WO2002071760A2

WO2002071760A2 - System for synchronizing reception of data over different networks

Info

Publication number: WO2002071760A2
Application number: PCT/GB2002/000955
Authority: WO
Inventors: Neil Cashman; Scott Walker; Walter Perotto
Original assignee: Digital Interactive Broadband Services Limited
Priority date: 2001-03-06
Filing date: 2002-03-05
Publication date: 2002-09-12
Also published as: GB0205134D0; WO2002071760A3; GB0105588D0; WO2002071760A8; AU2002236058A1; GB2377600A; GB2377600B

Abstract

A system for synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including an adaptive scheduler for determining network characteristics for the internet transmission and the audio/video broadcast transmission. The system provides synchronization triggers for respective events of the internet service at timings relative to the broadcast transmission according to the determined network characteristics. End users receive the respective events of the internet service at a known synchronization with respect to the received audio/video broadcast transmission.

Description

SYSTEM FOR SYNCHRONIZING RECEPTION OF DATA OVER DIFFERENT NETWORKS

The present invention relates to a system for synchronizing reception of data over different networks and particularly, but not exclusively, with providing for synchronized reception of material distributed over a data network such as the Internet, with material distributed over a broadcast service such as television or radio. With the development of television and computer technology, it has become possible to provide similar services through digital televisions and internet-capable devices. However, each of these mediums has its own strengths, and in particular high quality, high bandwidth audio/video content for television and feature-rich highly interactive content for internet devices. Where similar services are available over these mediums, users choose one of them dependent upon personal preference and their viewing environment at a given time.

It is well known to synchronize a television or radio broadcast of material with an Internet transmission. Typically, a user may access a web site which displays material which is relevant to a programme which is broadcast. This could be the title and performer of a music track that is being broadcast, background information about a topic being discussed in a programme, interactive content relating to the programme, and so forth. For example, WO 00/64163 describes a method for synchronizing Internet data with broadcast data. Each segment broadcast is provided with an identifier. When a segment commences, the identifier is transmitted to a database to locate data relevant to that segment. The data is then used to update a user's web browser so that the information displayed matches the segment of the programme that is being broadcast. US 6,018,7687, WO 00/07361 and WO 00/0885 also disclose systems for synchronizing web page content with a television programme that is being broadcast. Whilst existing systems synchronize the transmission of material over a broadcast service and a data network, there is a problem as regards synchronization of the reception of the material. The network characteristics for a broadcast service differ from those of the internet and the resulting differences in reception time for the end users can be a significant problem. There are even differences between broadcast services themselves and for example in the United Kingdom there is a perceptible time difference between the reception of a programme broadcast via analogue terrestrial television and digital terrestrial television. Some services are extremely time critical. For instance, for a service which provides a quiz in the form of questions and answers, it would be undesirable for answers to be received by end users via one route before the questions have been received by other end users via another route.

It is also contemplated to provide devices capable of receiving the high quality, high bandwidth audio/video content from a television network together with feature-rich highly interactive content from the internet. It is a severe disadvantage if related information received in these different ways cannot be used together in a properly synchronous manner..

It has been recognised that over the internet different material may be received at different speeds. In WO 00/13750 there is discussed the problem of loss of synchronization between streaming audio/video content and program features such as commands. The problem is solved by providing time stamps in the av stream. Commands received are held in memory and then executed when the appropriate time stamp in the a/v stream is received. WO 00/13750 provides a solution at the transmission end which enables the internal synchronization of two different types of material transmitted over the Internet. It does not provide a solution for the transmission end, where material is to be transmitted via different routes. According to the present invention there is provided a system for transmitting data to users by a plurality of routes having different transmission speeds, in which information indicative of the speed of transmission over at least one route is used to adjust the timing of transmission of data over at least one of the routes so as to synchronize the time of reception of data by users. The expression "data" includes computer data, audio, video and so forth.

Thus, for example, a particular user may receive audio / video content in a digital broadcast via a terrestrial, cable or satellite transmission. The user may also receive interactive content in the form of data transmitted over the internet. This interactive content may be combined with the audio / video content on a single display or may be displayed on a computer monitor whilst the audio / video content is displayed on a television. Alternatively, one user may receive a television broadcast via a terrestrial, cable or satellite transmission, whilst another user may receive a corresponding webcast displayed on a computer monitor. The expression "transmission speed" encompasses all reasons for any difference in timing of reception of data via different routes. It is not restricted to delays caused by differences in the networks as such, and also encompasses, for example, delays caused by initial processing of data such as reformatting of conventional audio / video information into a web format

In a preferred arrangement, an adaptive scheduler is provided for determining the network characteristics of at least one route and for dynamically adjusting the timing of transmission of data over at least one of the routes so as to synchronize the time of reception of data.

The system in accordance with the invention is of particular use for synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, and may include: an adaptive scheduler for determining network characteristics for the internet transmission and the audio/video broadcast transmission; an internet trigger provider for providing synchronization triggers for respective events in the internet service; and a controller, responsive to timing of the audio/video broadcast transmission, for controlling the internet trigger provider according to the determined network characteristics such that end users receive the respective events in the internet service at a known synchronization with the audio/video broadcast transmission.

By determining the network characteristics for the internet transmission and the audio/video broadcast transmission, it is possible to judge the relative transmission delays for data sent via the internet transmission and via the audio/video broadcast transmission. In this way, the controller can control the relative timings of the internet service events and the audio/video stream as received by the end users. As will become clear below, in some circumstances, it may be important for the internet service events to be received by the end user at a particular place in the audio/video stream. However, in other cases, the actual relative timing between the internet service events and the audio/video stream as received by the end users may be of less importance. However, since the relative timing of the internet service events and the audio/video stream as received by the end users is known, it becomes possible to ensure that other parts of the audio/video broadcast transmission, such as interactive television services, can be synchronized with reception of the internet service events. The internet service may be provided simultaneously in different internet transmissions provided by respective internet service providers.

In this case, preferably, the adaptive scheduler determines the network characteristics for each internet transmission provided by its respective internet service provider and the controller controls the internet trigger provider to provide different synchronization triggers for the respective internet transmissions according to the respective network characteristics.

In this way, irrespective of the internet service provider used, all end users may receive the internet service events at a timing relative to the audio/video stream as required by the broadcast/service provider. Preferably, the system further includes a web server responsive to the synchronization triggers from the internet trigger provider to provide the respective events over the internet.

Of course, following on from above, a plurality of web servers may be provided, each with its own synchronization triggers. Preferably, a controllable variable delay is provided for delaying the audio/video stream provided for the audio/video broadcast transmission.

In this way, it is possible to control the timing of the audio/video stream in the broadcast, such that the timing with which end users receive the audio/video stream is also controlled. Preferably, a webcast reformatter is provided for reformatting the audio/video stream for transmission over the internet wherein the adaptive scheduler determines the performance characteristics of the webcast reformatter and the controller controls the variable delay according to the performance characteristics and the network characteristics such that end users receive the audio/video stream by the internet transmission and the audio/video broadcast transmission at the same time. It will be appreciated that the processing required to reformat the audio/video stream takes time such that inclusion of the audio/video stream in the internet transmission is delayed. By determining the performance characteristics of the webcast reformatter and, hence, the delay time introduced, the controller can control the variable delay to provide an appropriate delay for the audio/video stream introduced in the audio/video broadcast transmission.

The audio/video stream may be provided in different audio/video broadcast transmissions over respective networks.

In this case, the adaptive scheduler preferably determines the network characteristics for each network and the controller controls the variable delay to delay the audio/video stream provided for the different audio/video broadcast transmissions by different respective amounts according to the respective network characteristics.

Thus, where the transmission time is different for different networks, it is possible for the controller to delay the audio/video stream in the faster networks such that all end users receive the audio/video stream at the same time irrespective of the network which they are using.

The controller may control the variable delay at the same time to ensure that the audio/video stream is received from the television networks at the same time as via the internet transmission. A number of ISPs are contacted via the ping procedure, and an average value is assumed for the delay over the Internet. In this way, effective simultaneous reception of the web cast transmission of the audio/video stream can be provided even though different ISPs introduce different delays.

Preferably, a television trigger provider is used for providing synchronization triggers for respective events in a television service in the audio/video broadcast transmission, wherein the controller controls the internet trigger provider and the television trigger provider according to the network characteristics such that end users receive corresponding events of the internet service and the television service in synchronism.

Thus, by determining the network characteristics for the audio/video broadcast transmission by which the television service is provided and the internet transmission by which the internet service is provided, the controller can determine the relative timings at which an end user would receive these services. Hence, the controller can control triggering of the television service event and the internet service events such that they occur with the same timing for the end users.

In this case, although the relative timing to the audio/video stream is known, it may not be of significant importance and, indeed, may be allowed to wander.

The television service may be provided in different respective audio/video broadcast transmissions over respective networks. Hence, when the audio/video stream is provided over different television networks, the corresponding television services are provided also. In this case, the controller may control the television trigger provider to provide different synchronization triggers for the respective networks according to the respective network characteristics.

Thus, corresponding television service events of different broadcast networks may all be provided to an end user in synchronism with corresponding internet service events. Indeed, in the manner discussed above, the internet service events may be provided in synchronization irrespective of the internet service provider.

Furthermore, where necessary, the audio/video stream may be provided to all users in synchronism irrespective of the broadcast network and in synchronism with the television service and internet service events. Where there are no corresponding internet service events of interest, it is also possible for the controller merely to synchronize the television service events provided over different broadcast networks.

The system may include broadcast play out equipment for providing, for transmission in the audio/video broadcast transmission, a television service and triggers corresponding to said synchronization triggers from said television trigger provider. Hence, where, for instance, television services are provided by way of a data carousel, data for the television services is pre-loaded from the data carousel to the end users television device and then a trigger is broadcast so as to actuate a particular event in the television device. Preferably the television service events include at least one of scenes, modules and television format resources and pictures.

A complete list of events is not possible. An event occurs in an interactive application when the application is required to do something at a certain point in time during the AV broadcast. A non-exhaustive list of events could be: quiz show questions, vote requests, interactive adverts, dynamic icons, animations, etc. For the same AN content, the events will be the same on the TV and on the Internet; the actual format and delivery method will be different.

Preferably, the internet service events include at least one of HTML and Java script files, other web scripting technologies and servlets and Web format resources and pictures.

Preferably, the audio/video stream comprises a transport stream containing at least one of live and pre-recorded audio/video data.

Preferably, a schedule editor is provided having a user interface by which a user can select the desired synchronization. The schedule editor creates and edit the schedule. Basically it allows to specify what should happen when, and enter schedule details.

It should be appreciated that at least some aspects of the invention can also be embodied in software and, hence, can be provided as code components on a computer readable storage medium. The invention may be viewed from other aspects. From one aspect there is provided a method of transmitting data to users by a plurality of routes having different transmission speeds, in which information indicative of the speed of transmission over at least one route is used to adjust the timing of transmission of data over at least one of the routes so as to synchronize the time of reception of data by users. From another aspect, there is provided a method of synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including: determining network characteristics for the internet transmission and the audio/video broadcast transmission; receiving a timing of a broadcast stream to be broadcast in the audio/video broadcast transmission; and providing synchronization triggers for respective events of the internet service at timings relative to the broadcast stream according to the determined network characteristics such that end users receive the respective events of the internet service at a known synchronization with the audio/video stream as received in the audio/video broadcast transmission.

From a still further aspect there is also provided an system for synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including: an adaptive scheduler for determining network characteristics for the internet transmission and the audio/video broadcast transmission; an internet trigger provider for providing synchronization triggers for respective events in the internet service; and a controller, responsive to timing of an audio/video stream to be broadcast in the audio/video broadcast transmission, for controlling the internet trigger provider according to the determined network characteristics such that end users receive the respective events in the internet service at a known synchronization with the audio/video stream as received in the audio/video broadcast transmission.

From another aspect there is provided a system for synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including: an adaptive scheduler for determining network characteristics for the internet transmission and the audio/video broadcast transmission; an internet trigger provider for providing synchronization triggers for respective events in the internet service; and a controller, responsive to timing of the audio/video broadcast transmission, for controlling the internet trigger provider according to the determined network characteristics such that end users receive the respective events in the internet service at a known synchronization with the audio/video broadcast transmission. An embodiment of the present invention will be more clearly understood from the following description of an embodiment, given by way of example only, with reference to the accompanying drawings, in which:

Figure 1 illustrates schematically a transmission system embodying the present invention; and Figure 2 illustrates a flow diagram for the process of synchronization.

An audio/video data stream may be provided from a variety of sources. Hence, as illustrated in Figure 1, the audio/video content 2 may come from live broadcast equipment 4 and/or pre-recorded sources 6. This audio/video content is encoded by the encoder 8 so as to form the audio/video data stream 10. The encoded audio/video data stream may be of any known type such as an MPEG transport stream.

Television content 12 in the form of television services, such as interactive applications, may also be provided. This content may include scenes or modules 14 and resources and pictures 16 for a TV platform. The TV content 12 is output by broadcast play-out equipment 18 as a television service 20. The broadcast play-out equipment 18 might typically include a data carousel. However, it could also be implemented with delivery from on-demand servers. Although the delivery method of these servers is similar to the one used on the Internet, data travels on a dedicated network and delay conditions are very different and well known. The audio/video data stream 10 is combined at 11 with the television service

20 and then provided to one or more providers 21 of an audio/video broadcast transmission for reception by a user's television 100.. The audio/video broadcast transmission may be of any known type including satellite, terrestrial and cable transmissions. Furthermore, the audio/video data stream 10 and television service 20 may be provided simultaneously to a number of different providers for different audio/video broadcast transmission. In addition, each broadcast provider may receive a number of different audio/video data streams 10 and television services 20. Service providers may wish additionally to provide internet services available to users over the internet. In this respect, the web content 22 for the internet service may include HTML or Java script 24 and resources and pictures 26 of a web format. A web server 28 provides this web content 22 as an internet service 30 to be made available to end users over the internet 32, for viewing on a terminal 200 using conventional browser technology, if desired.

The audio/video content 2, the TV content 12 and the web content 22 may all be developed separately with no intention for them to inter-relate. However, usually, the intention of a. service provider will be for the television service 20 to relate to the corresponding audio/video data stream 10. It is also considered now that the service provider may wish to provide a corresponding internet service 30. The internet service 30 might be provided merely to provide services corresponding to the television service 20, but over an alternative transmission path. Alternatively, the internet service might contain entirely different services or overlapping services to supplement the television service 20.

Irrespective of the particular content of the television service 20 and internet service 30, in some circumstances, it will be desirable for the content of those services to be synchronized in some way with relation to each other and/or the audio/video data stream 10. For instance, during the broadcast of a quiz show, corresponding television and internet services may transmit related questions and answers. In this case, a service provider would wish end users to receive the questions and answers with a predetermined timing with regard to the television show. Furthermore, the service providers would wish end users to receive the questions and answers at the same time irrespective of whether this is via the television network or the internet.

As illustrated in Figure 1, a broadcast synchronization controller 40 is provided to synchronize reception of the audio/video, television and web content by the end users. The synchronization control 40 is provided with an adaptive scheduler 42 for providing the network characteristics of the broadcast transmission networks over which the audio/video data stream 10 and the television service 20 are to be broadcast. In this way, the broadcast synchronization controller 40 is able to determine the approximate delay between providing the audio/video data stream 10 and reception of that audio/video data stream by the end users. The adaptive scheduler 42 also determines from the web server 28 the network characteristics for providing an internet service 30 over the internet 32 to an end user. In this respect, it should be understood that different internet service providers may introduce different delays and, hence, the same internet service 30 provided by different internet service providers may take different times to reach the end users. The adaptive scheduler 42 works with the web server 28 to determine these delays.

The ping procedure consists in sending a few byte packets to a server, which then returns them. The machine which sent the packets can then work out the transmission delay by calculating the difference between transmission and reception times. The same procedure can be improved by making every server in the way between the originating machine and the destination one to send packets in return. This allows a complete analysis of the delays on the various branches of the network. The invention will use the ping procedure to calculate delays to key servers of known ISPs covering the region/market desired for the service in question. The scheduler requests the procedure and uses the results to calculate the average delays, but the ping procedure is actually operated by the web server because it is connected to the Internet.

Thus, the broadcast synchronization controller 40 can determine the relative delays for audio / video data sent over the broadcast transmission network and internet service data sent via the internet.

As illustrated, a content play-out scheduler 44 is provided. This provides synchronization data with regard to the audio/video data stream 10. The play out scheduler generates signals to initiate the transmission of AV and data objects. A live trigger input 45 enables manual, non-predetermined triggers to be taken by the system. By means of the synchronization data for the source audio/video data stream 10 and knowledge of the delays over the broadcast transmission networks and the internet, the broadcast synchronization controller 40 is then able to provide synchronization triggers 46 to the web server 28. The web server 28 responds to the synchronization triggers 46 to enable respective internet services or events within those services at the user end. In this respect, the web server 28 might provide an internet service on the internet at the time it receives the synchronization trigger 46. Alternatively, end users may have already downloaded the basic internet service 30 from the web server 28, but await some activation signal for the service or particular events within the service. Thus, in response to the synchronization triggers 46, the web server 28 may providing corresponding internet triggers to the end users over the internet 32.

In this way, the broadcast synchronization controller 40 is able to ensure that internet services become available to end users with a known timing relative to the audio/video data stream 10.

The television services 20 which are combined with the audio/video data stream to be provided to end users over the broadcast transmission networks, of course suffer the same delays as those determined by the network characteristics for the audio/video broadcast transmission. Typically, however, the television services 20 are available on a data carousel and will have already been downloaded by the end user's equipment. Events of the television services are then initiated by triggers which are broadcast in the broadcast stream. Hence, the broadcast synchronization controller 40 also provides synchronization triggers 48 to the broadcast play-out equipment 18. In response to the synchronization triggers 48, the broadcast play-out equipment 18 transmits an equivalent trigger in the broadcast stream. Thus, knowing the delays occurring on the broadcast transmission networks and the internet, the broadcast synchronization controller 40 is able to issue synchronization triggers 46 to the web server 28 and synchronization triggers 48 to the broadcast play-out equipment 48 such that the triggering of events in the internet service 30 can be synchronized at the end users with events in the television service 20. In other words, where an internet service is intended to mimic a television service, corresponding events of the two services can be caused to take place at the same time. Alternatively, where an internet service is intended to supplement a television service, various events of the two services can be coordinated and synchronized to occur with a predetermined relative timing. It will be appreciated that, in some circumstances, the relative timing of the television and internet services with the audio/video data stream is not of significant importance. As described above, the broadcast synchronization controller 40 is able to synchronize the internet service with the television service of the audio/video broadcast transmission and/or the audio/video data stream of the audio/video broadcast transmission.

In some circumstances, it may be desired to transmit the audio/video data over the internet 32. In this regard, a web cast reformatter 50 is provided. The web cast reformatter reformats the audio/video data stream 10 to provide web cast data 52 which is combined at 31 with the internet service 30 for transmission over the internet 32.

Due to the processing time required to reformat the audio/video data for web cast, the web cast data 52 is delayed with respect to the audio/video data stream 10.

Clearly, it is desirable for end users to receive audio/video data simultaneously via broadcast transmission and the internet. In particular, during broadcast of a live transmission, it would be undesirable for users to receive the same program with different timings. In order to allow for compensation in this regard, a variable delay 54 is provided for delaying the audio/video data stream 10 by a variable amount before being passed to the broadcast transmission network.

The adaptive scheduler 42 provides the performance characteristics of the web cast formatter 50 to the broadcast synchronization controller 40. By taking account of the delays occurring due to the web cast reformatter 50, internet transmission and audio/video broadcast transmission, the broadcast synchronization controller 40 is then able to control the variable delay 54 so as to introduce an appropriate delay to synchronize reception by the end users of the audio/video data via the audio/video broadcast transmission and the internet transmission. It will be appreciated that the same audio/video data stream 10 may be provided to different broadcast networks. In this case, it is possible to provide different delays to the audio/video data destined for the various broadcast networks. It thus becomes possible for the broadcast synchronization controller 40 to ensure that end users receiving audio/video data from different networks receive the same audio/video data in synchronism.

As illustrated, a schedule editor 60 is also provided. This creates and edits the schedule and is used to specify what should happen when, and enter schedule details. The process of synchronization will be described with reference to Figure 2, which sets out the steps of the adaptive scheduling algorithm used by scheduler 42..

In step 100, the system, namely the broadcast synchronization controller 40 and related components, is synchronized with the station clock, namely the clock controlling the audio/video data stream 10. In step 102, the delay incurred to the audio/video content by the web cast reformatter 50 is determined. The web cast reformatter 50 may apply a number of different formats such as QuickTime and Real. These are encoding formats for AV to be delivered over the Internet.

The delay introduced by the web cast reformatter 50 is dynamic. In other words, it will vary continuously according to the particular audio/video data requiring reformatting. The resulting delay times may be monitored and used continuously by the broadcast synchronization controller 40.

In step 104, the various broadcast network delay characteristics are determined. Different networks, such as Sky Digital, On Digital, etc will introduce different delays.

Details about broadcast networks are pre-loaded in the system. Broadcasters govern TV networks structures and their characteristics can be known in advance. Contrarily, the Internet structure is not designed by anybody in particular and needs the method proposed by this invention to work out the delays. In step 106, the delay characteristics of the internet for a variety of connection types, such as 56k modem, ISDN, ADSL, etc, are determined. These delay times may be determined by the system itself by using .a "Ping" procedure described above to test PCs connected through various internet service providers using these connections.

In step 108, the necessary synchronization information for the trigger events and the television delay is calculated. This is achieved by taking account of the various characteristics determined in the previous steps.

In step 110, the television service triggers, such as interactive content triggers are transmitted. Indeed, different triggers may be sent for the different APIs available, e.g. OpenTV, Liberate, MediaHighway. In step 112, internet triggers are sent, for instance WWW interactive content triggers. Indeed, various different triggers may be sent for the various different connection speeds being targeted.

In step 114, the various delay values for the TV broadcast streams, such as Sky Digital, Telewest, On Digital, etc, are provided to the delay so as to ensure that the TV content arrives in sync with the internet content.

The variable delay concerns the AV. Triggers can get the same delay by having the broadcast equipment delivering them at the right time.

Finally, in step 116, it is determined whether or not to continue the dynamic synchronization. It should be appreciated that the steps illustrated in Figure 2 are schematic and that many of these steps will occur simultaneously.

Claims

1. A system for transmitting data to users by a plurality of routes having different transmission speeds, in which information indicative of the speed of transmission over at least one route is used to adjust the timing of transmission of data over at least one of the routes so as to synchronize the time of reception of data by users.

2. A system as claimed in claim 1, in which an adaptive scheduler is provided for determining the network characteristics of at least one route and for dynamically adjusting the timing of transmission of data over at least one of the routes so as to synchronize the time of reception of data.

3. A system as claimed in claim 1 or 2 which is adapted for synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission.

4. A system as claimed in claim 1 which is adapted for synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including: an adaptive scheduler for determining network characteristics for the internet transmission and the audio/video broadcast transmission; an internet trigger provider for providing synchronization triggers for respective events in the internet service; and a controller, responsive to timing of the audio/video broadcast transmission, for controlling the internet trigger provider according to the determined network characteristics such that end users receive the respective events in the internet service at a known synchronization with the audio/video broadcast transmission.

5. An system as claimed in claim 4, wherein: the internet service is provided in different internet transmissions from respective internet service providers; the adaptive scheduler determines the network characteristics for each internet transmission provided by the respective internet service provider; and the controller controls the internet trigger provider to provide different synchronization triggers for the respective internet transmissions according to the respective network characteristics.

6. An system as claimed in claim 4 or 5 further including: a web server responsive to said synchronization triggers from said internet trigger provider to provide the respective events over the internet.

7. An system as claimed in claim 4, 5 or 6 further including: a controllable variable delay for delaying an audio/video stream provided for the audio/video broadcast transmission.

8. An system as claimed in claim 7 including: a webcast reformatter for reformatting the audio/video stream for transmission over the internet wherein the adaptive scheduler determines the performance characteristics of the webcast reformatter and the controller controls the variable delay according to the performance characteristics and the network characteristics such that end users receive the audio/video stream in synchronism by internet transmission and audio/video broadcast transmission.

9. An system as claimed in claim 7 or 8 wherein: the audio/video stream is provided in different audio/video broadcast transmissions over respective networks; the adaptive scheduler determines the network characteristics for each network; and the controller controls the variable delay to delay the audio/video stream provided for the different audio/video broadcast transmissions by different amounts according to the respective network characteristics.

10. An system as claimed in any of claims 4 to 5 further including: a television trigger provider for providing synchronization triggers for respective events in a television service in the audio/video broadcast transmission; wherein the controller controls the internet trigger provider and the television trigger provider according to the network characteristics such that end users receive corresponding events of the internet service and the television service in synchronism.

11. An system as claimed in claim 10 wherein: the television service is provided in different respective audio/video broadcast transmissions over respective networks; and the controller controls the television trigger provider to provide different synchronization triggers for the respective networks according to the respective network characteristics.

12. An system as claimed in claim 10 or 11 further including: broadcast play-out equipment for providing, for transmission in the audio/video broadcast transmission, a television service and triggers corresponding to said synchronization triggers from said television trigger provider.

13. An system as claimed in claim 10, 11 or 12 wherein: the television service events include at least one of scenes, modules and television format resources and pictures.

14. An system as claimed in any of claims 4 to 13 wherein: the internet service events include at least one of HTML and Java script files, other web scripting technologies and servlets and web format resources and pictures.

15. An system as claimed in any of claims 4 to 14 wherein the audio/video stream comprises a transport stream containing at least one of live and pre-recorded audio/video data.

16. An system as claimed in any of claims 4 to 15 further including: a schedule editor having a user interface by which a user can select the desired synchronization.

17. A method of transmitting data to users by a plurality of routes having different transmission speeds, in which information indicative of the speed of transmission over at least one route is used to adjust the timing of transmission of data over at least one of the routes so as to synchronize the time of reception of data by users.

18. A method of synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including: determining network characteristics for the internet transmission and the audio/video broadcast transmission; receiving a timing of a broadcast stream to be broadcast in the audio/video broadcast transmission; and providing synchronization triggers for respective events of the internet service at timings relative to the broadcast stream according to the determined network characteristics such that end users receive the respective events of the internet service at a known synchronization with the audio/video stream as received in the audio/video broadcast transmission.

19. A system for synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including: an adaptive scheduler for determining network characteristics for the internet transmission and the audio/video broadcast transmission; an internet trigger provider for providing synchronization triggers for respective events in the internet service; and a controller, responsive to timing of an audio/video stream to be broadcast in the audio/video broadcast transmission, for controlling the internet trigger provider according to the determined network characteristics such that end users receive the respective events in the internet service at a known synchronization with the audio/video stream as received in the audio/video broadcast transmission.

20. A method of synchronizing reception of an internet service in an internet transmission with an audio/video broadcast transmission, including: detemiining network characteristics for the internet transmission and the audio/video broadcast transmission; receiving a timing of the audio/video broadcast transmission; and providing synchronization triggers for respective events of the internet service at timings relative to the audio/video broadcast transmission according to the determined network characteristics such that end users receive the respective events of the internet service at a known synchronization with respect to the received audio/video broadcast transmission.

21. A computer readable storage medium having recorded thereon code components that, when loaded on data processing means and executed will cause the data processing means to operate according to any one of the preceding claims.