Patent Publication Number: US-8528013-B2

Title: Method and apparatus for limiting access to programming in a switched digital video system

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to content delivery systems that deliver broadcast channels and switched digital video (SDV) channels to subscribers and to parental controls for limiting access to content in such systems. 
     BACKGROUND OF THE INVENTION 
     The exposure of children to inappropriate material on television, such as sexual content, violence, coarse language, and so forth, has long been a concern. Recent technological developments now allow parents and other responsible individuals to control what children may see on television and to view a log of programming that has been previously viewed. For example, access to programming may be controlled by a user (e.g. a parent) based on certain program characteristics, such as program titles, ratings, times, or channels. In such systems, programming may be blocked and unblocked by entering a parental control code in a set top terminal through which the programming is received. This can be a cumbersome process, especially if the user desires to block channels on a room-by-room basis in residences where there are multiple televisions each with their own set top terminal. In this case each set top terminal needs to be separately programmed to prevent or limit access to certain program content. 
     Accordingly, it would be desirable to provide a simplified arrangement for limiting access to programming and for acquiring a log of previously viewed programming which is easy for the end user to configure, regardless of the number of set top terminals that may be present in the residence. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows one example of a content delivery system  FIG. 2  shows one example of the headend depicted in  FIG. 1 . 
         FIG. 3  shows one example of a setup menu that may be displayed to the user when contacting the headend. 
         FIG. 4  shows a first parental control interface screen that may be presented to the user if the user has more than one set top terminal in his or residence. 
         FIG. 5  shows a channel lock interface screen that may be presented to user after making a selection from the parental control setup option in  FIG. 3  or a selection from the screen  FIG. 4 . 
         FIG. 6  shows a content rating interface screen that may be selected by the user. 
         FIG. 7  shows another example of a parental control interface screen that may be presented to the user after selecting the parental control setup option in  FIG. 3 . 
         FIG. 8  shows a parental control interface screen that may be presented to the user after selecting the account for “Tommy,” in the screen shown in  FIG. 8 . 
         FIG. 9  shows a purchase control criteria display screen that may be presented to the user after selecting the purchase control option from the screen shown in  FIG. 8 . 
         FIG. 10  shows the logical architecture of one particular example of a set top terminal. 
         FIG. 11  shows one example of the hardware employed in the set top terminal of  FIG. 10 . 
         FIG. 12  is a flowchart showing one example of a method by which an SDV system ensures that only programming conforming to subscriber-established rules is provided to the subscriber. 
     
    
    
     SUMMARY 
     In accordance with one aspect of the present invention, a content delivery system headend is provided. The headend includes a Switched Digital Video (SDV) manager for coordinating SDV sessions requested by subscribers over an access network. The headend also includes an input unit such as a server for receiving content to be broadcast during the SDV sessions. Additionally, the headend includes a subscriber control unit for comparing channel change requests received by the SDV manager from subscribers to subscriber-established rules. Tuning information for accessing programming specified in the channel change requests is only supplied if the channel change requests do not conform to any of the subscriber-established rules for blocking the programming. 
     In accordance with another aspect of the invention, a method is provided for accessing programming over an SDV system. The programming may be accessed by a subscriber terminal such as a set top terminal. At least one rule for blocking programming is provided to the SDV system. In response to user input, a channel change request is sent. The channel change request requests the SDV system to supply a selected program or channel. A control message is received in response to the channel change request. The control message includes tuning information for tuning to a program or channel different from the selected program or channel if the selected channel or program does not conform to the rule. The subscriber terminal tunes to the different program or channel as directed by the control message. 
     DETAILED DESCRIPTION 
     As detailed below, parental controls can be implemented in a relatively simple manner in Switched Digital Video (SDV) systems. SDV refers to an arrangement in which broadcast channels are only switched onto the network when they are requested by one or more subscribers, thereby allowing system operators to save bandwidth over their distribution network. In conventional cable or satellite broadcast systems, every broadcast channel is always available to all authorized subscribers. In contrast, a switched digital video channel is only available when requested by one or more authorized subscribers. Also, unlike video on-demand, which switches a singlecast interactive program to a user, switched digital video switches broadcast streams, making each stream available to one or more subscribers who simply join the broadcast stream just as they would with normal broadcast services. That is, once a switched service is streamed to a subscriber, subsequent subscribers associated with the same service group as the first subscriber can tune to the same broadcast stream. The switched digital video will often share the same resource managers and underlying resources with other on-demand services. 
     SDV systems can simplify implementation of parental controls because each time a user changes from one channel to another, a channel change request is sent from the user&#39;s subscriber device (e.g., a set top terminal) to a session manager in the network&#39;s headend. Channel change requests are one type of message that is communicated between the session manager and the subscriber using an SDV Channel Change Message (CCM) protocol, which can be implemented as a proprietary protocol or as an open standard. After a channel change request is passed from the subscriber to the session manager, the session manager would normally respond by sending a message that requests the subscriber device to tune to a channel on which the SDV channel will be made available. The message also includes the necessary tuning information for tuning to that SDV channel. In the present case such additional messages will direct the subscriber device to tune to an alternative channel, typically a channel that presents a message to the subscriber that the desired channel is being blocked. That is, the correct tuning information for the desired channel will be sent from the session manager to the subscriber device only if the channel change request conforms to pre-established rules (e.g., parental controls) that the user has made available to the session manager. 
       FIG. 1  shows one example of a content delivery system architecture  100  for delivering both broadcast channels and switched digital channels to a subscriber during a switched digital video (SDV) session. The SDV session is implemented through a service offering in which application level data generated by a set-top terminal initiates a SDV session request and an SDV manager routes data in accordance with the request to provision the service. Among other components, system architecture  100  comprises a content distribution source such as a headend  110  that is connected to multiple intermediate entities such as hubs  130 ,  132  and  134 . The headend  110  communicates with a switch or router  170  in hubs  130 ,  132  and  134  over links L 1 , L 2  and L 3 , respectively. The headend  110  and hubs  130 ,  132 , and  134  may communicate over a packet-switched network such as a cable data network, passive optical network (PON) or the like using, for example, IP multicast addressing. 
     Some or even all of the hubs are connected to multiple users, typically via distribution networks such as local cable access networks (e.g., HFC networks). For simplicity of explanation only, each hub is shown as being connected to a distinct HFC network, which in turn communicates with end user equipment as illustrated. In particular hubs  130 ,  132  and  134  in  FIG. 1  communicate with access networks  140 ,  142  and  144 , respectively. Each access network  140 ,  142  and  144  in turn communicates with multiple end user devices such as set top or subscriber terminals. In the example of  FIG. 1 , access network  140  communicates with set top terminals  120   1 ,  120   2 ,  120   3 ,  120   4  and  120   5 , access network  142  communicates with set top terminals  122   1 ,  122   2 ,  122   3  and  124   4 , and access network  144  communicates with set top terminals  124   1 ,  124   2  and  124   3 . 
     In addition to the switch or router  170 , each hub can include an array of radio frequency transmitter edge devices such as edge QAM modulators  150 . The number of edge devices  150  in each hub may vary as needs dictate. For instance, as previously noted, the number of edge devices needed to implement SDV channels is generally much greater than the number of edge devices needed to implement broadcast channels. As used herein, the term “QAM” refers to modulation schemes used for sending signals over cable access networks. Such modulation schemes might use any constellation level (e.g. QAM-16, QAM-64, QAM-256 etc.) depending on the details of a cable access network. A QAM may also refer to a physical channel modulated according to such schemes. Typically, a single QAM modulator can output a multiplex of ten or twelve programs, although the actual number will be dictated by a number of factors, including the communication standard that is employed. The edge QAM modulators usually are adapted to: (i) receive Ethernet frames that encapsulate the transport packets, (ii) de-capsulate these frames and remove network jitter, and (iii) transmit radio frequency signals representative of the transport stream packets to end users, over the HFC network. Each transport stream is mapped to a downstream QAM channel. Each QAM channel has a carrier frequency that differs from the carrier frequency of the other channels. The transport streams are mapped according to a channel plan designed by the MSO that operates the network. 
     Each hub  130 ,  132  and  134  also includes an edge resource manager  160  for allocating and managing the resources of the edge devices  150 . The edge resource manager  160  communicates with and receives instructions from the session manager located in the headend  110 . In some cases the edge resource manager and/or session manager can be located in the headend. 
       FIG. 2  shows one example of headend  110 . The headend  110  includes a broadcast content source  210 , which may include, by way of example, satellite receivers, off-air receivers and/or content storage devices such as servers. A SDV manager  215  is used to determine which SDV transport streams are being transmitted at any time and for directing the set top terminals to the appropriate stream. The SDV manager  215  also keeps track of which subscribers are watching which channels and it communicates with the edge resource managers  160  in the hubs so that the content can be switched on and off under the control of the SDV manager  215 . In addition, all subscriber requests for a switched digital channel go through the SDV manager  215 . The switched digital channels are forwarded to a rate clamp  220  and one or more encryptors  225  using, for example, IP multicast addressing. The content is then encrypted by the encryptors  225  and transmitted to the appropriate hub or hubs. Typically, standard definition (SD) channels are currently rate clamped to 3.75 Mbps while high definition channels are currently rate clamped to between about 12 Mbps and 15 Mbps. The encryptors  225  encrypt the digitally encoded content, often under the control of a conditional access system (not shown). 
     Headend  110  may also include a network DVR  240 . The network DVR  240  stores content that can be transmitted to set top terminal via a hub and access network in response to a user request to play a program stored on the DVR  240 . Other user input requests are also serviced by network DVR  240 , including, for example, requests to accelerate the playing of a program in the forward direction (e.g., cueing) and in the reverse direction (e.g., reviewing). The content is stored by the network DVR  240  upon a user request. The content may be provided to the network DVR  240  from any available content source, including, for example, content source  210 . 
     It should be noted that in some cases the functionality of some or all of the SDV manager  215  may be transferred to each of the hubs  130 ,  132  and  134 . For example, as described below, Channel Change Messages may be communicated between the set top terminals and the hubs. In addition, some or all of the functionality of the SDV manager  215  may be distributed among other components such as an SDV operations manager (SDVOM), which is sometimes used to configure and monitor SDV systems. 
     Headend  110  may also include a variety of other components for offering additional services. For example, in  FIG. 2  a video on demand (VOD) server  230  is shown for storing programs or other content for distribution to subscribers on an on-demand basis. Although not shown, one of ordinary skill in the art would recognize that other components and arrangements for achieving the various functionalities of headend  110  are possible. For example, the head-end  110  may comprise typical head-end components and services including a billing module, an advertising insertion module, a subscriber management system (SMS), a conditional access system and a LAN(s) for placing the various components in data communication with one another. Headend  110  also includes a parental control server  218 , which will be discussed below. It will also be appreciated that the headend configuration depicted in  FIG. 2  is a high-level, conceptual architecture and that each network may have multiple head-ends deployed using different architectures. 
     The edge devices  150  provide programming to the set top terminals using the downstream in-band channels. To communicate control information and the like with the headend  110  and/or the relevant hub, the set top terminals may use out-of-band (OOB) or DOCSIS channels or an IP tunnel or an IP connection and associated protocols. However, in some cases communication of control information and the like can be performed using in-band channels as well. 
     Control information that may be communicated over the out-of-band channels includes the aforementioned SDV channel change messages (CCM), which are used to pass channel change requests from the subscriber to the SDV manager  215  in the headend  110 . In particular, the SDV manager  215  receives channel change requests for switched digital content from a set top terminal to bind that content to a session on one of edge devices  150  serving that set top terminal&#39;s service group. The channel change request message is generated by the SDV application (or its designated proxy) resident in the set top terminal in response to the subscriber&#39;s program channel request that is entered by the set top terminal&#39;s user interface. The SDV manager  215  responds to the set top terminal with the frequency and program number where that content may be found. The SDV manager  215  requests the set top terminal to tune to the channel corresponding to this frequency and program number using a so-called force tune function. The SDV manager  215  also receives channel change request messages for non-SDV (e.g., broadcast) channels in order to gather statistics that can be used to better understand subscriber activity and to provide information that can be used for targeted advertising and the like. Another reason to receive non-SDV channel changes is so that the SDV Manager knows when the set top terminals are no longer tuned to an SDV channel, thus allowing the SDV Manager to remove the SDV channel from the network to save bandwidth. 
     As previously mentioned, since the SDV manager  215  receives channel change requests for SVD and non-SDV channels, the SDV manager can be configured so that the necessary tuning information is only passed along to the subscriber in an in-band or out-of-band control message if the channel change request conforms to pre-established rules (e.g., parental controls) that the user has made available to the session manager. If the request does not conform to the pre-established rules, the control message from the SDV manager will direct the subscriber to tune to an alternative channel, typically a channel that presents a message to the subscriber that the desired channel is being blocked. In some cases it may be necessary to prevent the set top terminal from acquiring the tuning information for the blocked program or channel for an alternative source such as the active services list that is often transmitted using the min-carousel protocol (MCP). This can be accomplished by sending a control message to the set top terminal instructing it to only tune to channels provided through the SDV manager. 
     The pre-established rules may be communicated to the SDV manager  215  in any appropriate manner. For instance, in one example, the user may supply the rules via an Internet-enabled client device that accesses a user account database in a server associated with or in communication with the SDV manager  215 , such as parental control unit or server  218  depicted in  FIG. 2 . The client device may be the user&#39;s own set top terminal or another device such as a personal computer, PDA, networked appliance, cellphone or the like. The user account database may be accessed through an application-level interface residing on the client device such as a web-browser. 
       FIG. 3  shows one example of a setup menu  102  that may be displayed to the user when contacting the headend  110 . The menu presents various settings options such as an advertising setting  107 , reminder setting  109 , parental control setup menu  104  as well as a viewing log  105 . The parental lock feature may be accessed by selecting the parental control setup menu  104  so that a parental control interface is displayed, examples of which are shown in  FIGS. 5-9 . In some cases an input dialog box will first appear requiring a password to be input prior to accessing the parental lock interface. In other cases a password may not be required until an attempt is made to alter the control settings.  FIG. 3  also shows a viewing log option  105  that allows the subscriber to see a list of all the programming that has been viewed through the various set top terminals in the household over some selected period of time (e.g., the past week). Information in the log can be used, for example, to revise and refine the parental controls that are put in place by the subscriber. 
     The parental control interface screen  103  of  FIG. 4  may be presented to the user if the user has more than one set top terminal in his or residence. This screen  103  provides the user with a pulldown menu  111  that presents the user with the option to establish a common set of controls for all the set top terminals or to establish different sets of controls on a room by room basis. Once the desired selection has been made, the channel lock interface screen  223  shown in  FIG. 5  may be presented. The interface screen  223  presents a channel lock button  224 , which is highlighted (or otherwise made visually distinguishable) in  FIG. 5  to indicate that it is the selected screen. The interface screen  223  includes a field  230  of channel cells  232 . In each channel cell there is a channel identifying field  234  and a channel number field  236 . The channel identifying field contains channel identifying indicia such as one or more of the channel number, channel call letters, channel name, and the like. In other examples, the channel logo may be depicted in the channel identifying field, for example, as each channel cell&#39;s sole channel identifying indicium, or, in addition to one or more of channel number, channel call letters, channel name, and so forth. 
     In the channel lock interface screen  223 , a user may select particular channels to lock and unlock, for example, wherein clicking on a particular channel cell toggles that channel between a locked and unlocked state. The indicia within the cells of locked channels generally will be distinguishable from unlocked channels. In the event that the number of channels available is greater than the number of channel cells  232  that may be displayed within the interface screen  223 , a scroll bar  238  may be provided to allow a user to bring additional channels into view in field  230 . A button  244  is provided to turn on parental locks after a user&#39;s selections have been made using the channels cells  232 . A lock all button  246  may be provided for locking all channels as well as an unlock all button  248  for removing all locks. A user&#39;s previous settings may be saved in memory and an undo button  250  may be provided that allows a user to discard any changes made and to reinstate earlier settings. If a password was not required to access the parental lock interface itself, a dialog box requiring entry of a password may be provided when the user selects one of buttons  244 ,  246 ,  248  or  250 . 
     If the user selects content rating lock button  226  in  FIG. 5 , the content rating interface screen  222  shown in  FIG. 6  may be presented. The interface screen  222  presents a field  240  of rating cells  242 . Each rating contains a TV or movie rating and a brief description of the rating. In the content rating interface screen  222 , a user may select particular ratings to lock and unlock. In one embodiment, clicking on a particular rating cell toggles that rating between a locked and unlocked state. The indicia within the cells of locked ratings generally will be distinguishable from unlocked ratings. Since the number of ratings available may be greater than the number of rating cells  242  that may be displayed clearly within the interface screen  222 , a scroll bar  238  may be provided to allow a user to bring additional rating cells into interface screen  222 . Content ratings interface screen  222  also include buttons  244 ,  246 ,  248  and  250  that operate in a similar manner to that described above in connection with  FIG. 5 . 
     When content is blocked either by channel or by content rating, the restriction may be applied completely or only for certain times of the day or week. Stated differently, content that is allowed to be viewed may be limited to a selected total aggregate viewing time (e.g., 2 hours a day) or it may be limited to certain times of the day or week (e.g., the Disney Channel can be viewed only on Saturdays between 4 and 7 pm). 
     In the examples described above either channel cells ( FIG. 5 ) or content rating cells ( FIG. 6 ) may be selected directly from the interface by a user. In other examples, however, a more interactive interface and method for obtaining input from a user may be employed. For instance, some users may prefer an interface which is even simpler and more automated. In this case a human oriented set of questions may be provided that asks about the individuals who will use the system and their ages. Questions may also be asked about the level of locking desired in general terms. In some cases the questions can be posed in an interactive or wizard format wherein a series of questions are asked and wherein the answers to the questions dictate the subsequent questions. For example, such a questionnaire or wizard interface might begin by asking if any of the users of the SDV system are children. If all of the users are adults, the program might then simply recommend that all programming remain unlocked. On the other hand, if the user indicates that a child or children will be viewing programming, the wizard may then query as to the children&#39;s ages. After the children&#39;s ages are entered by the user, the wizard may then recommend locking all programming which correspond to the age of the youngest child. For, example, if a user indicates that there are children under the age of 13, the user interface could then suggest that all programs rated for audiences 13 and older be locked. The lock would then be applied on all MPAA levels PG-13 and higher and lock all programs with a rating of TV-14 and higher. Instead of a questionnaire, the subscriber may be presented with a series pre-defined filters from which to select. For instance, some filters may be age-appropriate filters that only allow content suitable for selected age levels, while other filters may branded so that their name indicates something about the content that the filter will allow. For instance, a branded filter may be entitled “Clifford&#39;s Choices,” or “Oprah&#39;s Recommendations.” 
     Some users may prefer to establish parental control rules in an even simpler and more interactive manner than can be accomplished using the preceding interactive wizard interface. For these users the service provider may provide telephone support in which an operator obtains the input from the user and enters it on his or her behalf. In this way the user never even needs to directly input any information through a set top terminal, PC or other client device. 
     In addition to locking selected channels or programming, the predefined rules supplied by the user which are to be invoked by the SDV manager may impose a variety of other controls. For instance,  FIG. 7  shows another example of a parental control interface that may be presented to the user after selecting the parental control setup menu  104  in  FIG. 3 . In this example the user is provided with an opportunity to setup multiple accounts, one for each individual in the household. In particular, interface screen  170  includes multiple account control option  172 , add an account option  176  for adding new accounts and account listings region  174  for displaying information related to existing accounts. Account listings region  174  may include individual user-selectable accounts that may be identified by names and/or account types and the like. If, for instance, the user selects the account “Tommy,” the screen  131  shown in  FIG. 8  may be displayed, which includes a parental control option  135  and a purchase control option  143 . The parental control option  135  can be used to control channels or content ratings such as described above in connection with  FIGS. 5-6 . On the other hand, purchase control option  143  may provide the user an opportunity to set purchase control criteria for the selected account by presenting an interface screen such as the purchase control criteria display screen  133  shown in  FIG. 9 . As shown, examples of purchase control criteria include a total spending limit over a fixed period of time (e.g., day, week or month) and a delineation of the various products that may or may not be purchased such as pay per view programming, merchandise and/or premium services such as access to premium channels. 
     In operation, the SDV system will implement the rules that have been established by the subscribers each and every time the SDV manager  215  in  FIG. 2  receives a channel change request by accessing the user account database located in the server  218 . This can be accomplished by comparing the content of the channel change request to the rules located in the subscriber&#39;s account in the parental control database associated with server  218 . If the channel request matches one of the rules, the request to supply the SDV program will be denied. That is, the SDV manager  215  will not provide the subscriber with the necessary tuning information for the SDV program if such a match is found. Rather a message will direct the subscriber device to tune to an alternative channel, typically a channel that presents a message to the subscriber that the desired channel is being blocked. The message that is presented to the subscriber may indicate that the desired program is being blocked. The message may be a default message supplied by the service provider, or alternatively, the message may be customized by the subscriber. For instance, if a channel is blocked after expiration of a time period in Tommy&#39;s account described above in connection with  FIG. 9 , a message may be presented stating “Sorry Tommy, you&#39;ve watched TV for two hours now, time to read a book.” Of course, a wide variety of other customized messages may be presented depending on the particular rule that is invoked to block the channel or program. The customized messages may be input by the subscriber using, for example, the control interfaces described above. For instance, in  FIGS. 5 and 6 , each channel or content rating cell may have an option allowing the subscriber to provide a message that is to appear whenever the rule associated with that cell is invoked. 
       FIG. 10  shows the logical architecture of one particular example of a set top terminal such as those depicted in  FIG. 1 . In this example the set-top terminal is compliant with the OpenCable Application Platform (OCAP) hardware and software environment. The OCAP specification is a middleware software layer specification intended to enable the developers of interactive television services and applications to design such products so that they will run successfully on any cable television system, independent of set-top or television receiver hardware or operating system software choices. As is well known, middleware generally comprises one or more layers of software which are positioned “between” application programs and the lower or physical layers of the network device. Middleware is commonly written for the specific requirements of the operator of the computer system, and the proprietary software purchased by the operator of the computer system. A key role of middleware is to insulate the application programs from the device specific details. By using middleware the application programmers need know very little about the actual network details, since they can rely on the middleware to address the complexities of interfacing with the network. Of course, the set top terminal is not limited to an OCAP-compliant software/hardware architecture. In other cases, for example, the set top terminal may be compliant with MHEG, DASE or Multimedia Home Platform (MHP) middleware. Alternatively, the set top terminal may be based on a proprietary architecture. 
     Referring to  FIG. 10 , the top of an OCAP software “stack” includes a Monitor Application  300 , Electronic Program Guide (EPG)  302 , SDV application  304 , and any other applications  306  that may be deployed in a particular network. These applications are run on top of a software layer called the “Execution Engine”  312  and interface to the Execution Engine using the well known OCAP APIs  308 . The client device may also include certain software applications or “Native Applications”  318  that do not run within the Execution Engine, but directly run on top of the Operating System/Middleware  314  for the client device. Native Applications are typically written for, e.g., a particular hardware configuration  316  of the set top terminal. Examples of such Native Applications may include management of front panel functionality, remote control interaction, games, and the like. The objects downloaded to the client device in accordance with the techniques described herein may include any of the aforementioned applications and programs as well as additional applications, programs or other objects. However, during an upgrade many of the objects that need to downloaded may be directed to applications located above the OCAP application programming interface  308 . 
     When acquiring viewership information in accordance with the techniques described herein, the SDV application  304  is loaded onto the set top terminals. Once installed, the set top terminals can be readily configured to generate and transmit to the SDV manager the channel change requests, even if all the channels in the system are in a broadcast configuration. 
       FIG. 11  shows one example of the set top terminal hardware  416 . The device hardware  416  generally includes an RF front end  402  (including a modulator/demodulator and a tuner or tuners) for interfacing with the distribution network (e.g., HFC network  140 ) of  FIG. 1 , digital processor(s)  404 , storage device  406 , and a plurality of interfaces  408  (e.g., video/audio interfaces, IEEE-1394 “Firewire”, USB, serial/parallel ports, etc.) for establishing communication with other end-user devices such as televisions, personal electronics, computers, WiFi or other network hubs/routers, etc. Other components which may be utilized within the device include one or more decoder stages, various processing layers (e.g., DOCSIS MAC, OOB channels, MPEG, etc.) as well as media processors and other specialized SoC or ASIC devices. These additional components and functionality are well known to those of ordinary skill in the art and accordingly are not described further herein. 
     As noted, the SDV application  304  is responsible for communicating the channel change information (e.g., SDV CCMs) between the set top terminal and the SDV manager. The SDV application  304  also receives from the SDV manager the control messages that request the set top terminal to tune to a particular channel or program corresponding to the tuning information provided in the control message. 
       FIG. 12  is a flowchart showing one example of a method by which an SDV system ensures that only programming conforming to subscriber-established rules is provided to the subscriber. The method begins in step  505  when the SDV manager or other suitable entity in the SDV system receives a channel change request for a particular channel or program from the subscriber. Next, in step  510 , the SDV system compares the request to any rules that have been established by the subscriber for blocking a program or channel. At decision step  515 , the SDV manager determines if the requested program or channel matches any of the subscriber-established rules. If so, then at step  520  the SDV system supplies tuning information for an alternative program or channel which indicates that the requested channel or program has been blocked. If not, then at step  525  the SDV system supplies the tuning information for the requested program or channel to the subscriber&#39;s set top terminal so that the subscriber may view the requested program or channel. 
     The processes described above, including but not limited to those presented in connection with  FIG. 12 , may be implemented in general, multi-purpose or single purpose processors. Such a processor will execute instructions, either at the assembly, compiled or machine-level, to perform that process. Those instructions can be written by one of ordinary skill in the art following the description of presented above and stored or transmitted on a computer readable medium. The instructions may also be created using source code or any other known computer-aided design tool. A computer readable medium may be any medium capable of carrying those instructions and include a CD-ROM, DVD, magnetic or other optical disc, tape, silicon memory (e.g., removable, non-removable, volatile or non-volatile), packetized or non-packetized wireline or wireless transmission signals. 
     A method and apparatus has been described for allowing SDV system subscribers to conveniently establish limitations or controls on programming that may be viewed in a residential or other environment. The limitations or controls are implemented by the SDV manager or other appropriate entity by forcing the set top terminal or other subscriber end device to tune to an alternative program or channel instead of a program or channel that is to be blocked in accordance with pre-defined rules.