Abstract:
Alternative approaches to the insertion of local commercials and messages into networks feeds are provided. Embodiments include digital commercial insertion for cable operators and others that not only offer more flexibility and features, but may also be significantly cheaper to implement. The actual “insert” of the local commercial or message into the digital program is performed by a standard set top box, with several methods of providing the local commercial to the set top box at the proper insertion time. Another embodiment allows a cable operator to significantly save on equipment in the form of splicers and ad inserters, by allowing easy and dynamic mapping of local commercials to insertion zones.

Description:
RELATED APPLICATION 
       [0001]    The present application claims the benefit of U.S. Provisional Application No. 60/600,664 filed on Aug. 11, 2004, which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention is directed towards digital media transmission, and more particularly towards transmission of digital programs to end viewers. 
       BACKGROUND 
       [0003]    Cable operators use their infrastructure to carry programming content and deliver (sell) this to their subscribers. As part of their agreements with some programmers, the cable operator can also be allowed to insert commercial messages in those network feeds. The operator is typically allowed to do that only at selective times (sometimes called “local avails”, “avails”, “local breaks”, or “breaks”), typically 1-3 minutes per hour. The operator can choose to either sell this time to advertisers (generating extra revenue), or use the time to insert promotional messages for their own products and services. 
         [0004]    Cable operators have used the following set up illustrated in  FIG. 1  to implement local commercial insertion. The programmer typically distributes their feed via satellite  22  to the various cable operators. The feed can be analog or even digitally encoded. The feed contains signals (in the form of audio tones called “cue tones”) that indicate a local break to the cable operator. 
         [0005]    The receiver at the cable operator receives the satellite signal  20  (decompresses it in case of a digital signal), strips off the audio tone, passes through the (analog) feed  24  to the ad inserters  26 , and (separately) passes the Insertion (Control) Signal  25  to the ad inserter as well (triggered by the cue tone in the feed). The Traffic &amp; Billing system  28  is responsible for scheduling the commercial messages across the day, it feeds schedule files to ad inserters  26  (typically once a day) with today&#39;s insertion schedules. 
         [0006]    Separately (and typically at least one day before airing), the commercial messages are loaded into the ad inserters  26  (this can be encoded from tape, or transcoded from a digital format). 
         [0007]    The ad inserter  26  as shown in  FIG. 2A  typically just “passes through” the incoming analog feed, but whenever it gets an “insert” signal, as shown in  FIG. 2B , it looks in its schedule to see which message should be inserted, then looks up the message in its internal database  30 , and inserts the message into the (analog) feed. 
         [0008]    Messages can be any length (as long as they fit in the “avails” that are agreed upon between the programmer and operator), but typical lengths are 30 second, 60 seconds, or 15 seconds. 
         [0009]    Cable operators typically have the right to insert local messages on a variety of different networks. In addition to this, typical cable systems consist of multiple ad insertion zones (or ad insertion head ends). So if a cable operator serves an area (say a city) that consists of &lt;n&gt; insertion zones, and wants to insert commercial messages on &lt;m&gt; different networks, a total of &lt;n&gt;×&lt;m&gt; ad inserters are needed. This enables the operator to insert unique (different) commercial messages in each zone/network combination, but at a high cost for equipment. 
         [0010]    With the introduction of digital television, cable operators now need to upgrade their insertion infrastructure in order to be able to insert commercial messages into already compressed (digital) feeds. This new system (called DPI, or Digital Program Insertion) is illustrated in  FIG. 3 . The programmer typically distributes their feed via satellite  22  to the various cable operators. The feed is digitally encoded. The feed contains signals (in the form of special messages, such as the “SCTE  35 ” messages that are standardized for this purpose by SCTE) that indicate a local break to the cable operator. 
         [0011]    The receiver at the cable operator receives the satellite signal and passes it through (including the digital messages) to a new device called a splicer  34 . The splicer  34  (among other things) will detect the digital messages in the stream  33 , and start an interaction with the digital ad server  36  to get a digitally encoded commercial that is ready for insertion, it will then “splice” that digital commercial into the digital feed  33  during the local avail. The output signal  38  will be a digital signal with a local commercial during the local avail, and is distributed to digital reception devices at the consumers premises (typically a digital set-top box, or a digital TV set). 
         [0012]    One of the reasons why digital insertion is more complex, is that insertion (splicing) of a digital commercial in a digital feed is not as straightforward as the simple “switch” that is embedded in the analog ad inserter  26  (see  FIG. 2 ). Instead it needs a fairly sophisticated splicer  34 , which is typically external to the ad inserter  26 . 
         [0013]    Scalability for digital insertion is similar to analog insertion, if a cable operator serves &lt;n&gt; insertion zones, and wants to insert commercial messages on &lt;m&gt; different digital networks, a total of &lt;n&gt;×&lt;m&gt; ad inserters and splicers are needed. Again, this enables the operator to insert unique (different) commercial messages in each zone/network combination. 
         [0014]    One of the trends in local cable advertising is to combine all ad insertion zones and capabilities into a single “Interconnect”. An Interconnect typically covers a complete city and may consist of one cable operator, or even a combination of multiple cable operators. It essentially connects all ad inserters so that a client (e.g. an advertiser) can approach the whole market as a single entity, can place single orders, and there is a single T&amp;B (traffic and billing) system driving the insertion schedules. In addition the technical part of the interconnect is typically run from a single command location (Master Control Center). If an Interconnect covers &lt;n&gt; zones, it has the ability to (in any given local avail) air &lt;n&gt; different commercials at the same time in the same program. 
         [0015]    There is a large cost involved in converting to digital. Cable operators that “go digital” (in other words: start to distribute their signals to their subscribers in digitally compressed format) obviously face significant investments in infrastructure, digital set-top boxes or other CPE, etc. But on top of these, there is another required investment which is sometimes overlooked, namely the equipment that is needed to insert commercial messages into compressed (digital) program feeds. For a market that contains &lt;n&gt; zones and &lt;m&gt; digitally carried networks, this may add up to &lt;n&gt;×&lt;m&gt; splicers and &lt;n&gt;×&lt;m&gt; digital ad servers, which can be a significant investment. 
         [0016]    Therefore, many operators consider “collapsing” their insertion zones to save money (e.g. collapse &lt;n&gt; zones into one (or few) big insertion zones). This reduces investment, but also reduces the unique ability to insert different commercials in different zones (which advertisers can use for reasons of better targeting their messages). 
       SUMMARY 
       [0017]    The present invention provides some alternative approaches to digital commercial insertion for cable operators and others that not only offer more flexibility and features, but may also be significantly cheaper to implement. In one embodiment, the present invention includes a system where the actual “insert” of the commercial or message into the digital program is actually performed by the digital receiver that sits at the consumer&#39;s premises (this can be a set-top box, digital TV set, or other). This strongly reduces the need for sophisticated splicer and ad-server equipment at the head-end, while imposing minimal to no additional cost at the receiver devices. 
         [0018]    In another embodiment, the present invention includes a system where the actual “insert” of the commercial is performed upstream (for example, at the head-end), yet the number of unique splicers and ad servers is greatly reduced, while preserving the ability to send insert different commercials in different insertion zones. 
         [0019]    The present invention includes a method of inserting local commercials into a local feed, including receiving and distributing a digital media stream to a plurality of digital reception devices (for example, set top boxes), detecting a signal in the digital media stream indicating an insertion point, selecting a digitally encoded commercial for insertion; and sending the digitally encoded commercial to the plurality of digital reception devices, at a time as indicated by the signal indicating an insertion point. It further includes providing a signal to at least some of the plurality of digital reception devices to indicate to the some of the plurality of digital reception devices to switch to the digitally encoded commercial. The digital reception devices will switch back to the digital media stream at a time after an end time of the digitally encoded commercial. The digital reception devices may be provided with software to facilitate switching to and from the digitally encoded commercial, or may be hardcoded with firmware, Asics etc. to allow the switching functionality. 
         [0020]    The step of sending the digitally encoded commercial to the plurality of digital reception devices may be performed by multiplexing the digitally encoded commercial into the digital media stream. Alternatively, it can be performed by using a feeder channel, or a combination of these techniques. 
         [0021]    Some of the digital reception devices may receives a different digitally encoded commercial, depending on the setup of the system. For example, a plurality of digitally encoded commercials may be sent simultaneously to the plurality of digital reception devices, and a filtering process will filter out at least one digitally encoded commercial to prevent it from being received by a selected group of digital reception devices. 
         [0022]    A count may be maintained of a number of times the digital reception devices switch to the digitally encoded commercial, and a different digitally encoded commercial may provided depending upon the count. 
         [0023]    The present invention also includes a system for inserting local commercials into a local feed. A client ad server component, receives a digital media stream and distributes the digital media stream to a plurality of digital reception devices. When the client ad server component detects a signal in the digital media stream indicating an insertion point, the client ad server component sends a digitally encoded commercial for insertion to the plurality of digital reception devices, at a time as indicated by the signal indicating an insertion point. The client ad server component provides a signal (which may be the same signal as the signal indicating an insertion point, just passed on through) to at least some of the plurality of digital reception devices to indicate to those plurality of digital reception devices to switch to the digitally encoded commercial. The digital reception devices will switch back to the digital media stream at a time after an end time of the digitally encoded commercial. 
         [0024]    Another aspect of the present invention includes a system for allowing a plurality of different local messages to be inserted across a plurality of insertion zones. It includes a plurality of splicing components, one splicing component for each different local message, wherein the plurality of splicing components receiving a common network feed. It also includes a programmable switch, having an input port for each of the plurality of splicing components, and having an output port for each of the plurality of insertion zones, wherein the programmable switch is capable of mapping any input port to one or more output ports. A controller controls the plurality of splicing components and the programmable switch, to allow a different local message to be provided to a selected ones of the plurality of insertion zones. The controller can include a prioritizing function to determine the best allocation of local messages to insertion zones in case there are more local messages than splicing components. 
         [0025]    This aspect of the invention may also include a initial switch providing the common network feed to the plurality of splicing components, the initial switch to provide for changing the common network feed to a network feed which will subsequently include an insertion point for inserting local messages. Before a local message is complete, the controller can instruct the programmable switch to cause at least one insertion zone to start receiving media from a different splicing component. 
         [0026]    An advantage of the present invention include the ability to use present-day set top boxes with minimal “intelligence”, for example, without any need for a profiler to help such set top box to decide which local commercial to insert. 
         [0027]    Other advantages of the present invention include a more cost efficient way of digital commercial insertion for cable operators and others, but also an approach that inherently provides more flexibility (for example, there is no reason anymore why commercial insertion zones need to be “hard wired” and not change-able once they are done). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The foregoing and other features and advantages of the present invention will be more fully understood from the following detailed description of illustrative embodiments, taken in conjunction with the accompanying drawings in which: 
           [0029]      FIG. 1  illustrates a traditional local cable ad insertion system; 
           [0030]      FIGS. 2A and 2B  illustrate pass-through and Ad Inserter mode for a traditional ad inserter; 
           [0031]      FIG. 3  illustrates a digital local cable ad insertion (DPI); 
           [0032]      FIG. 4  shows an illustrative embodiment of the present invention for Client Insertion; 
           [0033]      FIG. 5  illustrates how to insert Commercials Within Multiplex according to an illustrative embodiment; 
           [0034]      FIG. 6  illustrates how to use Feeder Channel according to an illustrative embodiment; 
           [0035]      FIG. 7  illustrates a Shared Feeder Channel example; 
           [0036]      FIG. 8  illustrates a Unique Feeder Channels Per Zone example; 
           [0037]      FIG. 9  illustrates a Cascaded Approach example; 
           [0038]      FIG. 10  is a block diagram of a Client Ad Server Unit (CASU) according to an illustrative embodiment; 
           [0039]      FIG. 11  is a block diagram illustrating Signal Paths for Digital Insertion; and 
           [0040]      FIG. 12  illustrates an embodiment for Optimized Digital Insertion. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    The present invention provides a novel solution to allowing local insertion of content, typically local commercials or ads, into the digital feed for cable operators and other distributors. The present invention may be implemented at several different locations along the delivery process, either in one location or distributed along the delivery stream. Although the present invention is described in terms of commercials and ads, the present invention can be used for insertion of any specific media, such as messages intended for a local audience, or even customized parts of generic commercials, such as the insertion of a local store location at the end of a generic commercial. 
         [0042]    An illustrative embodiment of the present invention focusing on using Set-top boxes for insertion shall now be described. In this approach, the insertion (splicing) of commercial messages is pushed down to the individual digital set-top boxes  44  as illustrated in  FIG. 4 . The programmer distributes their (digitally encoded) feed (including SCTE  35  or other switch messages to signal local avails) via satellite  22  (or by other method) to the various cable operators. The receiver  32  at the cable operator receives the satellite signal and passes it through (including the digital switch messages) to a new device called “Client Ad Server”  40 . 
         [0043]    The Client Ad Server  40  stores commercials for later play out. Typically such commercials are already in digital form, and compressed. The Client Ad Server  40  also communicates with the Traffic &amp; Billing system  42  so that it understands which commercials are schedule for each local avail. Whenever the Client Ad Server  40  detects a digital insert message (e.g. SCTE  35  message) in the stream  33 , it does the following:
       Locates a commercial that should be “inserted” in this break, and play it out exactly in sync with the avail (either in the same multiplex, or on a separate multiplex, as described below).   Either passes through the digital insert messages to the set-top boxes  44  downstream, or alternatively replaces them with similar switch messages specifically designed to be handled by set-top boxes  44 .       
 
         [0046]    The Set-top boxes  44  are typically ordinary set top boxes, which include special switching logic, typically in the form of an embedded software application. This embedded software may be installed the Set-top boxes  44 , or alternatively downloaded to the Set-top boxes  44  through the digital feed  35  or otherwise. The software detects switch messages in the stream  35 , and uses them to “switch” to a local commercial during the insertion break. More specifically, in accordance with an illustrative embodiment, at the beginning of an avail the Set-top boxes  44  will switch to the local commercial, and at the end of a specified length of time they will switch back to the program feed  35 . 
         [0047]    When the Client Ad Server  40  plays out the local commercial exactly in sync with the local avail of the program it needs to be inserted into, there are two options for provided the commercial to the set-top boxes  44 . The first option is shown in  FIG. 5 , where the local commercials are be played out in the same multiplex as the program feed it needs to be “inserted” into.  FIG. 5  illustrates a single (MPEG) multiplexed signal  45  that carries six digital program feeds  46  (for this example, ESPN, CNN, USA, TNT, TBS, A&amp;E). These program feeds are merely illustrative and no claim is made to those networks or any affiliation with any such network. The multiplex  45  also has two reserved feeds  48  that are only used during a local avail on any of the six programs  46 . Precisely during each of these local avails  50 , the reserved feed  48  will carry the local commercial  52  so that the set-top boxes  44  (not shown) can “switch to” and “switch from” the commercial  52  at the beginning and end of the avail  50  respectively. 
         [0048]    This approach requires some bandwidth to be reserved in every multiplex  45  that carries digital programs  46  that need local ad insertion. The amount of bandwidth depends on how many overlapping local breaks  50  can occur amongst the digital program feeds  46  within the multiplex  35 , in the example there are two reserved feeds  42  so its is possible to handle up to two overlapping avails  50 . Other numbers of reserved feeds  42  are possible and within the scope of the invention. Further, there is some room for optimization beyond the number for reserved feeds  42 , for example it may be a good idea to concentrate the most valuable program feeds  46  in few multiplexes  45  that have a relatively high number of reserved feeds (for example, four), whereas the less valuable program feeds  46  are carried in multiplexes  45  with lower number of reserved feeds. This would have the effect that the chances of “losing” an avail on valuable feeds  46  is less than loosing an avail on a less valuable network  46 . 
         [0049]    The second option is shown in  FIG. 6  and involves playing the local commercials in a dedicated feeder channel.  FIG. 6  illustrates a number (in this case four) of MPEG multiplexes  45 . The first three multiplexes (Mux  1 - 3 ) carry regular digital program feeds  46  (depending on encoding and modulation, there typically may be as few as seven, or more than twelve program feeds in the multiplexes). The fourth multiplex, Mux- 4 , is reserved for all local commercials, it is also known as the feeder channel. 
         [0050]    The regular program feeds contain local avails  50 . Precisely during each of these local avails, the feeder channel Mux- 4  will carry the local commercial  52  so that the set-top boxes can “switch to” and “switch from” it at the beginning and end of the avail  50  respectively. 
         [0051]    The feeder channel can either be a fully dedicated multiplex/QAM (Quadrature Amplitude Modulation), but it can also be a reserved part of a multiplex/QAM that is partly also used for other services. The amount of bandwidth that has to be reserved in the feeder channel depends on how many overlapping local avails the operator wants to be able to handle with this system. This allocation can be fine-tuned by the cable operator as a trade off between bandwidth and returns. 
         [0052]    Each of these embodiments has certain advantages. The first embodiment, within the multiplex  45  has the advantage very simple implementation in set-top box, and can do a cleaner (seamless) splice even with basic set-top boxes. However, it tends to use more bandwidth and may require more sophistication at the head-end, because of the need for re-multiplexing instead of simple play out. The second embodiment, using a feeder channel, has optimal bandwidth efficiency. However it may require more integration in set-top box software (for example, the need to access the tuner). Also, a seamless splice is somewhat more difficult, however this can be fixed by having black frames around the commercial. It is also possible to mix both approaches to achieve the best combination of simplicity, bandwidth efficiency, and other features for a general solution, and also specific requirements. 
         [0053]    Focusing now on the Client Ad Server  40 , there are a number of different options on the number and location of Client Ad Servers  40  in the cable operators network. In a first centralized example, consider a cable operator in a market that has 50 insertion zones, and 40 networks feeds that require local commercial insertion. We assume that the cable operator uses the Feeder Channel approach to preserve bandwidth. The cable operator may decide to use 40 Client Ad Servers (one for each network feed) and place them at a central location in the system (for example the Master Control Center) to feed all insertion zones. 
         [0054]    Now let&#39;s look at a local avail  50   FIG. 7  in one of the network feeds  46  (say ESPN). Let&#39;s assume the cable operator wants to insert 10 different commercial messages  52  in this local break (one in zones 1-5, one in zones 6-10, etc.). Since there is only one Client Ad Server (not shown) that is shared between all 50 insertion zones, the (bandwidth in the) Feeder Channel  45   d  is also shared. In this scenario the individual set-top boxes will be instructed which commercial message to select (which will depend on the insertion zone they are member of). 
         [0055]    Turning now to a decentralized option, the system can be implemented with a Client Ad Server  40  per insertion zone (so for this example, fifty in total). In the same local insertion example (ESPN, ten commercials) each of the Client Ad Servers  40  will only insert one commercial  52  in the Feeder Channel (namely the one that is intended for its specific insertion zone), as illustrated in  FIG. 8 . In this scenario, the set-top box does not need specific (zone dependent) instructions in order to “pick” from multiple local commercials  52 , making this implementation simpler. 
         [0056]    A final example shown in  FIG. 9  provides a cascaded approach, where a single Client Ad Server  40  per network feed is used in combination with a number of “filter” units  56  downstream to optimize bandwidth usage. This approach puts a single Client Ad Server  40  (per network feed) in a central location (similar to example 1), which would transmit a feeder channel with all different local commercials in it over the backbone network  54  to each head-end or node  55  (similar to  FIG. 7 ). However at the head-end or node  55  (where the backbone network terminates and is connected to the “Last Mile” coax network  58 ) a special filter  56  strips the feeder channel from all local commercials but the one that is relevant for this insertion head end  55 , so the actual feeder channel that is transmitted to the individual homes looks like  FIG. 8 . Examples of filter units  56  may be an existing edge device such as an edge-QAM modulator, that simply only passes one of the feeder channels through, ignoring all others. It could know which one to pass through by configuring it at installation time, so every QAM would be configured to “pass” unique feeder channels). Other possible approaches are also within the scope of the invention. 
         [0057]    An advantage of this setup is only one Client Ad Server  40  is needed per network feed, and the Set Top Box does not need specific (zone dependent) instructions for picking the proper local commercial. 
         [0058]    An illustrative implementation is a cascaded approach with a feeder channel. In this implementation, a single Client Ad Server Unit (CASU)  60  is installed at a central location in the cable operators network (e.g. at the Master Control Center). The CASU  60   FIG. 10  performs the following tasks:
       It passes through all digital program feeds  46  of programs that have local avails, and detects incoming insert messages (it also passes these insert messages through, or generate set-top box specific ones, as previously described).   It manages the Central Feeder Channel  62  (which is carried to each head-end over the backbone network), and plays out all required local commercials on the Feeder Channel  62  during each relevant local break   It has a network interface  64  for loading/unloading new commercial messages that it (may) need to insert locally.   It has an interface to Traffic &amp; Billing systems  42 , so that it knows which local commercials should be inserted across the whole market in a specific break. It can also maintain logs of which local commercials have been viewed a certain number of times (broken down by zone, if helpful), and can choose to substitute/rotate through different commercials based on any desired formula.
 
The CASU  60  functions as follows:
   There is an interface  64  for loading new local commercials onto the CASU  60 , and removing commercials off of the CASU  60  when they are no longer needed. Local commercials are loaded in digitized form and stored  68 . This interface can be driven by an asset management system, or by a local operator. Local commercials are given a unique identifier when loaded on the CASU.   The T&amp;B System  42  has a dedicated interface for loading scheduling information into the CASU  60 . This information basically defines which local commercial needs to be inserted in which feed under which conditions (time, etc.). The CASU  60  stores this scheduling information in its internal schedule database  66 .   Up to forty network program feeds  46  can enter the CASU  60 . Although forty feeds  46  were chosen because cable operators typically insert into forty networks only, this selection is arbitrary and can be any number of feeds. These feeds  46  may contain digital insert messages to signal a local avail. The CASU  60  will pass through the feeds and whenever there is a local avail, it will access its internal database  66  to determine which local commercials need to be inserted, and play these commercials on the Central Feeder Channel output port  62  exactly during the local avail. In addition it may also be necessary to send some additional information to the set-top boxes downstream (either by inserting additional information in the program feeds, or otherwise), this information may include where in the central feeder channel  62  the local commercials are played out. The forty input feeds, forty output feeds, and central feeder channel output feed can physically be mapped on connectors such as DVB-ASI, DVB-DHEI, or any other interface. It is also possible to map/combine multiple logical inputs and/or outputs into one physical connector.   The CASU  60  will also manage bandwidth of the central feeder channel. For example if the system only has bandwidth to deal with &lt;n&gt; overlapping local commercials, and there actually are more than &lt;n&gt; overlapping commercials scheduled, it may either request additional bandwidth or select the &lt;n&gt; local commercials that can be served. It can do that based on simple “First-Come-First-Served” selection, or based upon more sophisticated algorithms that select the commercials with the highest value.       
 
         [0067]    A second useful component of this system is a Filter Unit  56   FIG. 9  that sits in each insertion zone. It simply takes the central feeder channel  62   FIG. 10  as an input (containing all different local commercials during each break) and strips out all but the one that is intended for this insertion zone. It produces a Local Feeder Channel that is then transmitted to the homes (and set-top boxes) in the zone. The filter unit  56  basically makes the Set top box&#39;s job simple by avoiding needing the set top box to have intelligence to pick the correct insertion commercial. 
         [0068]    Another component of this system is a software application that resides in the set-top box  44 . The application can be resident or downloadable, it does not have a user interface, does not need a return channel per se, and performs the following functions:
       When started the application goes into “passive mode” and starts “listening” to digital insert messages in the current program feed.   Whenever an insert message is detected, the location of the local commercial in the local feeder channel is retrieved. Examples of retrieval include providing the commercial with the insertion message, or the commercial can be communicated to the set top box separately. The application retunes the set-top box to that local commercial at the start of the local avail, and tunes back to the original program feed at the end of the local avail. Typically, this will all be transparent to the user.       
 
         [0071]    Another embodiment of the present invention is based on the notion that the current network topology (with individual inserters per insertion zone) is in many cases may be overkill.  FIG. 11  shows the signal paths for digital insertion in a single program feed by a cable operator that has &lt;n&gt; insertion zones (for the sake of simplicity each combination of a splicer  34  and a digital ad server  36  is represented as a single box) 
         [0072]    This setup gives the cable operator the ability to insert (in a given local avail) a unique and different local commercial in each insertion zone. In reality however, in most cases the cable operator will either insert the same local commercial in all zones, or only a limited set of different local commercials mapped on the various insertion zones (for example in a market with fifty insertion zones, there may be five different commercials, the first going to zones 1-10, the second one going to zones 11-20, etc.). Another way of saying this is that in the traditional setup of ad insertion (such as in  FIG. 11 ) the system is dimensioned for the worse case usage scenario, but does not take advantage of the fact that statistically the cable operator will only use a fraction of that. 
         [0073]    An alternative setup for digital program insertion according on an embodiment of the present invention is shown in  FIG. 12 . This setup allows for a maximum of &lt;m&gt; different local commercials to be inserted across &lt;n&gt; insertion zones. This setup consists of the following components:
       A total of &lt;m&gt; splicer/ad-server combinations  34 ,  36  are set up, all connected to the incoming program feed.   A programmable switch  70  is set up. It has &lt;m&gt; input ports  72 , and &lt;n&gt; output ports  74 , and can be programmed to map any input port onto any combination of output ports. Its input ports are connected to the output ports of the splicers  34 , 36 . Its output ports are connected to each insertion zone.   A controller  76  is provided. It interfaces with the T&amp;B system  42  on one hand, and with the splicer/ad-servers  34 ,  36  and programmable switch  70  on the other hand.
 
The system operates as follows:
   The T&amp;B System  42  communicates scheduling information to the controller  70 , who stores this in its internal database.   Whenever there is a local avail, the splicers  34  will detect it (through the presence of digital insertion messages) and inform the controller  76 .   The controller  76  will then determine which local commercials need to be inserted in which insertion zones, and assign each unique local commercial to exactly one splicer/ad-server  34 ,  36  pair. The controller  76  will also program the switch  70  so that the output of each splicer  34  is mapped to the correct insertion zones.       
 
         [0080]    Because of time and scheduling, the controller  76  typically will know in advance when a local avail is coming up, and can ‘preprogram’ the switch  70  to divide up the interzones by appropriate splicer  34 . This setup may be left in place until a next local avail comes up which has a different combination of commercials or insertion zones. Since the splicers  34  are passive when not inserting local commercials, the system will run normally during normal broadcast, no matter how switch  70  has mapped the splicers  34  to insertion zones. 
         [0081]    This embodiment is flexible with respect to the choice of the maximum number of unique commercials. Obviously a lower number will create greater cost savings but will also limit flexibility. If in a system with fifty insertion zones (n=50) it would be acceptable to set the maximum number of unique commercials to ten (m=10), this system would create an 80% cost savings on splicer/ad-server pairs when compared with the traditional setup. Further, it is expandable on an incremental basis. 
         [0082]    In this embodiment, some of the components may be combined into other physical system components. For example the programmable switch  70  may be a separate unit, or integrated with the controller  76 , or even be an integral part of the network (depending on what network is used to distribute program feeds to the insertion zones, this may already be a feature that is built into that network). It should be noted that it is also possible to combine these various approaches to create unique trade offs between investment, features, etc. It should be noted that the present invention can be combined with features described in other pending commonly owned patent applications, including U.S. patent application Ser. No. 09/735,983, entitled Seamless Switching and filed on Dec. 13, 2000; U.S. patent application Ser. No. 10/369,047, entitled Seamless Switching and filed on Feb. 19, 2003; U.S. patent application Ser. No. 10/192,192, entitled System And Method For Seamless Switching Of Compressed Audio Streams and filed on Jul. 9, 2002; U.S. patent application Ser. No. 10/423,280, entitled System And Method For Optimized Channel Switching In Digital Television Broadcasting and filed on Apr. 25, 2003; and U.S. patent application Ser. No. 10/991,674, entitled System And Method For Optimized Encoding And Transmission Of A Plurality Of Substantially Similar Video Fragments and filed on Nov. 18, 2004; which are fully incorporated here by reference. 
         [0083]    Although this description is written from the perspective of a cable operator, it is straightforward to apply the same approaches to other network operators as well (for example broadcast networks with affiliates, cable networks with local reception points at head-ends, etc.). 
         [0084]    Although the invention has been shown and described with respect to illustrative embodiments thereof, various other changes, omissions and additions in the form and detail thereof may be made therein without departing from the spirit and scope of the invention.