Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~ACKGROUND OF THE INVE~TION
This invention relates to an interactive visual display
communications system and more particularly to a visual cornmunications
system using narrow bandwidth communication links between the system
terminals in which the common graphic picture on the terminal displays is
generated or modified by any one of the terminals.
Present interactive visual display communications systems
embody one of two configurations: a central computer connected to many
non-intelligent terminals or a distributed system with a number of
equally capable nodes connected together. The former arrangement is ar.
extension of the conventional time-shared computing facility where cost
is minimi~ed by placing most of the computing resources at a central
facility and a minimum of capability at the terminal. However,
difficulty arises because of low transmission speeds and poor time-shared
response. Some of the difficulty may be alleviated by providing local
processing power in the terminal but this arrangement too has its own
problems such as delineating the components to be placed in the terminal
and that of passing information between the terminal and the central
processor.
In the past, the greatest incentive for a time-shared
arrangement, or a modification thereof, was the relatively high cost of
processing power, memory and related computer components. With the
present lower costs, and the prospects for even further decreases in the
future, cost of computer components is no longer as much of a determining
factor. But the cost of communication links is still unresolved,
particularly if the amount of data to be transmitted is large.
On the other hand, present narrow-bandwidth visual
communications systems may consist of a telewriter system, a facsimile
system or a slow-scan televideo system. Of these only the telewriter
systems are interactive because long delays are incurred in the use of
the facsimile or slow-scan television frames.
There are both mechanical and electronic telewriter systems.
Mechanical telewriters use a telephone line to link two motor controlled
styli and require all visual material to be traced on the sender's
platen. Essentially, these machines only allow hand drawings to be
simultaneously traced at a distance. Electronic telewriters forego the
mechanical problems of the styli, motors and paper by outputting on a
f ". '~
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television-like display screen. Additional features such as colour,
intensity and the automatic retrieval of previously generated visual
images are possible, but in general these devices only reproduce simple
drawings at a distance. In addition, telewriter systems do not provide a
capability of interacting with the structure of the visual material.
Visual ~ata can only be handled on a line basis so that sub-sections of a
picture cannot be automatically replicated or otherwise manipulated.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a visual
communications system in which any number of physically displaced
terminals may be linked to provide a common visual display at each
terminal.
It is a further object of this invention to provide a visual
communications system in which the terminals are linked by narrow
bandwidth communication links.
It is another object of this invention to provide a visual
communications system in which an interaction at any one terminal is
immediately transmitted to all the terminals in the system to maintain a
common visual display at each terminal.
It is another object of this invention to provide a visual
communications system in which each intelligent terminal is independent
of another in that it can operate in a stand-alone mode.
It is a further object of this invention to provide apparatus
for identifying predetermined portions of a picture on a raster display.
These and other objects are achieved in a visual communications
system in which identical visual pictures are maintained at a number of
terminals linked by narrow bandwidth transmission lines. Each terminal
in the system includes visual display apparatus having a display and a
display generator, an input interactive device for providing input
instructions at the terminal and a converter coupled to the input device
for converting the input instructions to graphic task instructions. The
converter is coupled in an interaction handler which directs graphic task
instructions to a processor in the terminal as well as to a modem for
transmission over narrow band transmission lines to one or more similar
terminals. The interaction handler also receives graphic task
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instructions from the other terminals and directs these to the processor.
The processor processes the graphic task instructions for coupling to the
display apparatus whereby the picture on the display is modified and
maintained in accordance with the graphic task instructions.
BRIEF DESCRIPTION OF THE DRAWINGS:
In the drawings:
Figure 1 schematically illustrates the interactive visual
communications system in accordance with the present invention;
Figure 2 illustrates the functional structure of the
interactive visual communications system;
Figure 3 illustrates a single processor terminal
configuration;
Figure 4 illustrates an alternate dual processor terminal
configuration;
Figure 5 illustrates the function of the interactive handler;
and
Figure 6 illustrates one embodiment of a raster graphics
display unit.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The interactive visual communications system in accordance with
the present invention sets up and maintains among a group of users what
can be called a common visual space, that is, a visual picture which is
identical as seen by each user. This image does not remain static; any
user can add to or modify the picture and these changes are communicated
to all others so that their respective pictures will be modified
accordingly. The interactive capabilities of such a system can be
compared to the interaction taking when two or more people are leaning
over the same note pad or using the same blackboard. The co-operation
that can occur because of the solitary picture space or working area is
achieve~, without the necessity of physical proximity of the
communicants.
This system, as illustrated in figure 1, consists of a number
of intelligent terminals 10 which are linked together by narrow-band
lines 2, in a public switched communications facility 1, such as a
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telephone network or a telex system. Each intelligent terminal 10
includes a modem 11 or similar adaptor, a computer 12, a display 13 and
an input device 14. The modem ll, which may be any type of adaptor such
as the Bell 103 modem, connects the terminal 10 to the public
communications network 1 via line 2. The input device 14, which may
consist of one or more of the conventional input devices such as a
keyboard, a light pen, a touch sensitive device, is used by the operator
at the terminal to interact with it. The display 13, which may be either
a random vector display or a raster graphic display, such as the RGP
3000/4000/5000 manufactured by Norpak Ltd., Pakenham, Canada, displays
the graphic picture to the operator. Finally, the computer 12 performs
the function o~ an information compressor between the high bandwidth
operator-computer interface and the display-computer interface, and the
low-bandwidth computer-adaptor interface. The computer 12 may be of any
conventional type such as the Digital Equipment Corporation PDP9/15 or
PDPl1. The computer 12 at each terminal lO is used to maintain the
visual picture on the display 13 of that terminal and to perform
modifications to the picture which are requested by the operator through
input device 14 at the same terminal 10 or at one of the other terminals
10 in the system. Since each computer 12 maintains the picture on its
display 13, only the interactions of the operators need to be transmitted
through the public communications network l to each terminal lO such that
the same modification is performed simultaneously to the picture on each
display 13. For example, if the visual picture over which two
cartographers are communicating is a map, and one operator interacts with
his terminal 10 to change the projection of the map, then only the small
amount of data required to encode the interaction is transmittedJ and
each computer 12 in the system simultaneously modifies the projection of
the map on its corresponding display 13. This results in an information
concentration over a process in which the entire new picture is
transmitted or even a process wherein only the changes between the new
image and the previous one are transmitted. Thus, the communication
system in accordance with this invention maintains a common visual space,
that it, the visual picture viewed by each operator is identical, and any
one of the operators can add to or other-wise modify the picture.
Since the computer 12 is programmable, specialized features
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can be added for particular applications, and the same terminal 10 can
support, for example, a map communication system for cartographers, an
electrical circuit communication system for engineers or a symbol
communication ~ystem for the handicapped. Also because of the computer
12 at each terminal, special interaction tools, such as data processing,
can be added to each speciali~ed communication system so that, for
example, the cartographer can request that computer 12 calculate the area
of an outlined section of a map.
As discussed above, the system may include any number of
terminals 10 since there is no master-slave relationship between the
terminals 10 and thus each terminal has the capability of stand-alone
operation. In addition, although it has not been shown in figure 1, the
system can include an audio link between terminals 10 to enable voice
communications.
The functional structure of the interactive visual
communication system in accordance with this invention is schematically
illustrated in figure 2, a two-terminal system being illustrated. When
an interaction in performed by the operator using the input device 14, a
graphical task instruction or GTI is formed by the interrupt handler
represented by block 17. This GTI may, for example, represent a request
for an addition or deletion to the picture on display 13 or a data
processing request. The GTI is directed to an interaction handler 16
which receives the GTI and performs the functions of transforming the GTI
into a packet of interaction information and of channeling the GTI to its
corresponding application program processor 18 as well as to the
processor 18 in each of the other terminals 10 via the public
communications network 1. The interaction handler 16, which may be a
software module in the computer 12 (figure 1), is shown in the functional
block diagram in figure 5. The interaction handler 16 transforms the GTI
into a packet of interaction information; that is, a command for the
terminal computer to perform a given action.
The application program processors 18 in each terminal receive
the packet of interaction information, and simultaneously process it to
generate picture change information in the form of internal GTI commands
for their respective display generators 15 which control the displays 13.
These internal GTI commands to the display device 13 are not communicated
over the inter-terminal communications network 1, but are simultaneously
generated by each terminal application program processor 18 for its own
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display 13. The amount of information which is transferred over the
communications network 1 is therefore only a single packet of interaction
information while the information which is transmitted to the display may
be a large number of updates to the displayed picture.
The packets of information indicating what user interactions
occurred may be saved in a transaction table within processor 18. Data
from this table can be used to bring a third party up to date if he
enters a mu]ti-terminal conversation after it has begun, and because of
its compact nature can be used to store pictures by the method they were
created rather than by a line description. If a terminal in a
stand-alone manner has created a data-base of pictures they can be
transmitted to other terminals in this format.
All terminals can access a common data base stored on some dial
accesslble computer so that individual terminals could modify some common
data base which could then at a future date be accessed by additional
members of the working team. Since the terminals function by
simultaneously reacting to identical interaction inputs, it is essential
that the data bases upon which they operate be identical, or that they
have equal access to externally stored information.
As indicated by the size of the arrows 19 and 20, and as seen
from the above, the packet of information resulting from user
interaction, dashed line arrow 19, i8 small. This information is passed
on to the application program processor 18 in the same terminal 10 as
well as simultaneously communicated over the public network 1 to the
application program processor 18 of the other terminal. All terminals in
the system receive this interaction information. The packet of
interaction information received by the application program processor 18
of each terminal 10 is processed and the necessary changes if any, are
generated in GTI format to modify the image on the display 13. The
relative amount of information generated by the application program
processor 18 and passed on to the display 13 is indicated by the large
broad arrows 20. Thus, the amount of information transferred over the
communications network 1 between terminals 10 is only a single packet of
interaction information, whereas, the information that is passed on to
the display 13 may be a large number of updates to modify the displayed
picture.
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A terminal of the visual communications system consists of
display components, input components, communications components and a
computer component. Two preferred embodiments of this terminal consist
of a device using two computer processors to function as the computing
component, and one where a single computer processor is used to function
as the computing component. The embodiment using one computer processor
is less expensive, while the embodlment using two computer processors has
a better response and display generation speed because the computational
load is split between the two processors. Figures 3 and 4 illustrate the
single and dual processor terminal configurations respectively.
The operation of a terminal of the visual communication system
is described below. Input to the terminal 10, is entered into the
terminal via an input device 14. The interrupt handler 17, is activated
and all other operations of the process 18 are suspended while the
processor 18 handles this task. The input is classified as to the type
of interaction, and a GTI is formed encoding this information. If the
input involves selection between portions of the displayed picture a 'tag
mechanism' is used to identify which object was selected. The encoded
input is then communicated to the interaction handler 16, either directly
or over the inter-processor communications link. When communicated over
the inter-processor communications link the input is transmitted via the
modem 11 and inter-terminal communication line 2 to other terminals, and
is saved in a table of interaction inputs, and is communicated to the
application program processor 18.
The interaction table handler 30 ~see Fig. 4) records all of
the interactions that pass through the interaction handler 16 from the
interrupt handlers 17. This record may be used to analyse, at a later
date, a communication session that occurred. Also, the interaction table
handler 30 may feed the interaction GTI's to the interaction handler 16
to bring two or more communication terminals into synchronization or for
error recovery.
The application program executed by processor 18 is specially
written to suit particular applications. A special high level
programming language has been written to make the preparation of
application programs a simple task. This language has a interaction
control structure which allows the actions which occur upon interaction
inputs, to be easily defined.
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Dependent upon the application progra~ executed by processor
18, the action resultant from the interaction input may be to modify the
picture on the display screen 13. The application program executed by
processor 18 will invoke the drawing support routines 31. The drawing
5 support routines 31 are a subroutine package which convert the drawing
commands issued by the application program executed by processor 18 into
int,ernal GTI drawing codes for transmission to the display generator 15.
These codes cont~ol the display generator 15. I`he display generator
transforms each internal GTI drawing code into a low level descriptive of
the picture on the display screen 13. When the internal GTI drawing
codes are transmitted to the display generator 15 the numeric
co-ordinates for position of a drawing on the screen are transformed by
the transformation routines 32. This transforms the user's conceptual
drawing space into the real hardware co-ordinate system of the display
15 hardware 13. The functions of scaling, rotating, translating, reflecting
and clipping are performed by the transformation routines 32. This is
done using matrix multiplication techniques in software or hardware. The
display file generator 33 generates and maintains a list of display
instructions referred to on the display file 34. The display file
20 generator 33 performs the function of insertion, deletion and compaction
of the display file 34. A display driver 35 examines the display file
and maintains a picture on the display 13. The display driver 35
interprets the instructions from the display file 34 and generates the
required voltage signals to form a picture on the display 13. The
25 display driver 35 may be constructed entirely of hardware or may be a
combination of hardware and software. When using a display 13 of the
random point to point refresh type (e.g. the NORPAK ICP), the display
driver 35 must continuously refresh the display 13 interpreting
instructions from the display file 34 and is usually constructed entirely
of hardware. When using a display 13 of the raster type (e.g. NORPAK
RGP) the display driver 35 has to only generate the picture for the
display 13 once and update the picture when the display file generator 33
modifies the display file 34. In the dual processor terminal
configuration shown in figure 4, the operation of the system is
35 essentially the same. The only differences are that communication
routines 40 and 41 are used to communicate GTI's from the interrupt
handlers 17 to the interaction handler 16 and to communicate internal GTI
drawing codes from the
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drawing support routines 31 to the display generator 15. A dual
processor system is preferred because che computation load of the display
generator 15 and the interrupt handles 17 are separated from the host
computer.
Figure 5 illustrates the information flow for an interaction
input.
As has been described above, an interaction input is entered
via input device 14. The input device 14 activates the interrupt handler
17 which forms a GTI that is communicated to the interaction handler 16.
The interaction handler 16 first operates by classifying the type of
interaction. If the interaction is an identification interaction 51,
then a search 52 is made of the list of displayed material to find the
'TAG' numbert a numeric encoding of which part of the displayed picture
was identified. The 'TAG' number, or in the case of other types of
interaction the associated data, is encoded 53 in the form of a GTI code.
The interaction input is communicated as a GTI formed by
interrupt handler 17 to the communication portion of the interaction
handler 16. It is decoded 54 and a table lookup is done to determine the
object number 55. The object number 55 is a numeric encoding of which
action 59 will result from the interaction.
The interaction input is also encoded as an external GTI 56.
This encoding is done to facilitate the transmission of the interaction
information over a communications line 2 through modem 11. Error coding
and format protocols 57 are added to facilitate error checking to ensure
error free transmission of the information.
On the receiving end of the inter-terminal communications line
2 the interaction input is error checked 57 and decoded 58 9 and then
submitted to the application program executed by processor 18 in the same
manner as a local interaction input.
The communications component of a terminal of the visual
communications system is not specific. Any communications system capable
of reliably transmitting data may be used. ~eliable results have been
obtained using communications bandwidths down to 100 baud. A
communications system such as the public telephone network with data
35 access via Bell 103 modem 11 at 300 baud over dialup lines, may be used,
as well as packet switching data network such as Datapac or Infoswitch.
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The input device 14 of a terminal of the visual communications
system is not specific. Any graphical input device may be used. Some
examples of such devices are a light-pen, tablet, track--ball, oystick or
keyboard. The interaction handler 16 is designed to classify the type of
5 interaction and process it, so that any input device may be used.
The display component of the visual communications terminal may
be either a raster graphics display unit or a random vector refresh
unit. Although the technologies of both of of these units are quite
different, the display generator 15 may be modularized so 'chat either
10 display unit can be used. The raster graphics technology is pref`erred
because of the larger class of images which can be displayed.
There is some interaction between the interrupt handler 17 and
the display generator 15. IJpon an interaction input through an input
device, it is necessary for the interrupt handler 17 to determine which
15 part or portion of the displayed picture was identified. In the case of
the light-pen a signal is generated by the device 14 in kerms of the x,y
position that the pen struck the displayed picture. This positional
information is converted into an 'OBJECT' number for use by the
application program. This is done by searching a table of delimiting tag
20 55 (see. fig.5). In the case of a random vector refresh unit the
display driver is continuously refreshing the display 13 from the display
file 34 (see Fig. 4). Upon an interaction input the portion of the
display file 34 being refreshed indicates the delimiting tag and
therefore the OBJECT number. Since the display on a raster graphics
25 display unit is not continuously being refreshed, a different more
complex approach is necessary.
A raster graphics display unit 13 is illustrated in figure 6.
A standard television or high performance monitor is used as the display
61. The signals required to drive the television are derived from the
30 television signal generator 62 which continuously reads a picture memory
63. This memory is arranged as 512 by 512 bytes where the number of bits
in a byte determine the number of colours or grey levels which may be
displayed. Each of the positions is called a pixel. Since the picture
is stored in the pixel memory in positional form, the display driver 35
35 is not continuously accessing the display file 34, but builds the picture
in the pixel memory 63 once. Hardware point generators 641, line
generators 642, area generators 643 and character generators 644 are
provided in the hardware of the raster graphics display unit to aid
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the display driver 35 build the picture in the pixel memory 63. Drawing
instructions from the display file 34 are interpreted by the display
driver 35 and transmitted to the display 13 where the instruction decoder
68 determines the class of drawing command~ Either a point generator
5 641, a line generacor 61~2, an area generator 643 or a character generator
644 is invoked. The memory writing module 67 takes the output from these
generators and writes a picture in the picture memory 63.
Novel apparatus is described for the raster graphics display
unit for assigning tag numbers to interaction inputs. When a tablet or
similar positional device 14 is used for input, an x,y position is
obtained. When a light-pen is used on a raster display, a line count and
horizontal positon are obtained in terms of timing information. This is
converted to an x,y position. To convert the x,y position to a tag
number, the raster graphics display unit is placed in search mode and a
15 position comparator 66 is used. The x,y position from the input device
14 is communicated to the interrupt handler 17 and the x,y position is
saved 610 within the position comparator 66. The data is also loaded
into the x comparator register 611 and the y comparator register 612.
The interrupt handler 17 requests the display generator 15 to instruct
the display 13 to enter search mode. The instruction decoder 68 disables
further inputs by the device enable gate 69., The display driver 35 then
proceeds from the top of the display file and retransmits every point,
line, area and character. When a coincidence, within a given accuracy,
is detected by the comparators 620, 621, 622 the information which is
25 being accessed in the display file 34 at the time is recorded by the
display driver 35. The tag number is calculated from the last
coincidence in re-transmitting the entire display file if there are
intersecting pictures in the picture memory 63.
