Data Representation -  see Chapter IV, page  1.  The way  in   which 
audio data is encoded and stored on a Compact Disc and decoded   according 
to the CD-I specifications.

Audio Decoder Delay - see Chapter VIII, page 10.  The delay caused by  the 
ADPCM decoder and audio processing unit, which should be less than 27  ms. 
This is the delay time between the audio data input to the ADPCM   decoder 
and an audible output.

Audio Functions  -  see Chapter VII, page 47.  Compact Disc File   Manager 
functions which are concerned  with the maintenance and  manipulation   of 
ADPCM sound.

Audio Mixing Control Unit - see Chapter IV,  page 29.  Consists of    four 
attenuators between the two  audio inputs and two  audio outputs of    the 
unit.  The attenuation is controlled by the UCM in steps of 1 dB.

Audio Processing Unit  - see  Chapter IV, page  22.  Converts    digitally 
coded audio information into the left and right  analogue outputs.    Also 
includes an Audio Mixing Control Unit.

Audio Sector - see Chapter IV, page 4.  A sector in which the data   field 
contains audio data.

Audio Sector Data Format - see Chapter IV, page 4.  The data field of   an 
audio sector comprises a  sub-header, an audio data  block of 2304   bytes 
and 20 bytes with value 0.

Audio Sector  Interleaving  - see  Chapter  IV, page  13.   A  method   of 
recording audio sectors with a fixed duty cycle on the disc, according  to 
the average data rate required.

Audio Track - see Chapter II, page 3.   A CD-DA track with digital   audio 
samples encoded as 16-bit wide 2's complement numbers.





Backdrop  - see  Chapter V,  page 91.  The  background image  plane   that 
becomes visible  when  all  or  parts  of  all  other  planes  are    made 
transparent.

Base Case System - see Chapter VIII.  The minimum characteristics   always 
offered by any CD-I system.

Bit Mapped  Text   -  See  Chapter  V,  page  19.   Text  which  is    not 
program-generated in the decoder but which is stored on the disc in  image 
form.

Block Address  - see  Chapter III,  page 1.   A  32-bit integer  that   is 
converted to an absolute disc address to access information on the disc.

Breadth First  Traversal  -   see Chapter  III, page  23.   A method    of 
parsing a tree structure in which each level is completely parsed   before 
moving to each successive level.

Cartesian Coordinate System  -  see Chapter VII, page  65.  A system   for 
locating a point  in a  plane by specifying  its distance  from two   axes 
which intersect at right angles.

Cartoon-style image   - see  Chapter V,  page 19.   An  image   containing 
significant areas of the same color which can  be efficiently run   length 
coded: this is generally true for cartoon images.

CCIR  - see Appendix V, page 1.  Comit_ Consultatif International Radio

CD-DA Controller Decoder - see Chapter VIII, page 3.  The hardware  needed 
to control  the  playing of  a  CD-DA or  CD-I  disc  and to  route    the 
information coming from  the disc,  either in the  form of  CD-DA    audio 
information or other information, for further decoding.

CD-DA Data -  see Chapter  II, page 36.   Data encoded  according to   the 
CD-DA specification.

CD-DA Track  -  see Chapter  I,  page 2.   A  track  on a  Compact    Disc 
containing audio information encoded  according to the CD-Digital    Audio 
specification.

CDFM See Compact Disc File Manager.

CDFM Device Driver  -  see Chapter VII, page  142.  The lowest level    of 
system software which provides the interface between the CDFM and the   CD 
controller.

CD-I Decoder Model - see Chapter II, page  36.  The general structure   of 
the decoding  unit for  decoding CD-I  disc information  containing   four 
independent units.

CD-I Encoder Model - see Chapter II, page 34.  A generalized structure  of 
the encoding process.

CD-I Media Specification - see Chapter I, page 1.  Specifies the  physical 
format of a CD-I  disc, and how various  information types (audio    data, 
video data, and program related data) are coded on a CD-I disc.

CD-I Physical Format - see Chapter II, page  1.  Defines how a CD-I   disc 
is split into the  different types of addressable  physical sectors   (and 
tracks), and  the  general encoding  and  decoding algorithms  of    these 
sectors.

CD-I Physical Sector -  see Chapter III, page  1.  A CD-I  disc   contains 
directly addressable sectors  numbered consecutively  beginning at   zero. 
These are CD-I Physical sectors which contain 2352 bytes representing  the 
synchronization, the header and the data fields.

CD-I Physical Sector Formatter - see Chapter II,  page 34.  A unit   which 
superimposes the CD-I sector format on the incoming data.

CD-I Sector - see Chapter II, page 13.  A unit of data of 2352  sequential 
bytes, directly addressable.

CD-I Sector  Data  -  see  Chapter  II,  page  36.   Sectors    containing 
information encoded in CD-I format.

CD-I Sector  Processor -  see Chapter  II, page  37.   Part of  the   CD-I 
decoder model which decodes the CD-I sectors.

CD-I Standard Character Set  - see Chapter VI,  page 9.  Conforms to   ISO 
8859-1.  The corresponding font  module is always present  in ROM in   the 
Base Case System.

CD-I System - see Chapter I, page 1.  A real-time decoder system   capable 
of playing CD-I discs.

CD-I System Validation  see  Chapter VIII, page 16.   The procedure    for 
checking the correct operation  of a CD-I system  according to the    CD-I 
Full Functional Specification and using a validation disc.

CD-I Track  - see Chapter II, page 14.  A data track containing only  mode 
2 sectors conforming to the CD-I specification.

CD-RTOS  -  see Chapter  VII.  Compact Disc Real  Time Operating   System: 
The name of the operating system used in CD-I players.

CD-RTOS I/O Service  Request  -   see Chapter VII,  page 3.   A    service 
request from  a process  to perform  a device  independent    input/output 
function.

CD-RTOS Kernel  -  see Chapter VII, page 1.  The nucleus of CD-RTOS  which 
is responsible for service request processing, memory management,   system 
initialization, multi-tasking, input/output management and exception   and 
interrupt processing.




CD-RTOS System State  Service Request   -  see Chapter  VII, page  4.    A 
request made to the  CD-RTOS kernel that is  only allowed for    processes 
that are running in system state.

CD-RTOS User State Service Request  -  see Chapter VII, page 1. A  request 
made to the CD-RTOS kernel by a process  that is running in either    user 
state or system state.

Channel Number - see Chapter II, page 22.  A number assigned to pieces  of 
information contained in CD-I sectors to facilitate the selection of  such 
information.

Character Output Functions  -   see Chapter VII, pages  125 to 127.   User 
Communications Manager functions which  are used to display  text on   the 
screen.

Check Polynomial  -  see Chapter  II,  page 26.   A  parameter  used    in 
detecting errors in a string of data.

CIRC - see Chapter II, page 25.  Cross-interleaved  Reed Solomon code,   a 
technique used in error correction.

CLUT -  see Chapter V, page 31.  See Color Look-Up Table.

CLUT Animation - see Chapter V, page 72.  For CLUT coded images, the   256 
values in the CLUT  control the colors of  the entire image.    Therefore, 
some simple animation effects are possible simply by  redefining some   or 
all of the CLUT contents as a function of time.

CLUT (4,7 and 8-bit  and Run-length Coded 3  & 7-bit) -  see Chapter    V, 
pages 48-51.   A series  of standard  representations of  video    signals 
defined for CD-I.

Coded Character Set (File Structure Volume Descriptor) - see Chapter  III, 
page 5.  A method of coding an agreed  alphabet of letters, numbers    and 
other symbols.

Coded Character Set Identifier  - see Chapter III,  page 7. Identifies   a 
character set according to the International Register of Character Sets.







Coding Information - see Chapter II, page 22.   A byte in the    subheader 
that defines the details of the information located  in the data area   of 
the sector.

Color Key - see Chapter V, page 76.   A color look-up table image may   be 
compared on a RGB  basis, pixel-by-pixel to a  true color key,  value   K. 
The value of the  comparison (true or false)  may be used  to effect   the 
image transparency.

Color Look-Up Table  - see Chapter V, page 31. A table containing all  the 
colors which may be used in a particular picture.  Each entry provides  an 
RGB value.   The  picture may  then  be encoded  using  the  table   entry 
addresses rather than the direct RGB values.

Compact Disc File Manager  -  see Chapter VII,  page 23.  A CD-RTOS   file 
manager which handles I/O  requests for the compact  disc drive and    the 
audio decoder.  Provides random  access to disc files  at the byte   level 
through system calls.

Compact Disc Real Time Operating System - see  Chapter VII, page 1.    The 
name of the operating system used in CD-I players.

Compatibility - see Chapter V, page 16.  The property mandatory for   CD-I 
applications, that  they work  correctly on  all CD-I  decoders,  in   the 
following respects: all essential information is presented to  the   user, 
and the user has access to all functions of the application.

Compatible Format - see  Chapter V, page 14.   A coding format  for   CD-I 
images which has equal and opposite minimum aspect  ratio distortion   for 
the '525 line monitor' and '625 line' display formats.

Compression - see Chapter V, page 19  A technique in which the amount   of 
information used to present  a specific image is  reduced by   eliminating 
redundant or unnecessary information.

Computer Graphics   -   see Chapter  V,  page 19.   Pictures  created   by 
computer programs.  Standard drawing functions such as 'line',   'circle', 
etc. are normally used.







Concurrent  (audio)  channel   -   see  Chapter  IV,  page   30.     Block 
multiplexed audio information.  CD-I allows for up to  16 audio   channels 
to be recorded  concurrently on  the disc, so  that by  playing the   disc 
several times and accessing different channels, extended playing time   is 
obtained or  by  playing  the  disc  once, the  same  or  related    audio 
information may  be  obtained  from  parallel  channels, e.g.  the    same 
information in a different language.

Configuration Status Descriptor -  see Chapter VII, page  13.  A list   of 
Device Status Descriptors that describes the hardware configuration of   a 
particular CD-I system.

Control Field (of a Q-channel) - see Chapter  II, page 7.  A 4-bit   field 
immediately following the subcoding "sync patterns" within any   subcoding 
block of the Q-channel.  (See page 41 of the CD-DA specification).

Coordinate Transformation   -  see  Chapter VII,  page 65.   A    software 
mechanism in the User  Communications Manager which provides    resolution 
independence for User Communications Manager functions.  For example,    a 
circle of a specific radius drawn in a drawmap will appear to be the  same 
on the display screen  whether it is drawn  in a normal,  double or   high 
resolution drawmap.

Copyright File Name   -  see  Chapter III, page  7.  Field  of the    File 
Structure Volume Descriptor identifying the path name of  a file used   to 
produce a copyright message when the disc is first mounted.

CRC - see Chapter II, page 26.  See Cyclic Redundancy Check.

Creation Date and Time  - see Chapter III,  page 8.  Field  of the    File 
Structure Volume Descriptor which  contains the date and  time when    the 
CD-I disc was orginally mastered.

Cursor Plane  -  see Chapter V, page 90.   A small graphical image   plane 
that can be moved around the display or  made invisible as required.    It 
can be positioned at any position over the other planes.

Cut - see  Chapter V,  page 65.  A  visual effect  in which  an image   is 
caused to appear suddenly, usually to replace a previous image.


Cyclic Redundancy  Check (CRC)  - see  Chapter II,  page  26.  An    error 
detection code scheme for the CD-I sectors data  field.Data Integrity    - 
see Chapter II, page 25.  The preservation, against  loss or   corruption, 
of programs or data for their intended purposes.

Data Preparer Identifier  -  see Chapter III, page 7.  Field of the   File 
Structure Volume  Descriptor  identifying  the  person  or other    entity 
responsible for the preparation of data recorded on the volume.

Data Retrieval Structure   -  see Chapter III.  The  organisation of   the 
storing of and searching for large quantities of data and making  selected 
data available.

Data Symbol -  see Chapter  II, page 2.   An entity  made up  of n    bits 
representing a value between 0 and 2n-1.

Data Track - see Chapter II, page 3.   A CD-I track with data encoded   as 
8-bit wide symbols (bytes) organized in sectors.

DCP - see Chapter VII, page 59.  See Display Control Program.

Decoder model  - see Chapter V, page 34.   Representation of a method   of 
translating or determining (decoding) encoded information.

Delta YUV   -   see Chapter  V,  page 20.   "YUV"  is  a picture    coding 
technique in  which  each pixel  is  represented by  a  measure  of    its 
luminance (brightness: Y) and  chrominance (color: U and  V)   components. 
Delta YUV is a  compression technique in which  the differences    between 
successive Y,  U  and V  values  are encoded  rather  than  the   absolute 
quantities.

Derived Resolutions   -   see  Chapter  V,  page  6.   Double  and    high 
resolution.

Device Descriptor   -   see Appendix  VII.2,  page 27.    A  data   module 
consisting of  a  table  of  initial  values of  the  parameters  for    a 
particular hardware device.

Device Status Descriptor - see Chapter VII, page  13.  A descriptor   that 
lists the  capabilities  of a  device.   The possible  capabilities    are 
specified, per device type, in Appendix VII.2.

Digital Input Interface  see Appendix VIII, page 8.  A symmetrical  subset 
of the  Digital  Output  described  in  the  attachment  to  the     CD-DA 
specification.


Directly Addressable Sector - see Chapter III, page 1.  A sector that  may 
be accessed directly (as opposed to sequentially) through its address   in 
terms of time and number of sectors.

Directory Files - see  Chapter III, page 18.   Files used extensively   by 
the Compact Disc file management system to locate  other files on a   CD-I 
disc.

Directory Record - see  Chapter III, page 18.   A record describing    one 
file in a directory.

Directory Search Method - see Chapter III, page  23.  The method used   to 
locate a specific file on the disc.  This  method allows any file to    be 
opened using only one seek.

Directory Structure - see Chapter III, page 18.  The organization of  file 
descriptor records within a directory.

Disc Directory  - see Chapter III, page 17.   Directory structure of   the 
CD-I disc  starting  with a  Root  directory and  containing  names    and 
characteristics of files and subdirectories of the disc.

Disc Label  see Chapter III, page 2.  The information in the first   track 
of a CD-I disc  concerning the disc type  and format, the  status of   the 
disc as a  single entity  or part of  an album,  the data  size and    the 
position of the file directory and boot modules.

Disc Label Record Type  - see Chapter III,  page 5.  A  byte in the   File 
Structure Volume Descriptor Record  that specifies whether the    standard 
character set or an alternate character set is  used for the text   fields 
in the File Structure Volume Descriptor, directory records and path  table 
entries.

Disc Logical Format - see Chapter III, page 1.  Specifies the contents  of 
CD-I sectors.

Display Controller  - see  Chapter VIII, page 3.   Two-path device   which 
takes pixel data from the two banks of RAM of a CD-I player and   combines 
them to produce a single analog RGB video output.







Display Control Program  -  see Chapter VII, page  59.  A set of   command 
codes which are interpreted  by the display hardware  during either    the 
horizontal or vertical retrace periods.  The codes can be used to  perform 
a variety  of functions:  definition of  background colors,  entries   for 
color look-up tables, display parameters, etc.

Display Line Start Pointers - see Chapter V, page 57.  Indicates where  in 
memory the display shall start on a line-by-line  basis. If there is    no 
display line start  point for  a given line,  the line  will start  at   a 
memory address directly after the end of the previous line.

Dissolve - see Chapter V, page 80.  The simultaneous fade-in of one  image 
and fade-out of another.

Double Resolution  -  see Chapter V, page 6.  A double resolution  picture 
has twice as many pixels as a normal resolution picture in the  horizontal 
direction, but the same number in the vertical direction.

Double written  - see Chapter II, page 21.   A method of improving    data 
integrity whereby the data  is written twice with  a 4-byte    separation. 
Achieves data integrity levels equivalent to Mode 1 EDC/ECC.

Drawmap  -  see Chapter VII, page 58.  A block of memory allocated by  the 
User Communications Manager to store image data.

DSD - see Device Status Descriptor.

DYUV  - see Chapter V, page 20.  See Delta YUV.

Dynamic CLUT  Update -  see Chapter  V, page  73.   CLUT entries  can   be 
reassigned with new RGB values via the display control program during  the 
line or  field  retrace period.   This  technique allows  the  number   of 
available colors to be extended beyond the respective maximum numbers   of 
8, 16, 128  and 256  for CLUT  3, CLUT  4,  CLUT 7  and CLUT  8    encoded 
pictures.

ECC Codeword - see  Chapter II, page 27.   Part of the  error   correction 
code field.

ECC Field  see Error Correction Code field.

EDC Codeword  - see  Chapter II,  page 26.   A  unit of  information    or 
codeword used in the error detection process.

Error Detection  Code  Field -  see  Chapter II,  page  26.   The    field 
containing error detection code information.

EDC Field - see Chapter II, page 26.  See Error Detection Code field.

EDC Parity - see Chapter II, page 26.   Part of the information used    in 
the error detection process.

Effective Date and Time - see Chapter III,  page 8.  If the data on    the 
disc are  not valid  before a  specific time,  this  field of  the    File 
Structure Volume Descriptor indicates the time at which  the data   become 
useful.

Emphasis - see  Chapter IV,  page 16.  Increasing  the level  of    higher 
signal frequencies relative to the lower frequencies prior  to   recording 
or broadcasting.  Used to improve signal-to-noise ratio.

Empty Sector - see Chapter II, page 33.   A Form 1 or Form 2 sector     in 
which the data field consists of 2324 bytes which are all set to 0.

Encoding model  - see Chapter V, page 20.  Representation of a method   of 
translating (encoding) from one method of expression to another.

End-of-File bit - see Chapter II, page 23.  A bit in the submode byte   of 
the subheader that is set to 1 in the last sector of a file.










End-of-Record bit - see Chapter II, page 24.   A bit in the submode   byte 
of the subheader that is set to 1 for the last sector of a real time    or 
non-real time record.

EOF-bit - see Chapter II, page 23.  see End-Of-File bit

EOR-bit - see Chapter II, page 24.  See End-Of-Record bit

Error Concealment - see Chapter V, page 62.  A variety of techniques  used 
for concealing errors in visual images displayed from a CD-I disc.

Error Correction  Code  Field -  see  Chapter II,  page  27.   The   field 
containing error correction code information.

Error Flag - see  Chapter II, page 38.   Part of the  data field in    the 
error detection  process  which  indicates  whether  an error  has    been 
detected in the given sector.

Even/Odd Lines Flag - see Chapter VII, page  78.  When error   concealment 
is used, this flag indicates whether the sector contains the even or   odd 
lines of the image.

Executable Object Code  - see  Chapter VI, page  2.  The  output from    a 
compiler, an assembler, a  linkage editor or a  linker, which is  in   the 
machine code for a particular processor, with each loadable program  being 
one named file (module).

Expiration Date and Time - see Chapter III,  page 8.  If the data on   the 
disc are valid only for a limited time, this field of the File   Structure 
Volume Descriptor indicates the time at which the data become obsolete.

Extended Attribute Record - See Chapter III, page  19.  A number of   data 
blocks at  the  beginning of  a  file reserved  for  extended    attribute 
information.

Fade - see Chapter V, page 80.  A gradual decrease (fade-out) or  increase 
(fade-in) in the brightness level of an image.

Field Control Table - see Chapter V, page 54.  A one-dimensional array  of 
Display Control instructions which  are carried out before  the start   of 
each field.

File - see  Chapter III,  page 26.  A  collection of  logically    related 
records identifiable in a directory

File Descriptor Record - see Chapter III, page 18.  Used to store   common 
format and attribute information needed to access a file on a disc.

File Flags  - see  Chapter III, page 20.   Field of the  File   Descriptor 
Record containing  information concerning  the status  of a  file,    e.g. 
hidden.

File Manager   -   see Chapter  VII,  page 19.   A  CD-RTOS  module   that 
processes raw data streams for use by a class of similar devices.

File Number -  see Chapter  II, page 22.   Identifies all  sectors    that 
belong to one and the same file.

File Pointer  - see Chapter VII, page 30.   The location in a file   where 
the next operation is to be performed.

File Structure Standard Version Number - see Chapter III, page 8.  Defines 
the revision number of  the file structure standard  which the disc   file 
structure obeys.

File Structure Volume Descriptor  -  see Chapter III,  page 3. Record   of 
the Disc Label describing  all necessary items related  to the files    or 
parts of the files recorded on the volume.

Filter and Range  Selector -  see Chapter IV,  page 16.   Generates    the 
values called filter (F) and range (R) depending  on the peak values    of 
the predictor units.

First Order & Second Order Digital Filters  -  see Chapter IV, page    14. 
Filters employing digital techniques,  based on equations involving    the 
first or second derivative respectively.

Font Module -  see Chapter  VII, page 69.   A CD-RTOS  data module    that 
contains the bitmap images for each displayable character.



Form - see  Chapter II,  page 23.  Information  on a  CD-I track  may   be 
recorded in either Form  1 or Form 2  format, depending on  the level   of 
data integrity required.

Form bit  see  Chapter II,  page 23.  Bit  in the  submode byte  of    the 
subheader field defining the data form (Form 1 or Form 2) for the sector.

Form Value Detector - see Chapter II, page 35.  A unit which detects   the 
value of the form bit.

Frame - see Chapter II, page 10.  The frame is the basic entity for   data 
addressing in CD-DA: a CD player reads 75 frames per second.

Frame Number - see Chapter II, page 10.  Identification, for   explanation 
purposes, of the successive frames.

Gain Control  see Chapter IV, page 14.  Multiplication  of the data by   a 
gain factor.

Getstat  -  see Chapter  VII, page 25.  An  I/O service request  that   is 
used to retrieve information about a specific device; typically a  getstat 
function call will not be device independent.

GF - see Chapter II, page 27.  See Goloia Field.

Goloia Field  - see Chapter II, page 27.   A finite field concept used  in 
error correction coding.

Glyph  - see Chapter VII, page 68.  The  bitmap image for a symbol.    For 
example, the bitmap image of the letter "a"  is the glyph for the   letter 
"a".

Glyph Data Table  - see Chapter VII, page  71.  A table in a font   module 
which contains information about each glyph in the font module.

Granulation - see Chapter V, page 88.  An  effect whereby the   resolution 
of an image  changes without  its size altering.   It is  produced by    a 
combination of pixel hold and line hold functions.

Graphics Cursor Functions   -  see  Chapter VII, pages  87 to  90.    User 
Communications Manager functions which control the shape, size, color  and 
position of the graphics cursor on the display screen.

Graphics Drawing Functions  -   see Chapter VII, pages  101 to 111.   User 
Communications Manager  functions  which  are  used  to draw  images    in 
drawmaps.

Group Execute (File attribute bit)  - see Chapter III, page 21. This   bit 
of the attribute field  of a directory record  specifies that only   users 
belonging to an identified  group can execute the  program contained    in 
this file.

Group Read (File attribute bit)  - see Chaptr  II, page 21.  This bit   of 
the attribute  field of  a directory  record specifies  that  only   users 
belonging to an identified group can access this file.


Grouping Factor - see Chapter V, page 97.   To support error   concealment 
by line repeat, the video data elements of  the even and odd lines of   an 
image are separated from  each other and the  two resultant data   streams 
interleaved on  disc.  The  interleaving breaks  each data  stream    into 
groups of  a constant  number of  sectors.  This  number  is called    the 
'grouping factor'.  Hardware  Configuration  Status  Descriptor   -    see 
Chapter VII, page 13.  See Configuration Status Descriptor.

Header Field - see Chapter II, page 20.  A four-byte field, within a  CD-I 
sector which contains the CD-I sector address and the mode information.

High Resolution  -  see Chapter V, page 6.  A high resolution picture  has 
twice as  many  pixels  as  a  normal resolution  picture  in  both    the 
horizontal and vertical directions.

Image Coding Method - see Chapter V, page 19.  One of a number of ways  of 
coding the  RGB  pixel values  of  an image,  usually  with  the aim    of 
compressing the  amount  of data  needed  to represent  the  image.    The 
specified methods are RGB555, DYUV, QHY, CLUT and Runlength CLUT.

Image Contribution Factor - see Chapter V, page 79.  See 'Image Mixing'.

Image Line Pointer Table - see Chapter V, page 57.  Each line of an  image 
as stored in image memory may start at  an arbitrary address within    the 
available image  memory.   An image  line  pointer table  of  line   start 
addresses may be maintained for each image.

Image Mixing - see Chapter V, page 79.   The images of two    superimposed 
planes, A and  B, may  be intermixed after  decoding to  RGB on  a   pixel 
basis.  The resultant image is equal to the  sum of the two images,   each 
multiplied by its own Image Contribution Factor.

Image Plane  -  see Chapter V, page 40.  A displayed image may be   formed 
by the superimposition of a number of component  pictures. Each of   these 
constitutes an image plane.

Index  see Chapter II,  page 9.  Subdivision of  a track in  the   program 
area only.  Expressed in 2-digit BCD in the Q-channel of the Compact  Disc 
subcode.

Information Area - see Chapter II, page 9.  Synonymous to recorded   area. 
Contains the lead-in area, program area and lead-out area.

Information Track - see Chapter II, page 3.   One of the up to 99   tracks 
on a  Compact Disc  containing encoded  information.  Each  track  has   a 
minimum length of 4 seconds and can either be a data or an audio track.

Information Types - see  Chapter I, page 1.   Three types of   information 
are identified in CD-I namely audio data, video data and program   related 
data.

Init Module  -   see Chapter  VII, page 11.   The system    initialization 
module that contains the parameters to be used in starting up the system.

Interlace  -  see  Chapter  V,  page  39.  In  television  and    computer 
graphics, a system of  scanning a picture using  two fields.  The    first 
line-by-line scan   (field)  sweeps  alternate  line  positions  on    the 
picture, the second sweeps  the gaps between the  first, completing    the 
total structure of the picture.   Interlace scanning reduces the   flicker 
inherent with low refresh rates.

Interleaved Files - see Chapter III, page 29.  Interleaved blocks of  data 
from one file  with blocks  from other files  on the  CD-I disc.     Files 
having their sectors physically interleaved on disc.

Interleaving (sectors)  -   see Chapter  III, page 29.   The process    of 
physically separating the sectors  within one logical file  so that    the 
data can be  retrieved at  the rate required  for processing.  The   audio 
blocks in a real-time  file must arrive from  a CD-I disc  at the    audio 
processor at  a  very precise  rate.  Sectors between  successive    audio 
sectors can be used in a variety of ways: video or text data sectors   can 
be placed within these gaps.

International Reference Version ISO 646 Character Set  - see Chapter  III, 
page 5.   Identifies the  character set  described in  the   International 
Standard ISO 646 as International Reference Version.

Interpolation -  see Chapter  V, page  43.  The  process  of filling    in 
intermediate values of a  series between known values  of the series,   by 
computation from the known values.

Interpolation Scheme - see Chapter II, page 25.   A method of   concealing 
errors.

Irregular Updates - see  Chapter V, page 70.   One of the  two types    of 
partial updates available within  CD-I, where the area  to be updated   is 
irregular in shape.

ISO 646 -  see Chapter  III, page 5.   The international  standard for   a 
7-bit coded character

ISO 2022  - see Chapter III, page 5.   International Standard   specifying 
the methods (through shift function or escape sequences) to extend 7 or  8 
bit coded character sets.


ISO 2375  -  see Chapter III, page 6.  International Standard   specifying 
the registration procedure of escape sequences used for code extension  of 
a character set.  It refers particularly to the  "International   Register 
of coded character sets to be used with escape sequences".

ISO 8859-1  - see  Chapter VI, page 9.   The specification of  the   8-bit 
coded character set for the Latin Alphabet Number  1, used for the    CD-I 
standard character set definition.

Kernel  -  see Chapter  VII, page 1.  The  heart of an  operating   system 
that is responsible for most system-related functions.

Keyboard  Input  Functions   -   see  Chapter  VII,  pages   133.     User 
Communications manager functions  which are  used to get  character   data 
from a keyboard device.

LBN - see Chapter III, page 19.  See Logical Block Number.

Lead-in area  see Chapter II, page 4.  A  track (number 0) preceding   the 
program area of a Compact Disc.

Lead-in Q-channel Frame - see Chapter II, page 7.  A frame of  information 
contained in the Q-subchannel, in the lead-in area of a Compact Disc:  the 
Table of Contents of the CD-DA tracks is contained in such frames.

Lead-out area  see Chapter  II, page 6.  A  track (number $AA)   following 
the program area of a Compact Disc.
           
Line Control Table - see Chapter V, page 54.  A two-dimensional array   of 
Display Control instructions,  each row  of which is  associated with    a 
displayed line.

Line Hold,  Line Repeat   - see  Chapter V,  page  87.  In  the   vertical 
direction, mosaic  effects are  produced by  repeating lines  using    the 
display line start pointers in the DCP.

Line Pointer Table  - see  Chapter V, page  57.  See  Image Line   Pointer 
Table.

Linear Interpolation  - see Chapter V, pages 29 and 43. Interpolation   in 
which an intermediate  value between  two known values  is taken  as   the 
average of these two values.  Used in the process of encoding QHY data  to 
obtain high resolution images  from normal resolution images  and in   the 
decoding of the U and V components of a DYUV image.

Loadable Program -  see Chapter  VI, page 2.   A named  file    containing 
object code information used in CD-I.

Logical Block Number (LBN) - see Chapter III, page 19.  The block  address 
of an element of the disc file structure.

Logical Block Size -  see Chapter III, page  7.  Defines the  size of    a 
block in bytes as seen by the file system.  For CD-I this is always   2048 
bytes.

Logical Command Level  see Appendix VIII, page 1.   The level   describing 
the logical part of a command (that is the effect a command may have)   as 
opposed to its  physical format  in terms of  allocation and    electrical 
wires and levels.

Magnification -  see Chapter  V, page  88.  The  pixel  and line    repeat 
functions may be used to produce an image magnification effect, e.g.   for 
examining details of a structure of the image.

Main Channel  Address -  see Chapter  III, page  1.   See Absolute    Disc 
Address.

Matte - see Chapter V, page 81.  Any  connected area of the display.    It 
is used to control the transparency of image planes.

Memory Access  Controller  -  see  Chapter  VII, page  57.   A    hardware 
component that retrieves  pixel data  from memory and  passes it  to   the 
video real-time decoder for display.  The access to memory is shared  with 
the processor.

Memory Module - see Chapter VII, page 19.   A named block of    executable 
program statements or data that can be loaded by CD-RTOS into memory.

Message Sectors  see Chapter  II, page 33.  CD-I  sectors containing    an 
audio message encoded as CD-DA audio data.  This message asks the user  to 
lower the volume,  if a  CD-I track is  being played  on a  simple   CD-DA 
player.

Mode 2 See Chapter II, page 4.  One  of the two physical sector    formats 
defined for  CD-ROM.  CD-I  sector specification  further describes    two 
types of "Mode 2" sectors according to their "submode" contents:
Form 1 sectors incorporate EDC/ECC error detection and correction fields.
Form 2 sectors incorporate  an auxiliary data field  instead of    EDC/ECC 
error detection and correction fields.

Mode byte  - see Chapter II, page 20.   Byte in the sector header    field 
defining the data mode.  Always Mode 2 for CD-I tracks.

Mode Detector - see Chapter II, page 38.  Part of one of the units in  the 
CD-I decoder model which detects the mode value of a data sector.

Modification Date and Time - see Chapter III, page 8.  The date and   time 
field in the File  Structure Volume Descriptor indicating  when the   disc 
was last changed, e.g. re-mastered.





Mosaic Pixel Repeat Factor - see Chapter VIII, page 12.  Factor by   which 
the resolution of an  image is reduced through  the mosaic effects    (see 
V.5.11).  Its  value is  restricted to 2, 4,  8 or 16  in the Base    Case 
system.

Mosaics - see Chapter  V, page 85.  A  group of visual  effect   functions 
which have the effect of reducing an image's resolution, by repeating   or 
holding pixel values.  See Pixel Hold and Pixel Repeat.

Mouse   - see Appendix VII.2, page 17.  A palm sized unit equipped   with, 
typically, two  control  buttons,  used  as  an X-Y  pointer  device    to 
manipulate a screen  display and  invoke and control  utility   functions. 
Functions are  invoked  by moving  the  mouse to  designated  areas    and 
pressing one of the buttons.

MPU  - see Chapter VI, page 1.  Micro processing unit.

Natural Images   - See  Chapter V,  pages 19,  20.   Pictures which    are 
photographic in nature and appear realistic.

Near-instantaneous Compression  - see  Chapter IV, page 14.    Compression 
performed quickly enough to have no perceptible effect  on the timing   of 
the presentation of the information concerned.

Noise Shaper Unit - see Chapter IV, page  16.  Compensates for the   extra 
noise introduced in the predictor unit.

Non-Volatile Memory  -   see Chapter  VIII, page 17.   A memory  able   to 
retain its contents when the main power to the unit is removed.

Non-Volatile RAM File Manager   -  see Chapter VII,  page 19.  The    file 
manager that is used to maintain the contents of the non-volatile RAM   in 
the CD-I system.

Normal Resolution  -  see Chapter V, page 5.   A displayed image may    be 
regarded as a rectangular array of pixels.  The resolution refers to   the 
number of pixels in  the horizontal and vertical  directions.  A    normal 
resolution picture is a picture with the lowest resolution defined in  the 
CD-I system  and  reflects  the  resolution  of  present  525/625    color 
television sets.

NRF - see Chapter VII, page 167.  See Non-Volatile RAM File Manager.

Number of Volumes in Album - see Chapter  III, page 7.  Total number    of 
discs in the album to which a disc belongs.

NVRAM  - see Chapter VIII, page 17.  See Non-Volatile Memory

Object Code - see Chapter VI, page 2.  The code of a user's program  after 
it has been  translated by  means of an  assembler or  a compiler  and   a 
linker.

Odd/Even Line  Separation  -  see  Chapter  V,  page  62.   When     error 
concealment is to be used, the even and  odd lines of an image are   coded 
on  a  disc  in  separate  sectors  and  are   physically  separated    by 
interleaving so  as  to minimize  the  chance of  an  error  occuring   on 
adjacent lines.

One dimensional Run-length Coding  -  see Chapter V, page 19.  A   picture 
coding technique  in which  pixel data  is compressed  using    run-length 
coding in the horizontal direction only.

Overlay - see Chapter  V, page 75.  The  process of superimposing    image 
planes in a given visual image.

Overscan  - see Chapter V, page 5.  The  extension of the deflection    of 
the electron beam of a Cathode Ray Tube (CRT) beyond the usable   physical 
dimensions of the screen.  In this way an image always fills the   visible 
part of the display screen, but some of the image is lost at the edges.

Owner Execute (File attribute bit)  -  see Chapter III, page 21. This  bit 
of the attribute field of a directory record,  if set to one,    specifies 
that only the user  identified  as "owner" of  the file can  execute   the 
program contained in this file.

Owner I.D. - see Chapter III, page 21.  Contains the user   identification 
number of the creator of a file.


Panning  see Chapter  IV, page  29.  The distribution  of a  mono   signal 
between left and right audio channels.

Parent Directory  - see Chapter III, page 23.  A directory which  contains 
sub-directories.

Partial Update  -  see  Chapter V, page 11.   New image data  written   to 
part of an image which has already been loaded into a drawmap.

Path Descriptor  - see Chapter VII, page 143.   A data structure used   to 
represent an  open  file; each  open  file is  associated  with  a    path 
descriptor.

Path Table, Path Table Index - see Chapter  III, page 23.  The table    or 
index  used  for  directory  search.   Describes  the  entire    directory 
structure on a disc.  Permits any file on  disc to be opened using    only 
one seek.

Path Table Entry - see Chapter III, page  23.  Individual element of   the 
Path Table which is used to locate each  directory or sub directory on   a 
disc.

Path Table Size - see Chapter III, page 7.  A field in the File  Structure 
Volume Descriptor which  defines the  size in bytes  of the  system   path 
table.

PCM  - See Chapter IV, page 23.  See Pulse Code Modulation.

Physically Interleave Files - see Chapter III, page 29. Interleave  blocks 
of data of one file with blocks from  other files on the CD-I disc;    for 
example the interleaving of audio blocks in a  real-time file with   other 
data blocks.

Pipeman - see Appendix VII.1, Chapter 10.  The Pipe File Manager, one   of 
the file managers  of CD-RTOS  that supports interprocess    communication 
through the use of "pipes".

Pixel  - see Chapter V, page 5.  An image may be considered to be made  up 
of a number of small units known as pixels or picture elements.  A   pixel 
is the  smallest  element  of  an  image which  can  be  manipulated    or 
identified.

Pixel Aspect Ratio - see Chapter V, page 14.  The ratio of the height   of 
a pixel to its width.

Pixel Data  Formats   -   see Chapter  V, pages  100  to 105.   The   disc 
formats of all the defined coding methods for pixel data.
Pixel Hold - see Chapter V, page 86.  Method used to reduce resolution  by 
holding the RGB  value of  every nth pixel  for n  pixel periods.     This 
function operates after the pixel codes have been decoded to RGB.

Pixel Pairs  - see Chapter V, page 6.   In 3-bit run-length coded   images 
and 4-bit CLUT encoded pictures, two pixels are  put together to make   up 
one byte, and are then regarded for most purposes (e.g. the length of  the 
run in run-length coded pictures) as a single pixel pair.

Pixel Repeat  - see Chapter V, page 87.   A visual effect function    that 
repeats pixel  values  from  an  image  memory  to  produce     horizontal 
magnification.  Used in RGB 555 and CLUT image decoding only.
           
Plane  See Image Plane.

Play Control Block -  see Chapter VII, page  38.  A data  structure   that 
contains the necessary information concerning the data to be accessed   on 
the disc for the current or next Real-Time  Record Play function of    the 
Compact Disc File Manager.

Play Control List -  see Chapter VII, page  40.  A structured  list   that 
controls the destination of the data.

Player's Default Character  Set  -   see Chapter III,  page 3.   Set    of 
characters tentatively  selected  by the  CD-I  player when  a  disc    is 
initially accessed.  May be  different from the CD-I  standard   character 
set (for instance Shifted JIS Kanji for a Japanese player).

POINT, PMIN, PSEC, PFRAME - see Chapter II,  page 7.  During the   lead-in 
track of a CD-I disc a Table of Contents is present with-in the subcode  Q 
channel (see p.43 of the CD-DA specification): PMIN, PSEC and PFRAME  give 
the starting point (on the absolute time scale ATIME) of the CD-DA   track 
number, pointed to by POINT.

Pointer  Input  Functions    -   see   Chapter  VII,  page   131.     User 
Communications Manager  functions  which  are  used  to  get    coordinate 
information from a pointing device.

Polygon  - see Chapter VII, page 106.  A closed figure that is bounded  by 
straight lines.

Polyline  - see  Chapter VII,  page 103.  A  sequence of  lines that   are 
connected end to end  sequentially but do not  necessarily form a   closed 
figure.
Predictor Selector Unit - see Chapter IV, page 16.  Sends the data  chosen 
by the predictor unit to the gain control unit.

Predictor Unit (filters)  -  see Chapter IV, page 16.  A device  (filters) 
used in ADPCM encoding to achieve effective response  to   audio-frequency 
distribution fluctuations.

Primitive Polynomial - see Chapter II, page 27.  A polynomial   generating 
a field in the error correction code process.

Privileged Instructions  -  see  Chapter VI, page 7.   Instructions   that 
can only be executed by the processor in the "system state".

Process Scheduling  - see Chapter VII, page 1.  A method of allowing  each 
of a  series  of  processes  to  obtain  some  execution  time  on     the 
microprocessing unit, allowing each process to eventually finish.

Program Area   see Chapter  II, page  5.  The  area  of a  Compact    Disc 
containing the program and consisting of a maximum  of 99 audio or    data 
tracks.

Program Related Data  - see Chapter VI.  Data to be read and processed  by 
the CD-I application.

Program-Related  Data  Representations   -   see  Chapter  VI,  page    1. 
Conventions applicable to  data to  be read and  processed by  the    CD-I 
application.

Publisher Identifier  -   see Chapter  III, page 7.   Field of  the   File 
Structure Volume Descriptor identifying the person or entity   responsible 
for the definition of the volume contents.

Pulse Code  Modulation  - see  Chapter  IV, page  23.   A  technique   for 
recording analog  information in  digital form.   The analog  signal    is 
sampled and the sampled value is quantized, i.e.  represented by a   fixed 
length binary number.  This number is then transmitted as a  corresponding 
set of pulses.

P-Words - see Chapter II, page 28.  Column codewords in the parity   check 
matrix.

Q-Words - see Chapter II, page 28.  Row codewords contained in the  parity 
check matrix.

QHY  - see Chapter V, page 26.  See Quantized High Y.

QHY Quantization Levels  -  see Chapter V, page  29.  The QHY   difference 
values, which need to  be added to the  normal resolution quantities    to 
generate a pseudo-high  resolution image,  are 8-bit quantities    varying 
between 0 and  255.  Eight  values are chosen  from these  256    possible 
quantities.  Each difference value is then made equal  to the nearest   of 
these eight, and a three bit number is  used to represent it.  The   eight 
chosen values are known as quantization levels.

Quantized High Y  -  see Chapter V, page 26.  A coding technique used   to 
reduce the quantity of  data required to encode  a high resolution    type 
picture: a normal resolution  DYUV image is recorded  together with    the 
data which needs  to be  added to it  to turn  the luminance  (Y) of   the 
picture to the equivalent  of high resolution.  The  latter data   further 
compressed is termed 'QHY'.

Quantizer  - see Chapter V, page 29.  A  device or circuit which   assigns 
fixed binary  values  to  sampled  analog  signals in    analog-to-digital 
conversion.


RAM  - see Chapter VIII, page 5.  Random Access Memory.  In computing  (1) 
a memory chip used  with microprocessors. Information can  be both    read 
from, and written  into the  memory but the  contents are  lost when   the 
power supply is removed, (2) any form of storage in which the access  time 
for any item of  data is independent of  the location of  the data    most 
recently obtained,  e.g.  immediate access  store  has a  random    access 
capability but magnetic disk does not.

Raw Sector  - see  Chapter VII, page 36.   A sector of  information   that 
includes not only the data field but also the header, subheader and  error 
detection and correction information, if any.

Read Only Memory -  see Chapter VII, page  11.  In computing,  a   storage 
device whose  contents can  only be  changed by  a  particular user,    by 
particular operating  conditions or  by a  particular external    process. 
Read only storage can include storage media where  the writing action   is 
inhibited by the Operating  System or by some  mechanical device, e.g.   a 
tag on a diskette.  The term ROM implies a storage device not designed  to 
be modified by conventional write procedures and which  is used to   store 
permanent information in computers and microcomputers, e.g. the  Operating 
System  and   BASIC  interpreters   are  often   supplied  in   ROM     on 
microcomputers.

Real-Time Behaviour - see Chapter II, page 25.  The behaviour of a  system 
able to follow real time constraints (such as  the rotational speed of   a 
CD-I disc).

Real-Time Decoder  - see Chapter V, page 35.   A hardware component   that 
is capable of converting data from one format to another in real time.

Real-Time File - see Chapter III, page 28.   A file containing at    least 
one real-time record.

Real-Time Record - see Chapter III, page 28.  A logical record in a   CD-I 
file containing audio, video, and/or computer data that must be  retrieved 
from a CD-I disc at a precise rate.

Real-Time Sector  -  see Chapter  II,  page 23.   Data  that  has to    be 
processed without  interrupting  the  real-time  behaviour  of the    CD-I 
system.

Record  - see Chapter III, page 18.  The logical component of a file.


Recorded Area - see Chapter II, page 3.  The total area of a Compact  Disc 
including the lead-in area, the program area and the lead-out area.

Rectangular Updates - see Chapter V, page 69.   One of the two types    of 
partial updates available within CD-I, where the area to be updated is  in 
rectangular form.

Reduced Resolution - see  Chapter V, page 89.   The magnification   effect 
produced by pixel and line repeat may be used to produce a low  resolution 
image allowing fast update from the disc of a larger than normal  animated 
screen area.   This  is an  alternative  to animation,  like    run-length 
compression, which may be chosen for specific applications.

Reed Solomon Codewords - see Chapter II, page 28.  Codewords used in   the 
Reed Solomon encoding and decoding process.

RGB  - see Chapter V, page 19.  Every color can be represented as the  sum 
of different proportions of the three primary colors, red (R), green   (G) 
and blue (B).  In RGB encoding, every pixel  is represented by its R,    G 
and B components.  These  are values which, on  presentation to   suitable 
digital to analogue converters will give the correct voltages required  by 
the red, green and blue guns of a  cathode ray tube to produce the   color 
of the pixel on the display screen.

RGB 555  -  see Chapter V, page 48.  A method of coding visual images   as 
5 bits per red, green and blue component.  See also RGB.

Region  - see Chapter  VII, page 65.  A  software mechanism in  the   User 
Communications Manager which is used to limit the  area of drawing in    a 
drawmap and to set up mattes.

Reserved Field (within Form 2 sectors) - see Chapter II, page 32. A  field 
reserved for quality control during the CD-I disc production process.

Revision Number  -  see  Chapter VII, page 13.   A field in  the   CD-RTOS 
module header that specifies which version of a module this is.

ROM See Read Only Memory.

Root Directory - see Chapter III, page 17.   The highest level   directory 
contained on a disc.  A root directory must reside on every CD-I disc.
Rotational Latency - see Chapter III, page 29.   The time taken for    the 
disc to rotate under  the read head until  the required sector  or   frame 
becomes available for reading.


Run-length Coding  -  see Chapter V, page 49.  A picture data  compression 
technique which uses two-byte codes.  The first byte identifies color  and 
the second byte tells the decoder how many  consecutive pixels are to   be 
of this color.


Safety Area  -  see Chapter V, page 7.  That part of an image   (expressed 
in terms  of pixels)  that is  guaranteed to  be  displayed despite    all 
tolerance values that can occur in monitors and TV sets.

Sample Rate Converter  - see Chapter IV, page 1.  Unit which converts  PCM 
encoded audio signal into a new PCM encoded audio signal with a  different 
sampling frequency.

Scheduling Algorithm  -  see Chapter VII, page 24.  The algorithm used  by 
the kernel to determine  which process is to  be scheduled for   execution 
next.

Scrambling  - see Chapter  II, page 18.  A  technique used in  CD-I.   All 
data, except for the data in the synchronization field, is scrambled:  the 
contents of a 15-bit shift register scrambler is EXOR-ed with the   serial 
information bit by bit.

Scramble Register -  see Chapter  II, page 18.   A register  used in   the 
scrambling and descrambling process for all data in a CD-I sector  (except 
the synchronization field).

Scroll -  see  Chapter V,  page  66.  The  repeated  repositioning  of   a 
displayed image within a large image.  Motion may be vertical,  horizontal 
or a combination of the two.

Sector - see Chapter III, page 1.  Reserved abbreviation used for a   CD-I 
physical sector.

Sector Address -  see Chapter  II, page 20.   The physical  address of   a 
sector expressed in minutes, seconds and sector number. Contained in   the 
address part of the sector header.

Sector Format  Multiplexer -  see Chapter  II, page  35.   A unit    which 
multiplexes the various sector information.

Sector Interleaver - see Chapter II, page 35.   A unit which   interleaves 
the sectors with various information types together.

Sector Structure - see Chapter II, page 25.  The method of encoding   data 
within a sector.

Seek  -  see Chapter VII, page 23.  The action of changing, within a  CD-I 
file, the location of the current file pointer.   It also causes the    CD 
drive reading head to move to the required location.


Service Request  -   see Chapter  VII, page 3.   A request  made to    the 
kernel by an application to perform a specific activity.

Setstat  - see Chapter VII, page 30.  An I/O service request that is  used 
to make a request or to change the status of a specific device;  typically 
a setstat function call will not be device independent.

Shifted JIS  Kanji  -  see Chapter  VI, page  11.   A Japanese    standard 
defining a coded Kanji character set.

Sleep  - see Chapter VII, page 4.  A  process execution state where    the 
process will be inactive until a specific amount of time has passed or  an 
interrupt is received.

Sound Group -  see Chapter  IV, page 9.   Part of  an audio  block   which 
contains four  sound  units, each  consisting  of four  identical    sound 
parameter bytes and 28 data bytes.

Soundmap  -  see Chapter IV, page 25.  A memory area allocated by UCM  for 
storage of ADPCM audio data.

Soundmap  Control  Functions   -   see  Chapter  VII,  page   47.     User 
Communications Manager functions which affect soundmaps.

Sound Parameters  -  see Chapter  IV, page 9.   Filter and  range   values 
describing the characteristics of a sound group.

Sound Quality Levels  - see  Chapter IV, page  3.  Four  levels of   audio 
quality are  defined in  the CD-I  specification.  These  are   CD-Digital 
Audio with a bandwidth of 20 kHz and  16-bit quantization, CD-I Level   A, 
17 kHz bandwidth with 8-bit quantization, Level B, 17 kHz bandwidth   with 
4-bit  quantization  and   Level  C,   8.5  kHz  bandwidth   with    4-bit 
quantization.

Sound Unit  -  see Chapter IV, pages 9,  11.  A unit consisting of    four 
identical sound parameters and 28 sound data bytes.

Source Image  - see Chapter V, page 20.   High resolution, 8-bit PCM   RGB 
image which is used as the source data before compression.

Spatial Correlation - see Chapter V, page 62.  A characteristic of  visual 
images where there is  a high degree of  similarity between two   adjacent 
lines or pixels within an image.



Standard Files - see Chapter III, page 27.   Files in the CD-I disc   root 
directory with a recommended name: Path Table, Album  Descriptor,   Author 
and Manufacturer identification.

Start Flag  See Chapter II, page 7.  A  flag in the P-channel   indicating 
the start of a track.

Start Position (of a track) see Chapter II, page 7.  Position defined   on 
the absolute time  (ATIME) scale  of the CD  subcode, at  which a    track 
number changes and a new track starts.

Subcode Channel  - See  Chapter II,  page 7.   Besides  the "main"    data 
channel, 8 different Subcode Channels, called P, Q,  .... W, are   defined 
(see page 39 of the CD-DA specification).  P and Q channels are used   for 
addressing control, on disc, of the CD player  itself (head   positioning, 
etc.).

Subheader - see Chapter II, page 21.  The subheader field is contained  in 
each sector and defines file number, channel number,  submode and   coding 
information.

Submode - see  Chapter II,  page 22.  The  submode byte  defines    global 
attributes of the sector,  for instance the nature  of the data    (audio, 
video, ...) it contains.

Subsampling - see Chapter V, page 23.  The reduction of the resolution  of 
a digitized image  by (effectively)  reconstituting the image  in   analog 
form and then resampling  it at a lower  rate. To avoid  aliasing in   the 
resulting image, anti-alias filtering must be employed (see  Anti-aliasing 
Filter).

Subscreen - see Chapter V, page 13.  A horizontal strip of an image  plane 
extending the full width of the display screen, which may contain its  own 
image of a  different coding  method to other  subscreens   simultaneously 
present.  Subscreens  are produced  using the  Display Control    Program. 
(See Display Control Program).

Synchronization Detector - see Chapter II, page 38.   Part of one of   the 
units in the CD-I decoder model used for all timing needed in the   sector 
processor.








Synchronization to Display  Scanning -  see Chapter V,  page 74.   If   an 
object is repeatedly being drawn on the screen, erased and then drawn   in 
a new position, such as in some computer graphic applications, a   flicker 
effect  is  frequently   seen.   This   effect  should  be   avoided    by 
synchronizing the writing of  objects to the field  scan so that   erasure 
and re-writing takes place between successive scans of the object.

Synchronization Field - see Chapter II, page 14.  A 12 byte field at   the 
beginning of a CD-I sector.

Synchronization Primitives   -  see  Chapter VII,  page 172.   Low   level 
mechanisms for  use  by application  software  to perform  the    required 
synchronization between the video, audio and data information.

Synchronous Execution Service Request   -  see Chapter VII,  page 24.    A 
service request  for which  the process  will stop  executing  until   the 
service request has been satisfied.

System Identifier   -   see Chapter  III,  page 6.   Field  of  the   File 
Structure Volume  Descriptor  identifying  the  operating  system,   (e.g. 
CD-RTOS) to be used to access the volume.

System Modules   see Chapter  VII, page  13.  CD-RTOS  modules  that   are 
required for the CD-I system to function.  These include the kernel,  file 
managers and device drivers.

System Services  -   see Chapter  VII, page 1.   Any of  the variety    of 
facilities provided by the "system" (i.e. CD-RTOS) including creation  and 
termination of  processes,  allocation and  deallocation  of memory    and 
processing of I/O requests.

System State   -   see Chapter  VI,  page 7.   A  special  state of    the 
processor which allows execution  of privileged instructions;   synonymous 
with "Supervisor" state for the M68000 family of  microprocessors.    File 
Managers and device drivers always execute in system state.




Terminator, Terminator Record - see Chapter III, page 3.  The last  record 
in the disc label, signifying the end of the disc label.

TNO -  see Chapter II, page 9.  Track number expressed in 2-digit BCD   in 
the Q-channel of  the Compact  Disc subcode (see  page 42  of the    CD-DA 
specification).

TOC -  see  Chapter  II,  page  7.   Table  Of  Contents:  the    sub-code 
information in  the lead-in  area (of  a Compact  Disc)  identifying   the 
number of tracks, and indicating their timing, duration and mode.

Track - see  Chapter II,  page 3.  A  sequence of  contiguous data,    the 
beginning, length, mode  and end  of which are  defined in  the table   of 
contents, which is held in the Q subcode  channel of the lead-in area   of 
the disc.  The two types of tracks currently defined are the CD-DA   track 
according to the CD-DA specification and the data track according to   the 
CD-ROM specification which is also used in CD-I.  In CD-DA the length   of 
a track is related to playing times between 4 seconds and 72 minutes.

Transition Area - see Chapter V, page 70.  Relates to the partial  updates 
of DYUV images.  Here  it is necessary to  begin each line  of a   partial 
update with a transition area.  This is a  short sequence of DYUV    codes 
which have been pre-calculated to make the transition from the YUV  values 
in the surrounding image just preceding the update  to those at the   left 
edge of the update proper.  Each line of a partial update must   similarly 
be terminated with a transition area.

Transparency Control - see Chapter V, page 77.  The three mechanisms  used 
to control the transparency of superimposed image planes.

Trap Handler  - see Chapter VII,page 3.  A CD-RTOS module that   typically 
contains a set of related subroutines that is linked to by an  application 
at runtime rather than being included as part of the application module.

Trigger Bit - see Chapter II, page 23.  A bit in the submode byte of   the 
subheader that is interpreted by an application to cause   synchronization 
of various events.





U - see Chapter V, page 20.   One of the two chrominance components of   a 
video signal containing color information.

User Communications Manager  -   see Chapter VII, page  55.  The   CD-RTOS 
file manager which  provides the  software interface to  the user    input 
devices and to the video processor on a CD-I player.

User State  -  see Chapter VII, page 1.   The state of the machine    when 
user processes execute and user related requests can be processed.


V - see Chapter V, page 20.  One of  the two chrominance components of   a 
video signal containing color information.

VDSQ - see Chapter V, page 93.  See Video Data Sequence.

Video Data Sequence - see Chapter V, page 93.  The logical unit of   image 
data.  It  typically contains  the pixel  data for  a  whole image  or   a 
partial update to an image.

Video Decoder Delay - see Chapter VIII, page  12.  The time delay   caused 
by the access controller and video decoder between enabling an image   for 
display and the image appearing on the display itself.  It should not   be 
more than one field.

Video  Inquiry  Functions    -   see   Chapter  VII,  page   121.     User 
Communications Manager functions which return information related to   the 
video device. For instance, applications can obtain the data of a font  or 
the location of a region, using these functions.

Video Real-Time  Data Representation   - see  Chapter V.   The  way   that 
different kinds of visual images may be recorded on the disc, and the  way 
that this data are to be interpreted in real time by the CD-I player.

Video Sector - see Chapter II, page 24.  A CD-I sector in which the   data 
field contains video data.

Visual Coding Information Byte - see Chapter V, page 94. Contains  details 
of the coding method  and resolution of each  video data sequence.     The 
video coding  information byte  is contained  in the  subheader  of   each 
sector of the video sequence.

Volume Identifier   -   see Chapter  III,  page 6.   Field  of  the   File 
Structure Volume  Descriptor  identifying  the  name  of the  CD-I    disc 
(volume)

Volume Structure Standard  Identifier -  see Chapter III,  page 6.    This 
field of the File Structure Volume Descriptor represents the standard   to 
which the disc file structure conforms (i.e. CD-I).

Volume Structure Version Number  - see Chapter III,  page 6. Defines   the 
version number of the standard to which the disc conforms.

Wipe - see Chapter V, page 78.  The  replacement of one image by   another 
during a  period of  time by  the motion  of  a boundary  separating   the 
visible parts of the two images.

Working Directory  - see Chapter VII, page 46.   The directory   currently 
used to find data files.

World Execute (File attribute bit)  -  see Chapter III, page 21. This  bit 
of the attribute field of a directory record,  if set to one,    specifies 
that any user can execute this file.

World Read (File attribute bit)  -  see Chapter III, page 21. This bit  of 
the attribute field of a directory record, if set to one, specifies   that 
any user can access this file.


Y Component  -  see Chapter  V, page 20.   The luminance  or    brightness 
component of a video signal.

Zoom - see Chapter V, page 88.  In  video and photography the facilty   to 
enlarge (zoom-in), or diminish  (zoom-out), the area of  interest in    an 
image.

2's complement  - see Chapter II, page 3.  A method of binary notation  in 
which binary numbers are  negated by interchanging the  one's and   zero's 
and adding one to the resu lt.

625/525 Line Image Interchange - see Chapter V, page 64.  The  possibility 
to display native 525-line images on 625-line displays and vice versa.