Chapter VIII  Base Case System

VIII.1  Introduction



1.1  General


A system, made  up of  hardware and system  software, is  called a    CD-I 
system if, at the  very least, it fully  conforms to the  CD-I Base   Case 
Specification detailed  in  this chapter.  Each  part of  the  Base   Case 
Specification is mandatory in any product realization of a CD-I sytem.

It should be noted that any system (see Figure VIII.1) that contains as  a 
part of its mandatory specification the CD-I Base Case Specification,   is 
a CD-I sytem if, and only if, CD-I  disc based functions in this    system 
have priority over all other non CD-I functions  when a CD-I   application 
is active in this system.

Figure VIII.1

              ____________________________________
              _     Specification of System      _
              ____________________________________
              _ Recommended     Mandatory        _
              _ or Optional   _                  _
              _                 ________________ _
              _               _ _              _ _
              _                 _CD-I Base Case_ _
              _               _ _Specification _ _
              _                 _              _ _
              _               _ _              _ _
              _                 ________________ _
              _               _                  _
              ____________________________________


The specification  in  sections VIII.2  to  VIII.7 give  the    mandatory  
functions that a Base Case system must support. Section VIII.8   discusses 
the Base Case system resource and performance specification. This  section 
is not as yet fully detailed in the GREEN Book. It will be detailed   upon 
completion of the CD-I system validation.

1.2  Base Case Model



The Base Case model is shown in Figure  VIII.2. The CD-Control Unit,    in 
response to commands from the operating system (i.e.  CD-FM of   CD-RTOS), 
accesses the disc via the CD-DA Controller /  Decoder. When CD-DA   tracks 
are being  accessed  the  data  is  transferred directly  to  the    Audio 
Processing Unit whose function  is to control the  attenuation, set    the 
panning and output to analogue audio left/right signals.

If a CD-I track  is being accessed the  CD-Control Unit, in  response   to 
commands from the operating system (i.e. CD-FM), selects sectors from  the 
data stream and  transfers the  CD-I sectors to  the ADPCM  decoder   (for 
direct audio playback)  or, via  the system bus,  to memory  (for   audio, 
video or program related data). Audio data is usually routed  continuously 
to the ADPCM decoder  which decodes it in  real-time to produce   analogue 
audio, which is output via the Audio Processing  Unit. Video and   program 
related data as well as audio data to be stored in a soundmap is   routed, 
by means of the DMA controller or MPU, to RAM.

The RAM is organized  as two separate banks  each of a  minimum size    of 
512KB, which is  shared between  MPU and video  controller by  an   Access 
Controller.  Although the amount of memory used by CD-RTOS and the  system 
modules will vary depending upon the number of  processes active and   the 
number of open paths, it is guaranteed
at start-up of the application to be less than 64k, split evenly   between 
the two banks.  All  other RAM may be  used for either  audio, video    or 
program related data.

Video data  consists of  both pixel  data and  video  control data.    The 
display of  pixel data  from RAM  is by  means  of a  two path     display 
controller. Video data is accessed independently in the two banks of  RAM, 
and the two display paths are combined to produced a single analogue   RGB 
video output.

The operating system (CD-RTOS) is contained in ROM. Moreover, there is   a 
small area of non-volatile RAM which is available  both to the   operating 
system and application programs.


The user interface is  primarily by means of  an X-Y pointing  device.   A 
keyboard is supported, but does not form a part of the Base Case   system. 
As such, it  is the  responsibility of any  application that  requires   a 
keyboard to emulate it by means of the  X-Y device and display   functions 
if no keyboard is  connected to the system.  The latter is  known to   the 
application from the CSD table.

A standard character set and font module is provided in the system.   Also 
a clock/calendar module is provided.

Figure VIII.2
__________
_CD      _ _____________    L'i  _____________
_Player  _ _CD-DA      ___________Audio Proc._______ Lo
_A.VIII.1_ _Controller/_    R'i  _Unit       _
_- - - - ___Decoder(II)___________(IV)       _______ Ro
_Disc    _ _____________    ___ __           _
_II-VII  _   _      _            _____________
__________   _      _       _       _      _
                    _            Li _      _ Ri
           _____________    _    _____________
           _CD- Control_         _ADPCM      _
           _Unit       ___________Decoder    _
           _(VII, VIII)_    _    _(IV)       _
           _____________    _    _____________
                 _          _
                 _          _
                 __ _ _ _  __
           _____________    _    _____________    __________Ana-
            _   MPU     _    _    _Access     _    _Video   _logue
            _             ___________Controller   ______Decoder    ___RGB  
_   (VI)    _    _    _(VIII)     _    _(V)     _Out-
           _____________    _    _____________    __________put
                            _       _     _
                            _       _     _
           _____________    _       _     _
           _DMA        _    _    __________________
           _Controller ______    _RAM    : RAM    _
           _           _    _    _Bank 0 : Bank 1 _
           _(VIII)     _    _    _    (V, VIII)   _
           _____________    _    __________________
    ____________________    _    _______________________
    _     ROM (VII)    ___________NVRAM (VII, VIII)    _
    _                  _    _    _______________________
    _     CD-RTOS      _    _    _______________________
    _. Kernel          _    ______X-Y Pointing Device  _
    _. System Modules  _    _    _(VII, VIII)          _
    _. File Managers   _    _    _______________________
    _. Drivers         _    _    _______________________
    _. Trap Handlers   _    ______Clock - Calendar     _
    _. Font modules    _    ___  _(VII, VIII)          _
    _. Player shell    _      _  _______________________
    ____________________      _
                              _
 Base Case                    _
 - - - - - - - -  - - - - - - -_-  - - - - - - -  - - - - - - -  -    -   
Extension                    _  _______________________
                              ____Keyboard (VI, VII)   _
                                 _______________________

Figure VIII.2 cont'd


________    = 16 - bit Bus

________    = data & 'address' path

- - - -                                                                        = 
                                                         'control' path

The Roman numerals indicate the relevant Chapter.


VIII.2  CD-I Disc Format



2.1 General


All parts specified in Chapter II should be  supported by the Base    Case 
System.  The only additions or restrictions to this are given below.



2.2 CD-DA

A Base Case System must be capable of  decoding CD-DA PCM data, coded   in 
accordance with the CD-DA specifications, from either CD-DA  tracks on   a 
CD-I disc or CD-DA tracks on a CD-DA disc.



2.3 Mode 1

The Base  Case  System  should  be  able to  read  into  memory    sectors 
containing data with the mode byte (see II.4.4) value of 1 and   formatted 
according to the Mode 1 physical format.



2.4 EDC/ECC

The Base Case System should be able to  perform EDC/ECC for both Mode    2 
Form 1 (see II.4.7.2 and II.4.7.3) and Mode  1 sectors prior to the   user 
data being available for further processing by the system.



2.5 Sector Data Process Delay


The sector data  processing unit  (see II.6) should  process data  for   a 
real-time sector (RT-bit set to one) within 27  milliseconds.VIII.3   Data 
Retrieval Structure


3.1 General

All Base Case Systems are capable of fully processing the File   structure 
specified in Chapter III.   The only additions and  restrictions to   this 
are given below.



3.2 Mode 1


The ISO 9660 file structure is supported by the Base Case System for  Mode 
1 discs.







VIII.4  Base Case Audio



4.1 General


All parts specified in Chapter IV should be  supported by the Base    Case 
System.  The only additions or restrictions to this are given below.


4.2 Audio Mixing Control


4.2.1. Base Case System Audio Soures


The Base Case System has a mixing control unit (see IV.6.3). The  required 
tolerances for the attenuators are as follows:

Figure VIII.3

                _________________________________________
            _ Value Range       _ Tolerance         _
            _________________________________________
            _                   _                   _
            _ 0dB to 20dB       _ + 1dB             _
            _                   _ - 1dB             _
            _                   _                   _
            _________________________________________
            _                   _                   _
            _ 21dB to 127dB     _ + 1dB             _
            _                   _ - x dB            _
            _                   _   x >0            _
            _________________________________________

4.2.2  External Audio Source


Audio mixing control for external audio sources is not a part of the  Base 
Case System.




4.3 Audio Decoder Delay


The delay caused  by the  ADPCM decoder and  audio processing  unit   (see 
Chapter IV.5.1 and Figure  IV.17) should be less  than 27    milliseconds. 
This is the delay time between audio data input to the ADPCM decoder   and 
an audible output.


4.4 Audio Output


A Base Case System must have an analog stereo audio output.


VIII.5  Base Case Video


5.1  Display

The Base Case display is, at least, a  525 line (typically 60 Hz) or   625 
line(typically 50  Hz)  display with  two  fields per  frame  and   normal 
'consumer color TV' screen  resolution. If overlay of  external video   is 
required, the display must be capable of interlace. It is recommended   to 
use an analog RGB input to the display.


5.2  Color Resolution

The Base Case System must have an output digital to analog converter  with 
a color resolution of at least eight bits per R, G and B color  component, 
in order to avoid unwanted color quantization effects.


5.3  Video Functions

All video functions specified in Chapter V are  to be implemented in   the 
Base Case  System except  for those  specifically marked  as    extensions 
(related to High Resolution).


5.4  Image Coding Resolution

Normal, Double and High Resolution are defined in the Base Case  according 
to Figure V.29.


5.5  Display Control Program

In the Base  Case, Field  Control Tables (see  Chapter V.4.5.1)  have    a 
maximum length of 1024  instructions per field, and  Line Control   Tables 
(see Chapter V.4.5.1) have a size of 8 instructions per line.




5.6  Mosaic Pixel Repeat Factors


In the Base Case, the horizontal mosaic pixel repeat factor is  restricted 
to the values 2,4,8 and 16.


5.7  Mattes


The Base Case has 8 matte control registers.


5.8  Video Decoder Delay


The delay caused by the access controller and  video decoder enabling   an 
image for display and the image appearing on  display should not be   more 
than one field.


5.9  External Video Source


Although the function to  select between a backdrop  color and    external 
video is part of the Base Case System,  input and synchronization to    an 
external video source is a manufacturer's option.


VIII.6 Program-Related Data Representations


6.1 General


All parts specified in Chapter VI should be  supported by the Base    Case 
System.  The only additions or restrictions to this are given below.



6.2 Executable Object Code


All executable programs  must be  in the executable  object code    format 
specified in VI.2.1.



6.3 Character Sets


All Base Case Systems  must have a standard  CD-I character set  in   ROM. 
This character set must  conform to the specification  in VI.3.1.1.    The 
name of the default character font module must be "font8x8".





VIII.7 CD-RTOS



7.1  General


All parts specified in Chapter VII shall be  supported in the Base   Case. 
All modules specified in Chapter VII shall be contained in ROM.  The  only 
additions or restrictions to this are given below.



7.2 Kernel


All Base Case systems must contain the CD-RTOS Kernel specified in VII.1.

All Base Case Systems  must provide system clock  ticks at intervals    of 
1/100 second (_ 0.2%).

All Base  Case  Systems must  use  the startup  procedures  specified   in 
VII.1.2



7.3 File Managers


All Base Case systems must contain the following file managers:

-     Compact Disc File Manager (CDFM),
-     User Communications Manager (UCM),
-     Non-Volatile RAM file manager (NRF),
-     Pipe File Manager (Pipeman).

CDFM, UCM, NRF are specified in VII.2.2, VII.2.3,  VII.2.4   respectively. 
Pipeman is specified in  chapter 10 of Appendix  VII.1. All functions   of 
these file managers are mandatory apart from the exceptions given below.







7.3.1 CDFM I$Setstt Functions


SS_Eject          This function  is recommended.   If the CD  drive  does 
            not support a disc eject function this call  shall return  an 
            E$UnkSvc (unknown service request) error to the application.

SS_Mount          The multidisc selection function of the SS_Mount   call 
            is recommended.



7.3.2 CDFM Mode 1


The ISO 9660 file structure is supported by the Base Case CDFM for Mode  1 
discs.



7.4 Device Drivers


The device drivers  for the  CDFM, UCM, NRF  and PIPEMAN  file    managers 
specified in VII.3 are  mandatory in the Base  Case including the    above 
mentioned restrictions and additions.  These drivers provide the  software 
interface between  the manufacturers  hardware and  the low  level    file 
manager functions.  Because of the differences in hardware  configurations 
the implementation of these drivers will vary from system to system,   but 
the function- ality must  remain the same.  The  Base Case hardware   must 
provide functions necessary to implement these drivers.









VIII.8  System Resources and Performance


8.1  General


In order to  assure the  consistent functioning, from  the   application's 
point of view, of a CD-I system, a sufficient set of system resources  and 
performance attributes need be defined. It should be, however, noted  that 
the actual,  test  of the  application's  conformance to  the  Base   Case 
Systems' capabilities can only be made by 'playing' the disc in   question 
on a CD-I Base Case System. Moreover, the actual test of whether a  system 
conforms to, at the least, the Base Case System capabilities can only   be 
made by 'playing' a reference CD-I disc on the system in question.   Given 
these two points this section of the Base Case chapter specifies the   key 
system resources required by the Base Case System.


8.2  MPU


A 16-bit data bus  version of the 68000  family of microprocessors   (e.g. 
68000, 68010 or 68070).


8.3  RAM

A total  RAM (i.e.  video +  audio +  system  RAM) of  a minimum  of   1MB 
organized in at least two banks of 512KB each.

Although CD-RTOS will allocate memory dynamically on behalf of   processes 
as it expands  its internal  tables and data  structures, the    operating 
system components (kernel, file managers and device drivers) should use  a 
maximum of 64KB of RAM, split evenly between the banks.
8.4  ROM


As required to store the Base Case CD-RTOS,  the CSD and any    supporting 
library functions.


8.5  NVRAM


A non-volatile memory of at least 8KB.


8.6  DMA


A means to  transfer data  to and from  the CD-control  unit (see   Figure 
VIII.2)  and  system  memory,   that  can  perform  the   data    transfer 
independently of the  MPU once  it is activated  (e.g. a  DMA-channel   or 
intelligent coprocessor).  In addition, a means to copy contiguous   areas 
in system  memory  independently of  the  MPU (e.g.  a  DMA-channel   with 
memory-to-memory capability).



8.7  CD-Control Unit


A CD-control unit which is able to decode the subheader codes including:
      - masking of the file number
      - selecting channels and
      - channel selection for direct decoding by the ADPCM decoder
 - deinterleaving audio,  video and  program related data   streams    in 
 real-time.
   - capable of selective  interrupt generation upon receiving  any  bits 
of the submode byte.


8.8  Interrupt


All  devices  (i.e.  X-Y   pointing  device,  CD-controller  unit,     DMA 
controller, timer, video decoder) are interrupt driven.



8.9  X-Y Device


At least one X-Y device. The X-Y device must be capable of accessing  each 
pixel of the display at Normal Resolution and  must contain at least   two 
'trigger' buttons.


8.10  Clock-Calendar


The clock calendar must:
   - have a resolution of one second
   - have an accuracy of better than one minute per month.
   - be capable of counting:
        - seconds
     - minutes
      - hours         
      - days
      - months
      - years (two digit)
   - be capable of taking into account leap years.

   
8.11  CD-Player


A ready-to-use  Base  Case System  in  stand alone  form  can  have    the 
CD-player integrated into  it or,  in interfaceable form,  can have    the 
CD-player connected to  it. In  either case, it  is mandatory  that    the 
access delay from the invocation of a 'Play, CD-DA, Read or Raw'   command 
(for a given disc address) to passing the  data requested (at the    start 
address) to the CD-control unit should not be greater than 3 seconds   for 
the worst case disc seek covering the full radius of the disc.

For seeks in the proximity of the current head position (_ 20 Mbytes) a  1 
second maximum is  specified.  There  is a linear  relationship of    time 
versus distance for intermediate positions.

Note that timing for opening files is not included in the figure.