Note: Descriptions are shown in the official language in which they were submitted.
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SUBSCRIPIION TELEVISION SYSTEM AND TERMINAL FOR
ENABLING SIMULTANEOUS DISPLAY OF MULTIPLE SERVICES
~ ~.
COPENDING AND RELATED APPLICATIONS
3 This application is related in subject matter to U.S. Patent Application
;~. S Serial No. (Attorney Docket No. 1263.45972), entitled "Pay-Per-View Electronic
Program Guide", filed concurrently herewith and U.S. Patent Application Serial
No. (Attorney Docket No. 1263.45816), entitled "System and Method for
Subscriber Interactivity in a Television System", filed concurrently herewith. The
present application is a continuation-in-part of U.S. Patent Application Serial No.
10 08/073,404, entitled "Display System for a Subscriber Tem~inal", filed June 7,
1993.
EIELD OF I~I~VENl~ION
The invention p~rtains generally to CATV or other subscription television
systems, and more particularly to subscription television systems capable of
transmitting and receiving channels of information, and for enabling display of a
~: ~
combination of services simultaneously.
BACKGROI~D OF THE INVENIION ~ -
Subscription television systems can be cable television systems (CATV),
multi-point, multi-distribution subscription systems (MMDS), direct-to-home . ~ ~:
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(DTH) broaacast or satellite systems. The sophistication of communications
systems involving subscription television is continually increasing. While ~ -
providing transmission signal quality satisfactory to even the most persnickety -
; viewers, systems currently installed have greatly improved communications
capabilities and facilitate a wide variety of business arrangements between the
subscriber and the system operator. For example, such features as impulse-pay-
. ..
per-view, various conditional access schemes, addressable messaging systems and
~¦ other text services, and electronic prograrnming guides, to name just a few, may
be supported.
In order to provide and enable operator control of such services, a
- multitude of apparatus is required. As a result, subscription television systems
have become increasingly complex. For example, the subscriber terminals have
conventionally provided the functions of tuning particular channels of the
subscription system which are outside of the subscriber's television receiver
capability. Fur~er, they provide conditional access to particular subscription
service through authorization of particular channels of service by descrarnbling. ~ :
More recently, the subscriber terninal has become user friendly by
providing an interactive, on-screen display and other user functions that allow the
subscriber to manipulate the cable service and his television receiver in additional
ways. These features include volume control, sleep timer features, parental
control capabilities, program timers for recording programs on a video cassette
recorder (VCR) and other types of consumer-friendly operational features.
An advantageous example of a subscriber terrninal with advanced consumer - ~
: -
features is the Model 8600 series of subscriber terminals manufactured by
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Scientific-Atlanta, Inc. of Norcross, Georgia. These terminals generally provideon-screen displays by combining the video signal from a selected channel with anon-screen display video signal from a video generator p1ior to remodulation of the
J combination to either Channels 3 or 4. In addition, a more sophisticated example
of an on-screen display in a subscriber terminal is discussed in U.S. Patent
Application Serial No. 08/073,404, filed June 7, 1993, entitled "Display System
for a Subscriber Terminal", which is incorporated herein by reference.
Despite the recent advances, there remains a general need to provide new
? and additiona~i services and features to satisfy the eclectic tastes of subscribers. In
addition, there is a need to make existing systems even more user-friendly.
Further, there is a need to provide a variety of services without increasing
bandwidth requirements. In conventional subscription television systems, a
broadband television signal having a plurality of 6 MHz frequency channels is
generated at a headend and transmi~d via a distribution system to subscriber f~
terminals. Each of the 6 MHz frequency channels includes video and audio
information corresponding to a discrete television (TV) program. Accordingly, totransmit four TV programs, for example, 24 MHz of bandwidth is required.
. When the user selects a service channel for viewing, the subscriber ~erminal tunes
to the corresponding frequency channel, and video and audio information
! 20 associated with the selected service channel is displayed.
Multi-service communications systems transmit different services over one
f or more different frequency channels thereby providing additional service without
a corresponding increase in transmission bandwidth. Each frequency channel may
carry text services in addition to video and audio information that compose a
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standard TV service. Therefore, to gain access to a text service, a subscriber
terminal must have information to tune to the frequency channel carrying the text
service and information to select the desired text service from the several textservices and the TV service provided on that frequency channel.
S U.S. Patent No. 4,908,859 to Bennett, entitled "Receiver Access Interface
to Service Components in Television Channel" discloses a receiver interface
system that stores a service definition table, a service-to-channd map, and a
channel configuration map. The service definition table defines the relation
'1 between service components and service numbers. The service-to-channel map
defines the relationship between service numbers and interface channel numbers.
The channel configuration map defines the relationship between frequency channels
and interface channel numbers. Using these relationships, a receiver can locate
and access a service selected by a user in signals transmitted over various
frequency channels.
U.S. Patent No. 5,200,823 to Yoneda et al., entitled "Virtual Channels for `
a Multiplexed Analog Component (MAC) Television System", contains a
description of a television system for providing services, including video, audio,
and text services, to remotely located subscribers over a plurality of channels. A
decoder at the subscriber location receives audio, video, and text components over
each physical channel. The decoder contains a mapping of each physical channel
to virtual channel numbers. Each virtual channel may use a different combinationof components. For example, one virtual channel may comprise linked pages of
text service. A user can select a virtual channel using a selector and thereby
receive the combination of service components defined by the virtual channel.
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Many viewers desire to view multiple services simultaneously. In addition,
subscription television operators recognize the benefits of providing multiple
services simultaneously to subscribers. One known solution is to provide
, subscribers with two subscriber terminals in a master-slave relationship. The
subscriber terminals may be linked to each other via a serial data port or oth~rinformation connection. The incoming cable carrying the broadband television
,~ ~
signal is input to an RF splitter having outputs to each of the master and slavesubscriber terminals. All control functions can be performed by the master
subscriber terminal. For example, the masta subscriber terminal may be used to
10 control the tuner of the slave subscriber terminal. The user can control the tuners
in each subscriber terminal to tune to the different frequency channels which carry
the two programs that the user wishes to view.
For example, the output of the subscriber terminals is supplied to a picture-
in-picture capable television set. Accordingly, the user can view two different
programs simultaneously. This arrangement would, in addition, allow a user to
..
record one program selection on a VCR or like recording device while
simultaneously viewing another program selection simply by connecting the outputof one of the subscriber terminals to the recording device.
However, it is e~pensive for each subscriber to purchase or lease two
subscriber terninals. In addition, providing the information to support two
services on separate channels reduces the bandwidth available for other purposes.
Accordingly, there is a need to enable subscribers to view multiple programs
simultaneously without increasing the transmission bandwidth.
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- SUMMARY OF THE INVENTION
. .,
It is an object of the present invention to provide a subscription television
system that is both highly user-friendly and capable of supporting additional
, .
~' features.
It is a further object of the present invention to provide a system for
transmitting multi-ærvice channels, inciuding video, audio, and text services, and
enabling display of a combination of services simultaneously.
It is a further object of the invention to provide a system for transmitting
a channel of service, including a composite of several video services and one ormore text services, and enabling display of a combination of the video services and
text services.
It is a further object of the invention to provide a subscriber terminal
apparatus that his highly user-fr;endly and that is capable of supporting additional
features.
~ . .
It is a furtha object of the present invention to provide a subscriber
terminal for receiving multi-service channels9 including video and text services,
and enabling display of a combination of services simultaneously.
It is a ~urther object of the invention to provide a subscriber tenninal for `~
receiving a channel of service, including a composite of a several video services
:~
and one or more te~t services, and enabling display of a combination of the video
services and text services.
In accordance with the present invention, a subscription television system
includes a headend that transmits a broadband television signal having ~nultiplechannels of information via a distribution system to at least one subscriber terrninal
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remote from tne headend. The headend includes a video combiner that combines
several video signals into a composite video signal. Each of the video input
signals to the video combiner corresponds to a different video program. The
headend additionally includes a circuit that inserts text data streams into the
composite video signal. For example, text data streams may be inserted into the
vertical blanking interval or carried as amplitude modulation of the sound carrier
of the composite video signal. The composite video signal is then modulated ontoa channel of the broadband television signal which is transmitted to the subscriber
terminal. Moreover, additional information, for example text data streams, may
be transmiKed over a dedicated out~f-band channel, for example, at 108.2 MHz.
The subscriber terminal includes a selector for selecting a virtual channel
and a control signal generator for generating tuning control signals, text data
extraction control signals, and video program control signals corresponding to the
selected virtua1 channel. A tuner tunes to the channel of the broadband television
signal carrying the composite video signal responsive to the tuning control signals.
Processing circuitry processes the composite television signal received from thetuner. The processing circuitry includes a text data extractor that extracts a text
data stream from the composite video signal in accordance with the data extraction
control signals.
The subscriber terminal additionally includes an on-screen display control
that generates a video output display signal. When the video output display signal
is input to a standard television receiver, the television displays text information
from the extracted text data stream and video information corresponding to the
video prograrn deterrnined from the video program control signals.
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The composite video signal may be formatted such that the picture is
divided into quadrants, with a different one of four programs in each quadrant.
For example, the on-screen display control can produce a video output display
.,,i , .
signal such that one of the four programs appears in one quadrant of the displayed
picture and text mformation appears in the other three quadrants of the displayed
picture. Consequently, from a single channel of the broadband television signal,several multi-service virtual channels may defined, each having a different
combination of video and text.
In addition, the present invention provides a subscription television terminal
10 that receives a broadband television signal having a composite video signal on one
channel thereof. The composite video signal is formed from the video signals of
a plurality of video programs, and includes text data strearns. For example, thecomposite video signal may be formed fiom video signals of four different video
programs. The composite video signal is formatted such that the four video
15 programs would appear without distortion in a respective quadra~it of the television
display. The te~t data streams may be inserted into the vertical blanking interval
of the composite video signal.
The subscriber terminal includes a memory that stores a mapping of a
virtual channe1 to the channel of the broadband television signal that the composite
20 video signal occupies. In addition, the memory stores a mapping of the virtual
,. . ~ ..
channel to a combination of a te~t data stream and a por~on of the composite
video signal that corresponds to one of the video programs.
. ~ :
When a selector selects the virtual channel defined in memory, a tuner
tunes to the channel of the broadband video signal that the composite video signal
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s occupies as determined from the mapping in memory. Accordingly, the composite
video signal may be applied to processing circuitry. In the processing circuitry,
the text data stream corresponding to the selected virtual channel can be extracted.
The extracted text data stream and the composite video signal are then supplied to
S an on-screen display control which produces a video output display signal
therefrom. When applied to a standard television receiver, the video output
display signal produces a picture having both text information from the extracted :
data stream and video information from the portion of the composite video signalcorresponding to the video program defined by the virtual channel.
Accordingly, the present invention enables display of multiple services of
text and video simultaneously without requiring an additional tuner and without
occupying more than a single band of the broadband television signal.
Furthermore, the present invention enables several different virtual channels to be
defined from the composite video signal. Accordingly, numerous different
services may be provided to the subscriber without a corresponding increase in
bandwidth. ~
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BRIEF DESCRIPIlON OF T~IE DRAWINGS
A more complete appreciadon of the present invention and many of the
attendant advantages thereof will be readily obtained as the invention becomes
~ 20 better understood by reference to the following detailed description when
] considered in connection with the accompanying drawings.
Figure lA is a detailed diagram of a subscription television system
according to the present invention.
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Figure lB illustrates an embodiment of a video combiner according to the
"~ present invention.
Figure lC provides a representation of a display of the composite video
signal output from the video combiner illustrated in Figure lB.
S Figure 2 is a detailed black diagram of one of the subscriber terminalsshown in Figure lA. ~ :
Figure 3 illustrates an embodiment of the VBI data decoder shown in -;
. . ~ ::
Flgure 2. ; -~
Figure 4A illustrates the display obtained from a virtual channel composed
.,
of video #1 and text stream #3.
Figure 4B illustrates the display obtained from a virblal channel composed
of video #3 and text #1.
Figure 4C illustrates the display obtained from a virtual channel composed
, . .
of video #4 and text stream #2.
Figures 5A and SB illustrate the menu screen used in connection with the ~ ;
message processes.
. DETAILED DESCRlPllON OF THE ~F~RRED E~IBQPIM13 NTS
Figure lA is a detailed diagram of a subscription television system
~ -.:
according to the instant invention. The system of Figure lA is intended to serveas an example and should not be construed as limiting the invention. A central
control center 10 orchestrates the operation of the subscription television system.
.
Central control center 10 is often associated with the central office of a multi-
service operator and may communicate with and control multiple headends, such
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.~ as headend 12. Headend 12 provides a subscription television service to a local
area, for exarnple, a city or a group of cities or towns.
A subscriber terminal 14 is also shown and may be located in a subscriber's
home or business location 70. Subscriber terminal 14 is coupled to VCR 18 and
television 20. It should be clear that the subscriber terminal 14 can also be
coupled directly to the television 20 as shown by dotted line. Information may be
communicated between central control center 10 and headend 12 by any known
means including telephone networks, satellite transmissions, optical fibers, coaxial
cable, other transmission lines, telecommunication apparatus, etc. or any
combination of known means. Headend 12 may be coupled to subscriber terminal
14 via a subscription television distribution system 58, for example coaxial cables,
satellite, optical fibers, telecommunication apparatus, or other known means or
combinations of known means.
Central control center 10 includes a system manager 22 that directs the
other components of central control center 10. System manager 22 preferably
comprises a Scientific-Atlanta system manager 10 network controller. Central
control center 10 may, for e~cample, provide billing services for the provider,
including billing for pay-per-view events. A billing computer 24 stores billing
data and may also format and print bills. Modems 26 and 38 allow data
transmissions between system manager 22 and headend controller (nHEC") 28 of
the headend 12. BC 28 preferably comprises a Scientific-Atlanta Model 8658
headend controller. For example, authorization data may be transmitted from
, : :
system manager 22 to HEC 28. HEC 28 formats the authorization data and
transmits it to subscriber terminals either in-band through scramblers 48, 50 or 52
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or out-of-ban-, through outband data transmitter 54. Billing data from the
subscribers can be received through either phone processor 30 or modem 32.
Subscriber terminal 14 can either transmit billing data over a telephone line
directly to the phone processor 30 or back up the cable to RF lPPV processor 34.S If the data is sent to RF IPPV processor 34, it is sent by modem 36 associated
with RF IPPV processor 34 to modem 32 associated with system manager 22.
System manager 22 accumulates the billing data from phone processor 30 and - ~-
modem 32 and provides it to billing computer 24 so that customers may be billed
for their program services.
~':
An electronic programming guide (EPG) data provider 16 supplies ~-
television schedule data to headend 12 via satellite receiver 40 or by other known
~ . .
means such as, but not limited to, cable, optic~ fiber, and telecommunications.
This data includes program information arranged by time and channel. One such
service is offered by Insight Telecast Inc. The Insight service provides extensive
television program listings. Cable operators can purchase this data and provide
it to their subscribers.
The EPG data received by satellite receiver 40 is passed to information
service processor 42. Information service processor (nISP") 42 may also receive
te~t data for transmission to subscribers. The text data may include weather
information, sports scores, messages, etc. and may be provided by an informationservice provider, or accumulated or generated by the system operator. ISP 42 is
responsible for receiving the EPG data, as well as the other data, formatting it,
and transmitting it to the subscriber terminals. ISP 42 provides data to scramblers
44 and 46. Of course, the actual number of scramblers to which the ISP provides
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data may dep~nd on the amount of data to be transmit~ed, the number of channels
on which the data is to be transmitted, and the frequency at which one wishes tosupply the data to the subscriber terminal. The two scramblers 44 and 46 in
Figure 2 are for example only. Scrarnblers 44 and 46 place data in-band for
transmission to subscribers, along with scrambling an associated television signal.
The EPG data and text data in a preferred embodiment are placed in the vertical
blanking interval, but may also be placed elsewhere in the 6 MHz channel of an
NTSC television signal. While an NTSC (U.S. standard) television signal is
described by way of exarnple in this description, the signal may be PAL, SECAM,
a digital video compressed signal, or a high definition television signal having a
wider bandwidth. For example, the data could be placed on the sound carrier or
transmitted over a separate out-of-band channel (not shown). Additional
information concerning ways to transmit the data may be obtained from U.S.
Patent Application Serial No. 07/983,766, entitled "In-Band/Out-of-Band Data
Transmission Method and Apparatus for a Television SystemN, incorporated herein
by reference, U.S. Patent Application Serial No. 07/799,987, entitled "Method and
Apparatus for Message Information~, filed November 29, 1991, which is
~,~ incorporated by reference, and U.S. Patent Application Serial No. 07/800,241,
entitled ~Method and Apparatus for Tuning Channels in a Subscription Television
System having In-Band Datan, filed November 29, 1991, which is incorporated by
, reference. Also, further inforrnation concerning EPG and pay-per-view processing
`~ can be obtained from U.S. Patent Application Serial No. (Attorney Docket No.
1263.45792), entitled "Pay-Per-View Electronic Programming Guide", filed
concurrently herewith and incorporated by reference.
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The E~G data received by satellite receiver 40 will often be very extensive,
, .3 ,
containing data for prograrns up to one or two weeks in advance. If all this data
is to be transmitted to subscriber terminal 14, the terminal must be able to store
the data in its memory. To store that much information requires a significant
5 amount of memory which would greatly increase terminal costs. Thus, ISP 42 canselect portions of the data to be transmitted to subscribers. ISP 42 receives the
'-~ EPG data, selects the portion to be transmitted to subscribers and passes that
. ~ . . ..
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portion to a scrambler, e.g. scrambler 44 and/or 46. Not only may ISP 42 select
portions of the EPG data, but it may also add data on local stations not covered10 by EPG data provider 16. ISP 42 may also reformat the data in such a way as to
make it more pleasing to the subscribers.
Data is most conveniently tagged as short term or long term, for example,
to scramblers 44, 46. Scramblers 44, 46 send more immediate data, for example,
the next several hours of EPG data more frequently (at a higher repetition rate)15 than long term data. For this purpose, scramblers 44, 46 are provided dynamicrandom access memory (DRA~, for example, at 256 kbytes, 512 kbytes, or 1
Mbyte, for storage of data.
~ As discussed above, ISP 42 may also obtain text data from an information
-1
service provider, such as a stock quote service, or generate text data locally. The
20 text data may received via satellite, dial up modem, direct connect modem, direct
connect to system manager, or other hlown means. The text data may either be
transmitted as received or reforrnatted by ISP 42, then transmitted to a scrambler
(44 or 46) for transmission to subscribers as described above.
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ISP 4~ also passes data to HEC 28, which controls scramblers 48, 50 and
52, and also outband data transmitter 54. The scramblers 48, 50 and 52 scramble
television signals and may also insert in-band data. The television signals may be
re eived via satellite receiver 40, as shown, or by other means such as local
S broadcast, microwave, coaxial cable, optical fibers, telecommunication apparatus,
etc. or a combination thereof. Before applying the television signals to the
scramblers, the video portion of several television signals may be applied to a
video combiner 64 to produce a single composite video signal. This will be
described in greater detail in connection with Figures lB and lC. The audio
portion of the television signals may be applied directly to the scrambler. Of
course, video combiners may supply the input to any number of scramblers
Further, scramblers 48, 50, and 52 may contain memory for storage of data for
transmission. Scramblers 44, 46, 48, 50, and 52 may be Scientific-Atlanta Model
8656 line scrarnblers. Also data may be transmitted on non-scrambled channels
via data repeater (not shown) such as a Model 8556-100 data repeater.
The outband data transmitter 54 transmits data on a separate carrier, i.e.,
not within a 6 MHz channel, for example at 108.2 MHz. The transmitted data
may be, for e~ample, descrambling information. In a preferred embodiment, data
is inserted in each vertical blanking interval to indicate the type of scrambling
employed in the next video field. Further, authorization information could be
transmitted; this information would authorize the reception of channels or
programs. Some of the information transmitted would be global, i.e., every
subscriber would get it. For example, the descrambling information could be a
global transmission. Note that just because each subscriber receives the
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descrambling inforrnation does not mean that eacn subscriber terminal can
descramble ~he received signal. Rather, only authorized subscriber terminals
would actually be capable of descrarnbling a received signal. ~ ~ -
On the other hand, data transmissions may be addressed transmissions.
S Authorization data would normally be addressed to individual subscribers orgroups of subscribers. That is, when transmitted, the data will have an address
(for example, a subscriber terminal serial number) associated with it. The
subscriber terminal addressed will receive the data and respond accordingly. Other
subscriber terminals will ignore the data. The outputs of scramblers 44, 46, 48,50, 52 and outband data transmitter 54 are passed to any necessary processing
equipment, such as signal processors, modulators and combiners. These elements
are generally indicated as block 56 and do not form a part of the instant invention.
A distribution system 58 leads to a subscriber location 70. - -
At the subscriber location 70, terminal 14 is found. In Figure lA, for
example only, one subscriber terminal is sho vn. Typically, at given location only
one terminal will be found. However, two terminals may be provided Figure lA
to indicate that different types of terminals may be used in the same system as
discussed in greater detail below. At the subscriber location, subscriber terminal --
14 is connected to the subscriber's video equipment, including, for example, a
VCR 18 and television 20.
As illustrated in Figure lB, the video combiner 64 includes an input from `
each of, for example, video source #1, video source #2, video source #3, and
video source #4. Of course, any number of video sources may be applied to video
combiner 64 consistent with the present inven~on. Video combiner 64 reformats
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the video sources #1-#4 to produce a composite video signal. For example, for
the first half of each field of the composite video signal, the video information
from the video source #1 may comprise the first half of each line of active video
and video information from the video source #2 may comprise the second half of
S each line of active video. For the second half of each field, the video information
from the video source #3 may comprise the first half of each line of active video
and video information from the video source #4 may comprise the second half of
each line of active video. A control signal from HEC 28 may be provided to
select the order in which the video signals are combined to produce the output
from the video combiner 64.
Figure lC provides a representation of a display of the composite video
signal discussed above. As shown in Figure lC, the overall picture is a composite
of the pictures of the four individual video sources #1-#4, each picture located in
a separate quadrant of the overall picture. Consequently, the aspect ratio of each
picture remains intact and distortion is minimized. One or more audio signals may
be added to the composite video signal at the scrambler depending upon
transmission limitations. The composite video signal may additionally be
multiplexed with one or more text data streams, for example, by inserting the text
data streams in the vertical blanking interval of the video. Of course, the text data
streams should not be considered limited to merely data representing text, but may
include other data information, such as graphics data or control data, for example
It is merely the manner in which the data is interpreted that determines its content
As is clear from the above description, a single composite video signal
includes the information equivalent of four video signals, but is transmitted to
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subscriber terminals utilizing only 6 MHz of bandwid~ll. However, the composite
video signal ~ransmitted from the headend is not limited merely to video
information, but may include text data streams and audio signals, among other
information. This additional information would generally be included after output
from the video combiner 64.
Furthermore, the ISP 42 may receive data transmitted from a subscriber via
a return path, e.g. RF IPPV Processor 34, via modem, optical transmitter, etc.
The data may comprise text data or data representing other information fonns,
such as audio information and/or video image(s) obtained from a camera at the
subscriber's premises, for example, built into the subscriber terminal 14. The data
received from the subscriber may be associated with the address of another
subscriber or group of subscribers. The ISP 42 may transmit this data to the
scramblers in a manner similar to message data. Accordingly, one subscriber
would be able to transmit messages to another subscriber or to a group of other
subscribers. If the data represents a video image, for example, occupying 1.5
MHz of bandwidth, the subscribers receiving the message can obtain an image of
the subscriber sending the message and/or audio and/or text information, all of
which forming the message. In the manner discussed below, such message
information may be overlayed onto the picture of the channel selected for viewing
by the receiving subscribers.
Referring to Figure 2, a detailed block diagram of one of the subscriber
terrninals will now be described. The broadband television signal from the signal
distribution system 58 is received at the input of up/down converter or tuner 100.
To provide for picture-in-picture capabilities or simultaneous watch and record, for
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example, multiple tuners (not shown) may be provided for tuning to more than onetelevision channel simultaneously. An out-of-band data receiver 150 is also
coupled to the broadband input. Conventionally, the up/down converter 100 may
include an input filter, such as a diplexer, to separate the 108.2 MHz out-of-band
signal and the broadband television signal. The up/down converter 100 can be
tuned to a predetermined data carrying channel for receiving in-band video and
7 audio data when used by the subscAber for recording or viewing a selected
, channel. The channel may be predetermined from the system manager 22 and, by
one of the data transmission methods described herein, the predeterrnined channel
identification can be stored in the subscriber terminal 14.
When in use, the up/down converter is tuned according to a channel
selected by a subscriber via a user interface having ar. infrared (IR) receiver 124,
remote control 126, and/or terminal keypad 122. Up/down converter 100 uses a
phase locked loop under the control of a tuning control 102 to convert the selected
orpredetermined defaultRF channel signal to a45.75 MHz intermediate frequency
signal. A multifunction control circuit (MCC) 104 is linked to up/down converterby a bidirectional link to the tuner control 102. The MCC 104 is preferably an
application specific integrated circuit (ASIC) combining many subscriber terminal
control and data handling functions into a single package. Of course, the ASIC
may include any combination of individual control circuits. Alternatively or in
addition, other control circuitry may be used, fore~ample a micropro essor.
The bidirectional link may include one path for tuning and a return path for
feedback control of the tuning process. A feedback signal for automatic gain
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control and one for automatic frequency control are transmitted to the up/down
converter 100 through filters 101, 103, respectively from a video demodulator 109.
A filter, for example a SAW filter 106, filters the IF channel signal to split
the signal into separate video and audio portions for processing. The video portion
is demodulated and descrambled by the video demodulator 109 under the control
of the descrambler control 110 of the MCC 104. For example, the video
demodulator 109 may perform sync restoration (one form of descrambling of the
video signal) for sync suppression scrambling. The video signal then passes
. ~ . .
through a bandpass filter 130 to an on-screen display control 132 where inverse - -
video inversion (descrambling) takes place if necessary. The descrambling of the ~ - -
- ~
video portion, whether sync suppression, sync inversion, video line inversion, etc.,
is under the control of the descrambler control 110 of the MCC 104. The -;~
descrambler control 110 provides the necessary timing signals, inversion axis
levels, and whether the video is inverted or not to the on-screen display control -
132 and supplies the necessary timing, restoration levels, and identification sync ;
pulses to be restored to the video demodulator 109. The descrambler control 110 - `
receives such descrambling information either from pulses as in-band audio data
or from data modulated on the video during the vertical blan~ng interval or via - ~
out-ofband signals. ~ -
In the other path, the audio signal is converted from the 41.25 MHz IF -
carrier to the intermodulation frequency of 4.5 MHz by a synchronous detector
105. Feedback for automatic gain control of detector 105 is supplied from the
output of bandpass filter 161. The audio signal may then be demodulated by an
FM demodulator 119. An amplitude modulation detector 111 performs pulse
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,
detection to recover the in-band audio data which are amplitude modulated onto
the audio carrier. The received in-band pulses are supplied to an in-band audio
data decoder 117 of MCC 104 for processing after being shaped by pulse shaper
115. The in-band data, except for descrambling data, is stored in DRAM 137 for
S buffering. Descra nbler control 110 accesses descrambling data directly for the
video descrambling operation. -
~, -
Volume control of the audio signal is performed under control of a volume
control 41 and the microprocessor 128 as described in U.S. Patent No. 5,054,071,~' incorporated herein by reference. After volume control, the audio signal is passed
through a low pass filter 123 and a mute switch 125. The output of the mute ;~
switch 125 is applied to a modulator 142. ~- -
3 The MCC 104 receives the video signal after demodulation and -
descrambling and detects the in-band video data from the VBI of the signal with
a VBI detector. The in-band video data is transmitted at a frequency on the order
of known teletext systems, such as 4.0 megabits per second. However, the
invention should not be considered limited in this respect. A data clock provides
-
an appropriate sampling frequency higher than the Nyquist rate according to well3 known techniques. The VBI data decoder 129 stores the data in DRAM 137 prior
to processing by the microprocessor. Additional details of the VBI data decoder
.t 20 will be discussed in coMection with Figure 3.
The on-screen display control 132 selectively generates on-screen character
-, and graphics displays in place of or overlaid on the video signal. For example,
-, the information stored in DRAM 137 by the VBI data decoder 129 may be read
', out to the on-screen display control and used to generate on-screen characters
.`'
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and/or graphlcs. The modulator 142 combines the vlaeo signal from the output
of the on-screen display control 132 and the audio signal from the output of the -
mute control circuit 125 and converts the combined signal to the channel freqliency ~ ~ -
se1ected by the microprocessor 128, such as channel 3/4 for NTSC. The combined ~
", .: ,.,
and remodulated signal is supplied as an RF output to a television receiver in a ~ -
well known manner. ~ -~
- : -,
A control microprocessor 128 controls the overall operation of the
subscriber terminal 14. The subscriber terminal communicates to and controls themicroprocessor 128 through interactive user interface with an on-screen display.The user interface includes keyboard 122 on the front panel of the subscriber
terminal 14 and the remote control 126 which generates subscriber control signals
for channel tuning, volume level control, feature selection, and the like. Thesesubscriber commands are decoded by an input scanner and control 148 of the
MCC 104. The remote IR receiver 124 of the user interface receives the
commands from the IR or other remote control 126, as is well known in the art,
and provides commands to the microprocessor 128. The user interface may
additionally include a display 120, for example, a four-digit, seven segment LEDdisplay, which displays the tuned channel numbers and diagnostics.
When the keypad 122 or remote control 126 is utilized to select a
command, the microprocessor 128 operates to e~ecute the command. The
subscriber terminal interacts with the subscriber by providing numerous on-screen
displays which assist in the operation of the terminal. The on-screen displays
provide information and prompts to guide the subscriber through many of the
complex features of the terminal. For example, the on-screen display may
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implement a menu page structure for providing screen-by-screen directions for
using the subscriber terminal and its features.
The descrambler control 110 of the MCC 104 utilizes recovered
I
descrarnbling data to generate appropriate control signals, for exarnple, inversion
S control and equalizing, sync restoration or regeneration for descrambling, or
otherwise resto~ing the input baseband television signal. A secure microprocessor
136 determines whether the descrambler control 110 of the MCC 104 carries out
descrambling on a particular channel or what forrn of descrambling is required at
a particular time by interpreting the authorization and con~rol data downloaded
from the system manager 22 (by any of the three data transmission schemes
discussed herein, out-of-band, in-band audio or in-band video) into the internalnon-volatile memory (NVM) of the device. The NVM in the secure
microprocessor 136 stores secure data, for example, authorization data, scrambled
channel data, some terminal configuration data and other required data.
The control processor 128 operates by running a contrd program which
preferably is par~ally stored in a read-only memory intemal to the processor andpartially stored in an NVM, such as Flash EPROM memory 134. In addition, the
control program of the microprocessor 128 may also reside in the NVM of an
expansion card 138. The control program may be downloaded from the headend
12 in the manner discussed in U.S. Patent Application Serial No. 07/983,909,
entitled "Reprogrammable Subscriber Terminal", filed December 1, 1992, which
is incorporated by reference. The microprocessor 128 communicates with the
NVM 134, 138 via a memory bus 141 which has data, address, and control lines
The microprocessor 128 also controls the data decoders 117, 129 and 146, volume
.. , . .. . . .. - . ,, , . , ,~., . ~ . ... .... , : :
21~301
... .
control 41, on-screen display control 132, and the tuner control 102, descrambler
control 110 and input key scanner and control 148 via commands through MCC
!`~ 104 and control processor bus (CMB) 131. The microprocessor 128 directly ;
`3 controls the mute switch 125 and the output frequency selection of the modulator
142. The microprocessor 128 includes additional capacity for other auxiliary
~ . .
device communications and control through a data port 140. For example, the
data port may accommodate an IR blaster for VCR control via an on-screen menu,
an additional subscriber terminal for dual tuner operation, or connection to a
digital video subscriber terminal.
-. -~
The subscriber terminal 14 may receive addressable and global data, other
text data, and descrambler data transmitted from the headend 12 via the in-band
vertical blanking interval (VBI). Alternatively or in addition, addressable and
global data may be transmitted in a separate out-of-band data carrier if an out-of-
band receiver is provided. The memory control 112 permits data coming from the
three data decoders 117, 129, and 146 to be placed in a volatile memory, for
example DRAM 137. There it can be accessed by the control microprocessor 128
via the CMB 131. Additional details are discussed below. The MCC 104 also
distributes control instructions from the control microprocessor 128 to other parts
of the MCC 104 to provide operation of the rest of subscriber terminal 14. The
MCC 104 additionally coMects to a secure microprocessor bus (SMB) 143 which
permits communications between the secure microprocessor 136 and otherpor~ons
of the subscriber terminal 14. The SMB 143 is further coupled to the expansion
card 138 to provide renewable security.
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The memory control 112 and microprocessor interfaces of the MCC 104
are the central communications facility for the control microprocessor 128 and the
secure microprocessor 136. The memory control 112 receives requests from the
microprocessors 128, 136 and other controls and data decoders to write to memoryor read from memory. It resolves contentions for memory transfers, giving
priority to real time applications and the micr~processors, and schedules the data
flow. Themicroprocessors 128, 136communicatethroughinternalregisters ofthe
MCC 104 with the memory control 112 and other portions of the MCC 104.
The expansion card 138 may be a printed card which contains memory
and/or secure rnicroprocessor components, which can be plugged into a connector
200. The connector 200 can be configured such that, when it receives the
expansion card 138, the expansion card is flush with top cover. The connector
200 electrically extends the control microprocessor memory bus 141 and the secure
microprocessor bus 143 to the expansion card 138. Additional program or data
memory, renewed security, or any other application supported by microprocessors
128, 136 can be provided by the expansion card 138. In addition, circuitry
coupled to microprocessor 126 may be provided for detecting whether or not the
expansion card is installed. Thus, the subscriber terminal 14 may be controlled
in accordance with information contained on the expansion card 138 when installed
and in accordance with internal software when the expansion card 138 is not
installed. Additional detai1s concerning the e~cpansion card 138 may be obtainedfrom U. S. Patent Application Serial No. 07/983,910, entitled "Subscriber Terminal
with Plug In Expansion Cardn, which is incorporated herein by reference.
:;
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The subscriber terminal may optionally include an impulse-pay-per-view
(IPPV) module of the telephone type 252 or of the RF-IPPV type 154.
Alternatively, such reverse path information may be transmitted via an optical link,
or other known means. The IPPV module allows subscribers to request
authorization of their subscriber tenninal to receive pay events such as pay-per-
view events or near-video-on-demand (NVOD) transactions, store the data
associated with the purchase of the event in the NVM of the secure microprocessor
136, and then transmit the data to the system manager 22 via the telephone return
path or the RF return path via the signal distribution system.
Furthermore, "interactive television" inforrnation rnay be transmitted to the
system manager 22 via the RF or telephone IPPV module or other reverse path
transmission. In such case, the subscriber terminal may receive information
defining a menu which may be immediately displayed. When the user responds
to a menu prompt, the resulting information may be immediately transmitted as
return data. For example, the user may respond to a poll by entering informationto the keyboard. The results of the poll may be determined at the head end and
later reported to the subscriber terminals. Additional details concerning the
interactive television features can be obtained from U.S. Patent Application Serial
No. (Attomey Docket No. 1263.45816), filed concurrently herewith, and
incorporated herein by reference.
Figure 3 illustrates the VBI data decoder 129 in greater detail. The VBl
data decoder 129 performs two main functions. The first function is to process all
scrambled transactions that are sent to the subscriber terminal. Processing a
transaction can includes digital filtering, error detection, error correction,
, ~
21~30~
decryption and storage of the data. The second functlon is to determine the linenumber and field number of the video. The line and field numbers are used by
other components of the subscriber terminal, such as the descrambler control 110and the on-screen display control 132.
. .
The control and secure microprocessor interface 310 provides connection
between the registers for the VBI decoder 129 and control microprocessor 128 andsecure microprocessor 136. The control microprocessor 128 interfaces with the
f VBI decoder 129 to control operations thereof. The secure microprocessor 136
provides the VBI decoder 129 with information required to perform descrambling
and information recognition functions. For example, the secure microprocessor
126 may provide a present encryption seed, the next encryption seed, and the
subscriber terminal address.
Sync filter 320 removes noise spikes from the sync input signal. The sync
filter may be a running average circuit that averages the state of sync input signal
within a window that contains a predetermined number of samples. The output of
sync filter 320 is supplied to sync recognizer 330. If non-scrarnbled or restored
video is present, the sync recogDr 330 detects horizontal sync pulses, vertical
sync pulses and equalizing pulses, and determines the video line number and the
field from the output of sync filter 320. In addition, sync recognizer 330 outputs
a signal to decoder state machine 350 to indicate whether the video is either non~
scrambled or restored. Output signals are also supplied to the descrambler control
110 and the on-screen display control 132. The pu1se width modulator (PWM)
370 indicates the beginning of the horizontal sync pulse and other control pulses
to circuitry external of the MCC 104.
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The data filter 340 removes noise spikes from the VBI data signal and
outputs a filtered signal to decoder state machine 350 and digital phase locked loop
(DPLL) 360. DPLL 360 tracks the filtered VBI data and generates a "strobe"
signal at the center of each bit cell. The strobe signal is used to determine when
the VBI data should be sampled. The decoder state machine 350 performs the
processing of the VBI data. The memory interface 380 performs two functions.
First, it serves as the interface between the decoder state machine 350 and the
internal RAM. Second, it sends data to the memory controller 112, which stores
the data into an external DRAM 137.
The decoder state machine 350 identifies the VBI transactions from the
scrambler at the headend and processes the descrarnbler transactions and the
subscriber terminal transactions. In general, descrambler transactions can occur,
for example, on NTSC lines 9 through 21. Processing a transaction can include
error correction, decryption, cyclic redundancy code (CRC) computation and
storage into DRAM 137.
To detect a transaction, the decoder state machine loads the bits of the
transaction into a shift register. The filtered VBI data is coMected to the input of
a shift register. When the "strobe~ pulse from DPLL 360 goes high, the shift
register shifts its contents and latches the value at its input. If the DPLL 360 is
locked, the value at the input of the shift register will be a sample from the center
of a bit cell, not an undesirable sample from between two bit cells.
The detected serial bitstream may be stored temporarily in RAM before it
is written to the DRAM 137. This may be required if the memory controller 112
is servicing other modules, such as the on-screen display 132. The data is then
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s:
.
~ 21~730~ :
read from the RAM and sent to the memory controller 112 which writes the data
into DRAM 137. The decoder state machine 350 supplies the address, the data
from RAM and timing signals to the memory interface 112. Data transfers
between internal RAM and memory controller 112 are accomplished via memory
, 5 interface 380.
Subscriber terminal transactions (also called in-band VBI transactions) can
; appear, for example, on any line that does not contain a vertical sync pulse (e.g.,
any line except for lines 4, 5, and 6). After the decoder state machine 350 detects
. a descra nbler transaction, it waits until a place where the "pedestal" might be
present. Strobe pulses from the DPLL 360 latch the bits of the transaction into a
shift register.
At this time, the decoder state machine may determine from a recovered
control bit whether the transaction is addressed or global. If the transaction is
addressed, the decoder state machine 350 compares the subscriber taminal addressin the data to the subscriber terminal address stored in a register. If the addresses
do not match, the transaction is ignored. If there is a match, the received data is
decrypted and stored in the internal RAM. Finally, the decoder state machine 350reads the data from the RAM and sends it to the memory controller 112 which
writes the data into DRAM 137. The decoder state machine 350 supplies the
address, the data from RAM, and timing signals to the memory interface 112.
Data transfers between internal RAM and memory controller 112 are accomplished
via memory interface 380.
A brief description of the on-screen display will now be provided. As
noted above, the on-screen display is implemented from the on-screen display
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21~i30~
control 132. The screen may include for example 16 lines with either 45
characters per line, 24 characters per line, or a combination of both. The cubesused to display text can vary in size. ln a preferred embodiment, the size of the
cubes must conform to the following inequality:
~ ~;
(height x width)/2 5 256
In this case, there is a minimum of seven pixels and a maximum of thirty-two
pixels for the width of the cube. There is a minimum of six pixels and a
maximum of sixty-four pixels for the height of each cube. Underlining can be
activated and deactivated on a per-cube basis. The background display may take,
for example, any of 4096 different colors, including transparent. Characters or
graphics overlayed onto active video may be surrounded by a block of black
background to enable easy distinction from the video. Additional details of an on-
screen display control may be obtained from U.S. Patent Application Serial No
08/073,404, entitled "Msplay System for Subscriber Terminal", which is
incorporated herein by reference, and U.S. Patent Application Serial No.
07/800,836, entitled ~Method and Apparatus for Providing an On-Screen User
InterfaceforaSubscriptionTelevisionTerminaln, filedNovember29, 1991, which
is incorporated by reference.
Figures 4A-4C illustrate a feature of the present invention whereby a
plurality of multi-service virtual channels may be provided from a single 6 MHz
bandwidthphysical channel. In the illustrated example, multiple differentvirtualchannels can be defined from a composite video signal having one or more text
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2147~0~
streams multiplexed in the vertical blanking interval (VBI) thereof. For example,
three text streams may be multiplexed into the VBI of the composite video signalat the headend. The three text streams may correspond to, for example, local
weather forecasts, daily financial information such as Dow Jones averages and
stock prices, advertisements, and local news or events, among other possibilities.
The composite video signal may correspond to, for example, commercials, movie
or television previews, infomercials, or classified advertisements, among other
possibilities.
The subscriber terminal may provide for virlual chanslels as follows.
Memory, such as NVM, stores information sufficient to extract the programming
corresponding to each virtual channel from the broadband signal received from the
headend 12. For example, the NVM may store a mapping of virtual channel
numbers to one of the channels of the broadband television signal. In addition, the
memory may store a mapping of virtual channel number to particular information
transmitted in that channel. For example, this mapping may identify in the
channel a particu1ar data stream, a video signal, a audio signal, or a combination
thereof.
When the subscriber makes a selection, the control microprocessor 128
accesses the memory to obtain the information corresponding to the selected
channel. The control microprocessor 128 can then output control signals to ensure
that up/down converter 100 tunes to the appropriate channel and that the
appropriate information from the tuned channel is provided to the on-screen
display 132. For example, if the selected virtual channel corresponds to a
particular text data stream, the VBI data decoder is controlled to extract the text
-3 1 -
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data stream, ~erform any necessary processing, and supply the data to the on-
screen display control 132. Similarly, video and audio signals from the tuned
i channel may be processed and directed to the on-screen display control 132.
According to the present invention, virtual channels may be defined from
the information included in the composite video signal. Accordingly, multiple
services provided on the physical channel may be accessed using only a single
tuner. Figure 4A illustrates the display obtained from a virtual channel composed
of video #1 and text stream #3. Simultaneous display of the various services
corresponding to the defined virtual channel may be achieved using the overlay
feature of the on-screen display control 132. Forexample, the on-screen display
control 132 may overlay a selected one of the four video signals onto a selectedone of the text streams. In such a case, the selected video may form the
foreground and the selected text stream may form the background, or the reverse.In addition, the foreground and background may be divided by borders to frame
the different portions of the picture. Further details concerning on-screen display
control 132 operations that may be used to overlay of video and text the can be
obtained from U.S. Patent Application Serial No. 08/073,404, which is
incorporated herein by reference.
Figure 4B illustrates the display obtained from a virtual channel composed
of video #3 and te~ct #1. Figure 4C illustrates the display obtained from a virtual
channel composed of video #4 and text stream #2. Of course, Figures 4A-4C are
intended to serve as examples and should not be considered limiting.
Alternatively, two or more videos may be displayed simultaneously with text
and/or graphics, and any portion of the display may have text overlayed on it. In
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214730~
fact, the syslcrn operator may define any combinatioll of services on the selected
bandwidth for display as a separate virtual channel.
Furthermore, the system operator may authoriæ the subscriber to create a
desired multi-service display from the services available from a composite videosignal. For example, a menu page may be provided to assist the subscriber in
selecting video and text services from the composite video signal provided on a
physical channel. -
In addition, the subscriber may utilize two subscriber terminals coupled via
their data ports 140. The subscriber terminals may operate in a master-slave ;
relationship. Accordingly, the subscriber may further increase the viewing ehoices
available by selecting a picture-in-picture display whereby one subscriber terminal
tunes to one of the virtual channels defined from a composite video signal and the
. ~ .
other subscriber terminal tunes to either a second defined virtual channel, another
virtual channel, or a channel having a standard television signal. Alternatively,
the subscriber may view information displayed from one of the tuners and record -
on a VCR, for e~unple, information from the other subscriber terminal. -~
Accordingly, the subscriber is afforded an extremely wide range of combinations ~ ~
of programming from only two frequency channels. ~ ~ ;
The te~t channel, EPG, and messaging capabilities of the subscriber
television system will now bedescribed. Te~tchannels, EPG, and messages are
transmitted as data from the headend 12 to the subscriber terminal 14 in, for
e~ample, the vertical bhnking interval of the video portion, modulated on the
audio carria, or via outband transmission. A further understanding of the
techniques by which data may be transmitted can be obtained from U.S. Patent
. ,~
-33-
. ~.
~ 21~730~
Application ~erial No. 07/983,766, entitled "In-Band/Out-of-Band Data
Transmission Method and Apparatus for a Television System", which is
incorporated herein by reference. Accordingly, the subscriber can access a variety
of information that the system operator may offer, such as local news, sport
shorts, cable account status, help screens for assisting the subscriber in using the
subscriber terminal, and support of PPV capabilities, among other possibilities.Text channels are virtual channels that may be selected by the subscriber
like an ordinary channel, but are not associated with a real video channel of the
broadband television signal. As discussed above, a text channel represents text
data inserted into a television signal. When a text channel is selected, the
corresponding data is read in real time from the data stream and displayed on the
television display, for example, characters on a colored background. The data
stream may contain a bit that cont~ols whether or not the audio on that channel is
muted. Accordingly, the system operator can provide music, news, or some other
audio with text display.
In a preferred, yet nonetheless non-limiting embodiment, the text displayed
on the screen will change as determined by the received transactions. The cable
operator may control the rate at which the screen changes, for exarnple, by
controlling the data rate to the subscriber terminals or by other means.
Accordingly, the subscriber would not be required to enter a control command in
order to advance to the next page of text. Rather, the subscriber could view allof the pages of text simply by tuning to the appropriate virtual channel and waiting
for all of the pages to appear. Of course, the system may also be configured to ~ -
permit the user to control the advance of text pages.
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The sl.~scriber terminal is additionally capabl~ of receiving an EPG that
allows a subscriber to view a schedule of programming for the next several hours,
where the number of hours depends upon the memory installed. The information
is downloaded from the headend via transactions and is stored in memory. The
subscriber terminal may be tuned to the EPG data channels whenever possible
(e.g., when in "off mode," in certain menus, when the EPG is accessed) to keep
the EPG database loaded to the maximum level and to replace programs already
shown with new programs. Additional details of the EPG may be obtained from
U.S. Application Serial No. (Attorney Docket No. 1263.45792), enti~ed "Pay-Per~
~ . :
View Electronic Programming Guide", filed concurrently herewith and
~"- .~.
incorporated by reference.
As discussed above, messages are addressably or globally sent from the
- :- - , :
headend 12 to the subscriber terminal 14. In effect, the subscriber terminal 14
serves as a personal mailbox between the subscriber and the system operator. A
message is comprised of, for example, 16 screens having 16 lines of either 24 or45 charactcrs. For example, a maximum of 44 transactions would be required to
download each 45x16 screen. The message characters may be defined in the on-
screen display control character set. Further, the transmitted messages may use
control characters and word representations in addition to single characters to
increase information capacity and reduce memory requirements. Messages may
indexed by a predetermined number of bits. For example, if a 24-bit number is
used as an index, up to 16 million possible messages are enabled.
Preferably, messages are provided over one or more channels. The
.. ~ .
scrambler used transmit the messages is equipped with internal data RAM to store ~ ~
. ~ ~ :'' ,.,
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the message loop from the HEC so that the messages are retransmitted constantly
to ensure reception. The serial nature of the system is such that as messages are
added, the response time slows. However, the response time can be increased by
providing additional message channels and/or by using text compression.
S A subscriber terminal may be addressably assigned to any combination of
groups, for example, 128 groups. A message definition transaction, which is
preferably transmitted with all data streams, defines the display number for a
particular address or group, the background color, and where to tune for the
message. This information may be stored in the subscriber terminal RAM. When
the subscriber terminal receives a message definition transaction for any group to
which it belongs, the subscriber terminal will look for the message with the
corresponding display number or other identifier. Message data may be read
directly from the data stream or may be stored, in whole or in part, in memory,
for example in RAM. Messages that have not been read may be given a higher
lS priority than messages that have been read. Accordingly, if memory is limited,
néwly received messages may overwrite messages that have already been read out
of memory. An LED on the front panel of the subscriber terminal and/or the
display of a te~ct message may indicate whether a new message has been received.Figures 5A and 5B illustrate the menu screen used in connection with the
message processes. The main menu screen 510 offers the subscriber a number of
possible selections. A subscriber may read a message by, for e~ample, selecting
the "Messages/Information" option from the menu. If no messages have been
reseived, screen 520 is displayed to indicate this status to the subscriber. If a
message has been received, a screen 540 is provided to exhibit the various
. :':~.
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214 7391
categories o~ messages available. Alternatively or m addition, a screen 530,
indicating that a message has been received, may be overlaid on active video of
program being viewed. By entering a "menu" key on the remote control or
keyboard, a user may enter the screen 540.
Display 540 enables the subscriber to select from any of a number of
message categories. The message categories may be used to associate message
. - .
types and clas,sifications with specific messages. The message categories are
globally downloaded via global transactions and stored in volatile RAM. As
illustrated further below, the message categories are built in a tree-like structure
of categories so that a message may be found by searching specific lower
categories. The subscriber is notified that a particular message category contains
, a message by, for example, use of an asterisk next to the appropriate category.
Of course, another indicator may be used consistent with the present invention.
If the subscriber selects a category from screen 540, either the message is
displayed as illustrated by screen S90 or second level categories are displayed by
screen SS0. In the example of Figure SA, when "Sports" is selected from screen ~ -~
:,
540, a screen SS0 displays the various subcategories of "Sports" category, namely
"BasebaU", "Football", "Horse Racingn, "Bowlingn, "Fencing" and "Chessn. It
should be clear that the subcategories listed are intended to be illustrative, and -~
.............. ...................................................................................... ........... ... ~
should not limitthe invention. ~ ~ `
When a subcategory is selected from screen SS0, eitha a message is
displayed as shown by screen 590 or third level categories are displayed as shown
by screen 560. The subscriber terminal 14 is capable of supporting fourth level
categories as illustrated by screen 570, or further subcategories. If a message has
. - . ....
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not yet been stored in memory, subscriber terminal 14 may display screen 580 to
indicate to the subscriber that the message is in the process of being received.The subscriber system and subscriber terminal described herein may be
adapted to support digital television signals and compressed digital television
signals, e.g. MPEG signals, æ should be clear to those skilled in the art. When
compressed digital television signal are utilized, bandwidth is available for carrying
additional audio and/or data streams to thereby increase the number of options the
present invention provides. --
Although illustrative embodiments of the present invention have been
described in detail with reference to the accompanying drawings, it is to be
understood that the invention is not limited to those precise embodiments and that
changes and modifications may be effected therein by those in the art without
departing from the scope and spirit of the invention.
" '
:. .
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