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Description  |
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FIELD OF THE INVENTION
The invention pertains 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.
BACKGROUND OF THE INVENTION
Subscription television systems can be cable television systems (CATV), multi-point, multi-distribution subscription systems (MMDS), direct-to-home (DTH) broadcast 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 programming 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. Further, they provide conditional access to particular subscription service through authorization of
particular channels of service by descrambling.
More recently, the subscriber terminal 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 terminal with advanced consumer features is the Model 8600 series of subscriber terminals manufactured by Scientific-Atlanta, Inc. of Norcross, Ga. These terminals generally provide on-screen displays by
combining the video signal from a selected channel with an on-screen display video signal from a video generator prior to remodulation of the 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 Ser. No. 08/073,404, filed Jun. 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 additional 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
transmitted via a distribution system to subscriber terminals. Each of the 6 MHz frequency channels includes video and audio information corresponding to a discrete television (TV) program. Accordingly, to transmit four TV programs, for example, 24 MHz
of bandwidth is required. When the user selects a service channel for viewing, the subscriber terminal tunes to the corresponding frequency channel, and video and audio information associated with the selected service channel is displayed.
Multi-service communications systems transmit different services over one 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 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 text services and the TV service provided on that frequency channel.
U.S. Pat. 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-channel map, and a channel
configuration map. The service definition table defines the relation 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. Pat. 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 combination of 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.
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 other information connection. The incoming cable carrying the broadband television signal is input to an RF splitter
having outputs to each of the master and slave subscriber terminals. All control functions can be performed by the master subscriber terminal. For example, the master subscriber terminal may be used to 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 output of one of the subscriber terminals to the recording device.
However, it is expensive for each subscriber to purchase or lease two subscriber terminals. 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.
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-service channels, including 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 or more 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-friendly and that is capable of supporting additional features.
It is a further object of the present invention to provide a subscriber terminal for receiving multi-service channels, including video and text services, and enabling display of a combination of services simultaneously.
It is a further object of the invention to provide a subscriber terminal for receiving a channel of service, including a composite of a several video services and one or more text 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 multiple channels of information via a distribution system to at least one subscriber terminal
remote from the 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 carded as amplitude modulation of the sound carder of the composite video signal.
The composite video signal is then modulated onto a channel of the broadband television signal which is transmitted to the subscriber terminal. Moreover, additional information, for example text data streams, may be transmitted over a dedicated
out-of-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 virtual 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 the
tuner. 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 program determined from the video program control signals.
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 signal such that
one of the four programs appears in one quadrant of the displayed picture and text information 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 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 streams. For example, the composite video signal may be formed from video signals of four different video programs. The composite video signal is formatted such that the four video programs would
appear without distortion in a respective quadrant of the television display. The text 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 channel to the channel of the broadband television signal that the composite video signal occupies. In addition, the memory stores a mapping of the virtual channel to a
combination of a text data stream and a portion 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 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 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 signal corresponding 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.
BRIEF
DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the invention becomes better understood by reference to the following detailed description when considered in
connection with the accompanying drawings.
FIG. 1A is a detailed diagram of a subscription television system according to the present invention.
FIG. 1B illustrates an embodiment of a video combiner according to the present invention.
FIG. 1C provides a representation of a display of the composite video signal output from the video combiner illustrated in FIG. 1B.
FIG. 2 is a detailed black diagram of one of the subscriber terminals shown in FIG. 1A.
FIG. 3 illustrates an embodiment of the VBI data decoder shown in FIG. 2.
FIG. 4A illustrates the display obtained from a virtual channel composed of video #1 and text stream #3.
FIG. 4B illustrates the display obtained from a virtual channel composed of video #3 and text #1.
FIG. 4C illustrates the display obtained from a virtual channel composed of video #4 and text stream #2.
FIG 5A-5B illustrate the menu screen used in connection with the message processes.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1A is a detailed diagram of a subscription television system according to the instant invention. The system of FIG. 1A is intended to serve as 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 as headend 12. Headend 12
provides a subscription television service to a local area, for example, 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 example, 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 "HEC") 28 of the headend 12. HEC 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 or out-of-band 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 IPPV processor 34. 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, optical 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 ("ISP") 42 may also receive text data for transmission to subscribers. The text data may include weather information,
sports scores, messages, etc. and may be provided by an information service 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 data may depend on the amount of data to be transmitted, the number of channels on which the data is to be
transmitted, and the frequency at which one wishes to supply the data to the subscriber terminal. The two scramblers 44 and 46 in FIG. 2 are for example only. Scramblers 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 example 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 carder 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 Ser. No. 07/983,766, entitled "In-Band/Out-of-Band Data
Transmission Method and Apparatus for a Television System", incorporated herein by reference, U.S. patent application Ser. No. 07/799,987, entitled "Method and Apparatus for Message Information", filed Nov. 29, 1991, which is incorporated by
reference, and U.S. patent application Ser. No. 07/800,241, entitled "Method and Apparatus for Tuning Channels in a Subscription Television System having In-Band Data", filed Nov. 29, 1991, which is incorporated by reference. Also, further
information concerning EPG and pay-per-view processing can be obtained from U.S. patent application Ser. No. 08/230,144, entitled "Pay-Per-View Electronic Programming Guide", filed Apr. 19, 1994 and incorporated by reference.
The EPG data received by satellite receiver 40 will often be very extensive, containing data for programs 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 amount of memory which would greatly increase terminal costs. Thus, ISP 42 can select 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 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 covered 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) than long
term data. For this purpose, scramblers 44, 46 are provided dynamic random access memory (DRAM), 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 service provider, such as a stock quote service, or generate text data locally. The text data may received via satellite, dial up modem, direct connect modem, direct
connect to system manager, or other known means. The text data may either be transmitted as received or reformatted by ISP 42, then transmitted to a scrambler (44 or 46) for transmission to subscribers as described above.
ISP 42 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 received
via satellite receiver 40, as shown, or by other means such as local 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 FIGS. 1B and 1C. 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 scramblers. 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 example, 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 descrambling information does not mean that each
subscriber terminal can descramble the received signal. Rather, only authorized subscriber terminals would actually be capable of descrambling a received signal.
On the other hand, data transmissions may be addressed transmissions. Authorization data would normally be addressed to individual subscribers or groups 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 FIG. 1A, for example only, one subscriber terminal is shown. Typically, at given location only one terminal will be found. However, two terminals may be provided FIG. 1A 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 FIG. 1B, 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 invention. Video combiner 64 reformats 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 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.
FIG. 1C provides a representation of a display of the composite video signal discussed above. As shown in FIG. 1C, 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 subscriber terminals utilizing only 6 MHz of bandwidth. However, the composite video signal
transmitted 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 forms, 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 FIG. 2, a detailed block diagram of one of the subscriber terminals 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 example, multiple tuners (not shown) may be provided for tuning to more than one television 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 audio data when used by the subscriber 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 predetermined 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 an 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 or predetermined default RF channel signal to a 45.75 MHz intermediate frequency signal. A multifunction control circuit (MCC) 104 is linked to up/down converter by 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, for example a microprocessor.
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 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 blanking interval or via out-of-band 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 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 buffering. Descrambler 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. Pat. 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.
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 well 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 will be discussed in connection with FIG. 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 and/or graphics. The modulator 142 combines the video 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 frequency selected 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 the microprocessor 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. These subscriber 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 LED display, 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 execute 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 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 descrambling data to generate appropriate control signals, for example, inversion control and equalizing, sync restoration or regeneration for descrambling, or otherwise restoring 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 form of descrambling is required at a particular time by interpreting
the authorization and control 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 internal non-volatile memory (NVM) of the device. The NVM in
the secure microprocessor 136 stores secure data, for example, authorization data, scrambled channel dam, some terminal configuration data and other required data.
The control processor 128 operates by running a control program which preferably is partially stored in a read-only memory internal to the processor and partially 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 Ser. No. 07/983,909, entitled "Reprogrammable Subscriber
Terminal", filed Dec. 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 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
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 h | | |
