TARGETED MEDIA CONTENT

TECHNICAL DOMAIN

The present invention relates to the domain of digital media players or recorders, especially where presentation of particular media content according to a user's viewing habits is made possible. The invention also involves characteristics pertaining to the domain of conditional access to media content.

STATE OF THE ART

Business models used in the domain of presentation of media content have long taken into consideration that advertising content can generate revenue. One of the ways in which media content can be made available to a user is via a personal digital video recorder or player. Such players, being of a personal nature in that they are generally used by one particular user, present the possibility of recording the user's viewing habits. Other means for presenting content also allow for the possibility of monitoring the user's viewing habits, such as a personal computer for example. Through the use of a plurality of user profiles, one for each user of any of the above examples of such apparatus, a plurality of user profiles can be used to keep track of a plurality of different users' viewing habits.

Given these possibilities, advertisers see particular advantage in being able to present advertising content targeted towards a particular viewer based on his viewing habits and indeed are prepared to pay considerable fees for such a privilege. Some viewers, on the other hand, given the choice, tend to prefer not to view advertising content and even take an active part in avoiding such content by skipping over it, a feature which is facilitated by the trick mode playing controls which are generally offered in the media players which comprise the object of the present invention. Advertisers therefore have an interest in trying to prevent viewers from engaging in these avoidance techniques.

International Patent Application Publication number WO 2009/152447 A2 describes a system and a method from a neighbouring domain of presentation of broadcast television content, where it is desirable to present advertising content together with the broadcast content on a mobile device. The publication discloses the addition of a tag within the broadcast content, the tag comprising an instruction to present a particular piece of advertising content preloaded on the mobile device. The publication does not disclose selecting the advertising content based on a user profile based on the user's past viewing habits, nor does it suggest how to enforce the playing of the advertising content or to guarantee that the advertising content has been played before allowing the content selected by the user to be played.

United States Patent Application Publication number 2012/0167132 A1 discloses a technique for inserting advertisements into video streams for playback on media players. The insertion of advertisements is based on a user profile, which may include such things as the viewer's location or the viewer's previous viewing habits. However, no mention is made of how to enforce the playing of an advertisement nor of how to ensure that the advertisement is played in its entirety before allowing the user to view the content of his choosing.

Likewise, United States Patent Application Publ ication 2008/0307454 A1 shows how to insert targeted advertising material , using a user profile, during playback of video media, but fails to address the problem of how to prevent the viewer from skipping over the advertisement.

United States Patent Application Publication number 2009/204,541 A1 describes a system for forcing viewing of advertising content when another, particular content is viewed. The system uses a chain of encrypted permission keys placed at intervals within the advertising content, the advertising content being embedded within the particular content. If the advertising content is not played in its entirety, then one or more permission keys will be missing. Since the playing of a piece of particular content relies on a predetermined sequence of permission keys having been received, any attempt by the viewer to alter the predetermined sequence of playing will result in a loss of one or more keys with respect to the predetermined sequence, thereby possibly preventing part of the particular content from being played (since the predetermined sequence includes the advertising content being played in its entirety, within the playing of the particular content). The system also works when a viewer copies content since it forces the viewer to copy the whole sequence of content including the advertising content whereas he would have been inclined to copy the particular content without the advertising content. Since it is the provider who fixes the sequence and the advertising content and its position in the sequence, it is the provider who has the ability to predetermine what sequence of content the viewer has to copy in order to be able to view the content he actually ordered (the particular content).

United States Patent Application Publication number US2002/092,019 A1 gives a detailed description of advertising content delivery using viewer demographic data. Advertising content is del ivered to a viewer based on a match between demographic data corresponding to the viewer and one or more tags associated with the advertising content. No forcing of actual consumption of the thus targeted advertising content by the viewer is implied in this document. However a system is described whereby a viewer is encouraged to view the targeted advertising content by offering incentives or rewards. BRIEF SUMMARY OF THE INVENTION

In view of the prior art, advertisers may perceive greater leverage on the returns on their investments if they could be provided with a means for enforcing the playing of advertising content of particular interest to a viewer at a time when the viewer is particularly receptive to such content. Additionally, benefits to the advertiser may be gained if such enforcement were ensured or otherwise authenticated, thus giving the advertiser a guarantee that the advertising content had been played through before allowing the content of interest to the viewer to begin playing. Further advantage may be gained when the advertiser can be assured that unscrupulous third parties are not able to interfere with the process for selecting targeted content or even to replace targeted content for content whose rendering would provide no gain to the advertiser. Furthermore, it is advantageous that advertising material for a particular viewer be selected according to that viewer's tastes, usually determined according to his past viewing habits for example.

More particularly, there is a need for locally-supported enforcement of a policy whereby playing of viewer-selected content is prevented until playing of a targeted piece of advertising content on the viewing device has been authenticated. In this way, the content provider only has to deal with providing the content selected by the viewer and does not have to deal with making sure that any advertising content has first been viewed. The advertiser also gains in the knowledge that the viewer's device alone will be in a position to guarantee that advertising content of particular interest to the viewer will be played on the viewer's device before allowing the viewer to view the content of his choice. This allows for a much more flexible system since the provider does not have to deal with all the different configurations necessary for managing all the different types of advertising content of particular interest to a large population of viewers having different tastes, neither does he have to deal with checking that the advertising content is actually played before sending the selected content.

Ideally, the user equipment should deal with enforcing playing of targeted advertising content and allowing playing of viewer-selected content only once the playing of the targeted advertising content has been authenticated. Embodiments of the present invention make this possible even if the viewer's local equipment is a standard one in the sense that it has not been particularly adapted to perform these functions. It is only necessary that the viewer's equipment be configured to receive a conditional access module, usually via a slot compatible with the Common Interface Standard (CI or CI+), with an embodiment of the present invention being deployed in the conditional access module. The operator or content provider simply has to provide a predetermined number of dummy data packets within the viewer-selectable content in order to maintain proper sychronisation of the viewer-selected content once the non-solicited content has been inserted into the data stream at the host end. To this end, according to a first aspect, the present invention provides for a method for enforcing presentation of at least one from a plurality of unsolicited media content objects on a host device for presenting media content objects;

the host device being configured:

to allow a user to select at least one selectable media content object; and to be connected to a conditional access module;

the user-selected media content object:

being associated with at least one first characterising element; and

comprising a predetermined number of dummy data packets; the plurality of unsolicited media content objects each being associated with at least one second characterising element;

wherein the conditional access module:

comprises a content buffer; and

has access to a first storage device for storing the plurality of unsolicited media content objects;

the method comprising:

storing at least part of the user-selected media content object in the content buffer;

updating, by the conditional access module, a profile record corresponding to the user, by recording a tag based at least on the first characterising element associated with the user-selected media content object;

selecting, by the conditional access module, the unsolicited media content object based on a comparison between the updated profile record and the second characterising element;

sending the selected unsolicited media content object to the host device for playback, the selected unsolicited media content object comprising a number of data packets substantially equal to the predetermined number of dummy data packets; filtering the predetermined number of dummy data packets from the user- selected media content object; and

sending the filtered user-selected media content object to the host device after the unsolicited media content object has been sent.

According to a second aspect, the present invention provides for a media content rendering system (100) comprising:

a first storage device (120) for storing at least one first media content object

(122), the first media content object (122) being associated with at least one first characterising element (124);

a second storage device (130) for storing at least one second media content object (132), the second media content object (132) being associated with at least one second characterising element (134);

a host device (1 10) for rendering at least the first media content object (122), the host device (1 10) comprising means for selecting the first media content object (122) based on a request from a user; and a conditional access module, connectable to the host device and configured to receive the first media content object from the host device and to return at least part of the first media content object to the host device, the conditional access module further configured to:

execute a profile management application (150) to edit an editable profile record (140) at least by logging a tag (144) based at least on the first characterising element (124); and

execute a media content selection application (155) to select the second media content object (132) based on a comparison between the tag (144) and the second characterising element (134);

the media content rendering system (100) characterised in that:

the second media content object comprises a predetermined number of dummy data packets; and

the conditional access module further comprises a content buffer to buffer at least part of the first media content object;

the conditional access module being further configured to:

send the second media content object to the host device for playback;

filter the dummy data packets from the first media content object; and send the filtered first media content object to the host device after the second media content object has been sent.

According to yet a third aspect, the present invention provides for a conditional access module for use with a host device for presenting a media content object, the host device (1 10) comprising means for selecting the first media content object (122) based on a request from a user, the conditional access module having access to: a first storage device (120) for storing at least one first media content object

(122), the first media content object (122) being associated with at least one first characterising element (124);

a second storage device (130) for storing at least one second media content object (132), the second media content object (132) being associated with at least one second characterising element (134);

the conditional access module being configured to:

receive the first media content object from the host device and to return at least part of the first media content object to the host device; execute a profile management application (150) to edit an editable profile record (140) at least by logging a tag (144) based at least on the first characterising element (124); and

execute a media content selection application (155) to further select the second media content object (132) based on a comparison between the tag (144) and the second characterising element (134);

the conditional access module characterised in that:

the second media content object comprises a predetermined number of dummy data packets; and

the conditional access module further comprises a content buffer to buffer at least part of the first media content object;

the conditional access module being further configured to:

send the second media content object to the host device for playback;

filter the dummy data packets from the first media content object; and send the filtered first media content object to the host device after the second media content object has been sent.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood thanks to the detailed description which follows and the accompanying drawings, which are g iven as non-limiting examples of embodiments of the invention, namely:

Figure 1 , which shows a block diagram of a system according to an embodiment of the present invention.

DETAILED DESCRIPTION

A system (100) in which an embodiment of the present invention may be deployed is now described with reference to Figure 1 . A media player (1 10), such as a personal video recorder, for example, has access to media content (122) stored in a storage device (120). A user of the media player (1 10) may therefore select and play a particular content (122) of interest to him. The content (122), once identified, may be read from the storage device (120), which may be a hard disk within the media player for example or it may be a file stored remotely from the media player and accessed by the media player to be downloaded for viewing. The content (122) is associated with at least one characterising element (124) or a classifier, indicating the nature of the content (122). Such characterising elements (124) are useful for describing or otherwise categorising the content (122). The characterising element (1 24) is chosen from a predetermined set of a plurality of different characterising elements (124) and is designed such that a viewer who selects a first content would be likely to be interested in a further content should both contents be associated with the same characterising element. As a particular content may be associated with a plural ity of characterising elements, it is also possible to have more complex arrangements whereby a viewer who selects a first content which is associated with a first plurality of characterising elements would probably also be interested in a further content being associated with a second plurality of characterising elements, each plurality of characterising elements allowing for a particular pattern to be deduced and each pattern allowing for comparisons to be made in order to detect similarities between the contents. The media player also has access to a different type of content, preferably advertising content (1 32), wh ich is stored on a second storage device (1 30). According to one embodiment the second storage device (130) is local to the media player (1 10) and indeed may be comprised within the media player (1 10), whereas according to other embodiments the second storage device (130) may be remote from the media player (1 10), and would in this case be accessible via a remote link. Where the second storage (130) device is local to the media player (1 10) it may even be combined with the first storage device (120) in that the first and second storage devices form part of one common storage module (190). The advertising content is also associated with at least one characterising element (134), which serves the same purpose as the characterising elements associated with the content (122) selectable by the viewer.

Whereas the first type of med ia content described above is generally selectable by a user, the second type of content, or advertising content, is not generally selectable by the user and will usually be imposed without particular intervention from the user. For this reason the first type of content may be described as solicited content while the second type may be described as unsolicited content. According to the embodiment, when the viewer selects a piece of content (122) a profile management application (150) is executed by the media player in order to update a profile record (140) associated with the viewer. The profile record is editable in that each time a piece of content is selected the profile may be updated by the profile management application in order to keep a log of what the viewer has selected for viewing. Logging may com prise s i m ply copyi ng a l ist of th e characterising elements associated with each piece of content selected by the viewer or logging a tag derived from one or more characterising elements associated with the content selected by the viewer. The tag may be a summarising value which could be a digest of all or part of the characterising elements associated with the content selected by the viewer or it may be simply the characterising element itself.

Accord ing to embod iments of the present invention, playing of content selected by the viewer is deferred pending a particular condition, the particular condition being that a piece of content selected by the media player from the second storage device is played first.

In order to facilitate selection of the content from the second storage device, i.e. the advertising content, the media player further has access to a media content selection application (1 55). This application selects a piece of content from the second storage device depending on a comparison between the user profile on one hand, the profile having been edited to reflect the viewer's viewing habits based on all or part of the characterising elements associated with the content he selected from the first storage medium and the characterising element or elements associated with the advertising content on the other hand.

According to embodiments of the present invention, the media player further has access to a conditional access module. The conditional access module may be any of the known types generally used in the Pay-TV industry and can be detachable from the media player and preferably comprises a security module for holding secret keys and the like. Deferral of the playing of the content selected by the viewer is achieved by asserting a condition whereby the selected content is locked until such times as advertising content selected by the media content selection application has first been played through. Authentication that this condition has been met is provided through the conditional access module. The conditional access module generates a release signal indicating that the condition has been met. The release signal may come in the form of a digital signal or it may be in the form of a decryption key. The locked condition of the viewer-selected content may be asserted through the selected content being in an encrypted state whereby decryption requires a decryption key or through the media player having a lock feature whereby playing of the content is not allowed unless the release signal is provided. In either case, the release signal is provided by the security module on condition that the advertising content has first been played. In the first case, the media player has access to a decryption module, which may be comprised within the conditional access module or may be comprised in the media player itself. The signal (or key) is obtained from the security module once the advertising content has been played.

According to other embodiments of the present invention, the editing of the profile may be based on inputs directly from the user as well as or instead of simply being based on characterising elements associated with user-selected content. In this manner the user's own inputs such as "like" or dislike", indicating his preferences towards any content that he has viewed, could be used as a basis for editing the profile. Alternatively, the system may provide the user with prompts requiring the viewer to give his opinion on certain types of content, the opinions then being used as a basis for editing the profile. Such profiles may evolve over time and may therefore be updated over time. A record of an evolving profile over a cyclic period may be kept. For example, a viewer's tastes may also on the time of day or day of the week, with a tendency towards informative content just after dinner time for example or towards sport on weekends and so on. Rather than building up a profile by having the viewer respond to prompts, an automatic profile-building process may be employed whereby automatic monitoring of a special content identifier in the ECM, allowing to evaluate a content type or genre, or a piece of information within the EIT allowing to make the same such evaluation could be undertaken while the viewer is watching and thereby building up the profile.

In more general terms one or more profiles may be associated with one or more users of a reception apparatus or with a CAM, the profile being built based on viewing habits of the concerned user. The profile can then be used to select which content to use as targeted content in the context of an embodiment of the present invention, such selection thereby being targeted to the particular viewer. Similarly, the profile can be used in a management policy for the management of the second storage device according to embodiments of the present invention, whereby the profile is used to determine which content will be stored on the second storage device or to determine which content should be removed from the second storage device, based on evolution in profile, rendering some targeted content less interesting to the viewer. However, other means may equally be employed for determining which content should be removed from the second storage device, such as statistical analysis based on the number of times a particular content is watched or simply by the date associated with a particular content, for example. Content can be compared with the profile in order to determine whether or not the content is of interest to the viewer having that profile.

Various techniques are known within the industry to associate a content characterising element with a piece of content. For example, a content characterising elements may be included in a header associated with the content or may be comprised in an ECM associated with the content.

Automatic profiling of the nature described above may be done without soliciting any particular intervention from the user. It may not even require the viewer to identify himself, and therefore the profile becomes associated with the viewing apparatus rather than a particular viewer, although if large variations in profiles between a plurality of users is detected, it may become possible to deduce that different viewers have been viewing content.

In embodiments where the rendering medium allows for broadcast content to be rendered, other useful information in forming a profile is to note which types of programmes the viewer actively switches towards and continues to view, and which programmes the viewer actively switches away from. This is a way to compile a table of likes and dislikes for example.

Concerning the supply of the release signal to the media player, this may be achieved by arranging for the advertising content to have encrypted markers placed at predetermined intervals throughout the advertising content, for example at least near the beginning and near the end. In this case there is an added requirement whereby in order to make sure that the viewer has not skipped any part of the advertising content all of the encrypted makers have to be decrypted. The media player can then further base the condition for unlocking the viewer-selected content on whether or not all of the markers have been properly decrypted.

As is generally known in the Pay-TV domain, use can be made of ECMs and/or EMMs to provide the security module with the necessary keys, useful for embodiments where the release signal is a decryption key.

According to yet another embodiment of the present invention, the advertising content may be structured as a carousel of content objects, typically a DVB DSMCC carousel. Using a carousel means that a content object is always available in a loop until the complete content has been successfully recovered. Each time around the loop another part of the content object is recovered until after a number of loops the complete content is fetched. Hence, the real-time constraints are somewhat eased. An example of such real-time constraints is that the media content rendering device may miss the first appearance of the content in the carousel and would then be able to get it when it next appears.

In order to prevent an unscrupulous user of the system described herein, a yet further embodiment of the present invention allows for the advertiser to maintain control over the selection of targeted media content. In this embod iment the characterising elements associated with the target content are encrypted . This prevents an unscrupulous user from interfering with or otherwise modifying the characterising elements in an attempt to corrupt the system. For example an unscrupulous user could insert blan k content or n ul l content in place of the advertiser's targeted content and arrange for such inserted content to be associated with characterising elements at least greatly increasing the probability of the inserted content of being selected. Alternatively an unscrupulous user could attempt to alter the characterising elements associated with either of the selectable content or the targeted content (or both) in an attempt to prevent advertising content from being selected. By encrypting the characterising elements and requiring that the conditional access module be used to decrypt the characterising elements the selection process executed by the content selection application becomes protected . According to another embodiment the characterising elements associated with the user-selectable content may also be encrypted and may also require to be decrypted by the conditional access module.

Systems in which an embodiment of the present invention may be deployed comprise a media content rendering device having access to a first storage device for storing media content for selection by a user and further having access to a second storage device for storing media content from which a targeted media content object will be presented to the user before he is allowed to view his selected content. By targeted it is meant that the content will match the user's preferences as evidenced by a profile record which is updated according to any content selected by the user. Each user-selectable content is associated with at least one characterising element useful in describing the content and useful in deriving a tag for updating the profile record. The tag may either be the characterising element itself or it may be a digest of one or more characterising elements from one or more user-selected content objects. Selection of the targeted content is done using a content selection application and is based on the contents of the profile record, whereby a comparison between at least one tag from the profile record is made with at least one characterising element associated with the targeted content in order to determine the most appropriate content which should match the viewer's interest. The system further comprises a conditional access module to enforce the playing of a targeted content before any user-selected content is played. Realisation of the embodiment of the invention is achieved when the system performs a method comprising: selecting the content from the first storage device; holding the selected content in a locked condition; generating a tag based on at least one characterising element associated with the thus selected content; editing the profile record using the tag; selecting, by the system, a content object from the second storage device, said selection based on a comparison between the tag and at least one characterising element associated with the object from the second storage device; playing the content from the second storage device; detecting, by the conditional access module, an end to the playing of the content from the second storage device; sending a release signal from the conditional access module to the media content rendering device if the end has been detected; removing the locked condition from the held user-selected content if the release signal is available; playing the user-selected content if the locked condition has been removed. The first storage device may be a memory or a d isc with in the content rendering device or locally attached to the rendering device. The user-selectable content may then either be pre-loaded onto the first storage device or it may be downloaded from a remote server via a remote communication link and stored on the first storage device. According to another embodiment the first storage device is remote from the media content rendering device and the content is downloaded via a remote communication link to the media content rendering device. In any of the above cases, following selection the content is held in a locked state whereby rendering of the content is prohibited until a release signal is made available. An example of a system in which an embodiment of the present invention may be deployed is a personal video recorder (PVR) for (or personal media player) for playing video on demand, the PVR comprising, or otherwise having access to, a conditional access module. The invention creates an incentive for advertisers to provide advertising content for the system described, as the advertiser can have a high level of confidence that advertising content of particular interest to a particular viewer to which the PVR belongs will actually be seen by that viewer. Great flexibility is provided since a particular PVR will be locally enabled to select advertising content of interest to the viewer and autonomously authenticate that the advertising content will be played before the viewer sees his selected content. Advertising content may be preloaded onto a memory of the PVR, from where the advertising content considered to be of particular interest to the viewer is selected, or the PVR may be configured to download the advertising content of particular interest to the viewer.

An advertiser who pays for his advertising material to be visible, or an agent towards whom an advertiser turns to maximise the visibility of his advertising material, may therefore choose to pay to be able to include advertising material on, or otherwise provide access to advertising material by, a PVR in which an embodiment of the present invention is deployed. In this way the advertiser or the agent can be assured that his adverts are being played to a targeted audience and not skipped or otherwise deleted by the targeted audience. According to an embodiment in which the user-selectable content is stored in a storage device which is remote from the media content rendering device (media player), it is convenient for the release signal to be used to authorize downloading of the content previously selected by the user. That is to say that once the user selects the content its transfer to the media player is deferred until such time as the release signal is made available by the conditional access module.

Different methods are possible for holding the user-selected content in a locked condition . According to one embodiment the user-selected content is in encrypted format and the conditional access module with its security module supplies a release signal in the form of a decryption key which will allow the content to be decrypted. The release signal is supplied on condition that the targeted content has first been played. According to another embodiment the user-selected content is held in a locked buffer and the release signal, supplied as described above, is used to unlock the buffer.

Different methods are possible for ensuring that the targeted content is played before the user-selected content. According to one embodiment the targeted content has encrypted markers pre-placed at intervals within the content. The conditional access module can decrypt the markers thanks to the security module. If the markers decrypt correctly then it can be assumed that the content up to that marker has been properly played. Having the markers appropriately placed within the content therefore allows for checking that the content has been played. Decrypting the markers avoids unscrupulous third parties from being able to add their own markers to the targeted content or to otherwise supply markers to the system in an attempt to fool the system into falsely deducing that the content has been played through.

Any of the known methods from the Pay-TV domain for passing authorisation rights and for passing decryption keys to authorised security modules can be used in embodiments of the present invention, i.e. the use of ECMs and EMMs for example. An example was given above in which an embodiment of the present invention could be deployed in a personal media player. Another case where embodiments of the present invention may be deployed in an advantageous manner is any situation where it is required to enforce playback of unsolicited yet targeted advertising. For example on any host device such as a set-top box or a digital TV or media player, especially where that host device has not been configured in any particular way to perform such enforcement. For this it is necessary for the host device to be configured to operate with a conditional access module. Usually such hosts have a slot to receive the conditional access module. Known conditional access modules include those which conform to the Common Interface Standard (CI or CI+).

Such host devices, when coupled to a conditional access module in which an embodiment of the present invention is deployed, can be made to enforce the playback of targeted advertising even though they have not been particularly adapted to do so, thereby provid ing advertisers with an incentive to invest in making advertising content since they can be sure that their content will be played in its entirety, with the user being prevented from intervening during playback of the advertising content or otherwise attempting to skip the advertising (or unsolicited) content.

According to the embodiment, the conditional access module stores and updates the profile record and further stores advertising content as described above, so that the advertising content selected by the conditional access module for playing can be matched to the user's viewing habits or to a particular content which the user has just chosen to watch. In this embodiment the selectable content is prepared in advance by including extra data packets over and above the data packets which would normally be used to represent and allow playback of the selectable content. The extra data packets do not comprise content of any interest to the user but rather function as placeholders to pad out the content and which will be replaced by data packets of advertising content. The extra data packets are otherwise known as dummy data packets. When the user selects a media content object for viewing, the content, including the dummy data packets, is received by the host device. The host device passes all of the received packets (sequentially) directly to the conditional access module, just as a host would normally do when functioning with a conditional access module, and the conditional access module filters out the dummy data packets, with the "intention" of replacing them with packets of targeted advertising content. The conditional access module then sends the content, including the targeted advertising content, back to the host device for playback. Since the dummy data packets have been accounted for by a similar number of advertising content data packets (i.e. effectively "replaced"), the host device receives back the same number of data packets as it sent to the cond itional access module and so synchronisation is maintained. The user-selected content is temporarily held back in a content buffer in the conditional access module so that it can be played out once the advertising content has been played.

The method described above requires that the selectable content be prepared in advance. An appropriate number of dummy packets has to be included into the selectable content such that the conditional access module can insert the same number of advertising content packets into the thus-prepared selectable content as there are dummy packets while also filtering and discarding the dummy data packets. The advertising content packets do not necessarily need to be inserted at the same place as the dummy packets before being returned to the host device, but the number of packets returned to the host must be the same as the number of packets received by the host in order to conform to the host's scheduling module. The dummy packets are therefore not necessarily directly "replaced" but rather "accounted for". Indeed, it is preferable for the dummy data packets to be either evenly distributed throughout the selectable content or distributed in any predictable manner, thereby simplifying the preparation of the selectable content. In this way the insertion of the dummy packets is simplified: for example, if advertising time is predetermined to be ten percent of the total playing time, then the preparation of the selectable content only has to take account of the fact that there should be ten percent of dummy packets somewhere in the content, preferably spaced at approximately regular intervals throughout the content. Thus, the conditional access module may buffer the non-dummy packets in a content buffer, discard the dummy packets (preferably by filtering in a way which is commonly known in the art) and prepare advertising content comprising an equal number of packets as discarded dummy packets before sending the advertising content then the buffered selected content. According to the example, for a 2-minute slot of advertising content, the conditional access module would expect to replace dummy packets from 20 minutes of the prepared selected content.

For insertion of advertising content lasting 2 minutes, as described in the above example, the buffer should preferably be sized to be at least as big as necessary to store 2 minutes of the prepared selected content. Since it may require 20 minutes worth of selected content to remove 2 minutes worth of dummy packets, the filtering of the dummy packets may be done on the fly while the advertising content is being inserted, since it is predictable that by the end of 20 minutes worth of selected content the required number of dummy data packets will be filtered out. The buffer therefore only needs to be big enough to compensate for the insertion of the advertising content and does not have to be as big as would be required to directly store all of the prepared selectable content which would be necessary to immediately filter out the equivalent number of dummy data packets as advertising content data packets to be inserted . By the time the next slot of insertion of 2 m inutes of advertising content comes around, the buffer will have cleared and the process can begin again.

The conditional access module is therefore in charge of what the user will see whenever advertising content is being sent back to the host. When the advertising content has been played, then the buffered version of the selected content is sent back to the host. The guarantee that advertising content will be played at the right time is the result of having imposed a license policy (i.e. usage rules associated with a license associated with the content). Licensing policies are known in the domain of video on demand and are usually based on the presence of a right or the time/date being within predetermined limits. According to the embodiment, the license file associated with the content may specify usage rules whereby advertising material has to be played every th irty minutes for example otherwise decryption of the selected content is not authorised. Time stamps on the selected content allow for the conditional access module to verify whether the thirty minutes has passed or not since the last advertising content was played, even if the user fast-forwarded during playing of the selected content. In this way the conditional access module can impose playing of advertising content at the appropriate time. On the other hand, once playback of advertising content has started, imposed by the conditional access module, it will be played in its entirety before the conditional access module will start returning the buffered selected content back to the host device. The conditional access module has access to the necessary keys for decrypting the encrypted user- selected content object, but will only allow the decryption key to be used if the usage rules have been met. When the user selects content to be played, the conditional access module updates the user's profile record using the characterising element associated with the selected content and compares the thus updated profile record with characterising elements associated with different pieces of advertising content in order to select the advertising content which is best targeted to the viewer. Before playing the selected content however, the conditional access module will enforce the playing of the thus- selected advertising content. The user-selected content is passed from the host to the conditional access module where at least part of the user-selected content is buffered. The selected advertising content, comprising a number of data packets, is then sent by the conditional access module to the host device. Then packets of the user-selected content are then sent from the buffer back to the host device, but not the dummy data packets. The same number of dummy data packets as the number of advertising content packets which were inserted are thereby discarded by the conditional access module. The feature whereby the number of dummy data packets is equal to the number of advertising content packets may be somewhat relaxed to the extent that any difference in these numbers should be sufficiently low so as not to generate a buffer overflow in the content buffer in the conditional access module on one hand and so as not to introduce jitter or synchronising errors during playback on the other hand. It is therefore appropriate to say that the number of dummy data packets should be approximately (or substantially) equal to the number of advertising content packets.

During playback of portions of the selected content, the user may activate the fast-forward control of the host device but at any time. The fast-forward control is registered by the host device and it has an effect on the host device, which sends content at a higher rate to the conditional access module (or sends less data to the conditional access module but at the same rate). On the other hand the fast-forward control has no effect on the conditional access module: once the advertising content has started playing, the conditional access module starts buffering any further content received from the host device and ensures that the inserted advertising content is played in its entirety before allowing the selected content to be played out from the buffer. In this manner, complete play-out of the targeted advertising content is guaranteed by the conditional access module.