Method for broadcasting a series of contents from a source to receiver terminals, through a computer network, related signal, broadcasting source and terminal

Abstract

A method of broadcasting a succession of contents through a computer network from a broadcasting source (S) to a plurality of receiver terminals able to receive from the source. The method includes, for each content, sending data units conveying the content from the source through the computer network, and supplying the receiver terminals with an indication enabling them to identify each transition between two successive contents, thus enabling the receiver terminals to determine the time of a transition between successive contents more precisely. The data units to be broadcast are marked by modifying the marking of the data units of the successive contents separated by a single transition. The receiver terminals (T) are supplied with marking information enabling them to distinguish between data units belonging to different contents (Cn, Cn+1) with the aid of their marking.

Description

The invention relates to a method of broadcasting a succession of contents from a broadcasting source to a plurality of receiver terminals through a computer network, such as the Internet in particular, and further relates to a broadcasting source and a receiver terminal suitable for implementing the method.

Certain television stations broadcast a succession of contents such as television shows, films, and other programs in real time on the Internet from a broadcasting source S. The broadcasting mode used most often is the multicast mode, enabling the source S to broadcast each content to a plurality of receiver terminals in a single sending. The source S sends units of data conveying the content to be broadcast, in this instance IP data packets also known as IP datagrams. These packets are duplicated in cascade by routers situated at nodes of the network in order to be routed to the various receiver terminals. To receive a content, each terminal first recovers a session description protocol (SDP) file associated with the source S, for example by downloading it from an access portal via the Internet. The structure of the SDP file is defined by the Internet Engineering Task Force (IETF) and is described in the document RFC 2327. The file conveys the information required to enable the receiver terminals to begin to receive contents broadcast by the source S. A main SDP file contains all the information required to begin to receive from the source S, regardless of the content that is being broadcast. Other SDP files, specific to the contents (TV show, film, conference, etc.) broadcast by the source S, contain only the information necessary for receiving those particular contents. To receive a content broadcast by the source S, a terminal sends a request to acquire that content to the source via the Internet using the Internet Group Management Protocol (IGMP). The first Internet router to receive this request when it is already receiving IP data packets sent by the source S duplicates the IP data packets and routes them either to the terminal or to another router closer to the terminal.

The various contents broadcast successively by the source S have configuration characteristics that may vary from one content to another (resolution, frequency, 4/3 or 16/9 format, coding, for example MPEG4, MPEG2, audio in different languages, scrambling, or other parameters). To take account of such changes, the receiver terminals must be able to identify transitions between successive contents. To this end, it is known in the art, in particular in the field of MPEG2 satellite or cable television broadcasting, to communicate to the receiver terminals a temporal indication of the time at which the transition is scheduled. However, that solution is not totally satisfactory, for the following reasons: firstly, the temporal indication of the time of the transition is usually inaccurate and, secondly, that solution necessitates knowing the time of the transition accurately in advance, which may prove extremely difficult, if not impossible, in certain circumstances. Examples of such circumstances that may be cited are unscheduled interruptions of programs in order to broadcast a newsflash and live coverage of a tennis match, whose duration cannot be known in advance.

The technical problem addressed by the invention is therefore that of proposing a method of broadcasting a succession of contents through a computer network from a broadcasting source S to a plurality of receiver terminals, the method comprising the steps of:

• • for each content, sending data units conveying said content from the source through the computer network, and
  • supplying the receiver terminals with an indication enabling them to identify each transition between two successive contents, thus enabling the receiver terminals to determine the time of a transition between successive contents more precisely.

The problem addressed by the invention is solved by the fact that the method further comprises the following steps:

• • marking (40b) the data units to be broadcast by modifying the marking of the data units of the successive contents separated by a single transition, and

supplying to the receiver terminals (T) marking information enabling them to distinguish between data units belonging to different contents (C_n, C_n+1) with the aid of their marking.

Marking the data units enables the receiver terminals to identify transitions between successive contents in real time and with all the necessary accuracy. The terminals do not need to know the precise time of the transition to take account of changes between two successive contents separated by a transition. It is sufficient for them to have the marking information that enables them to distinguish between data units belonging to the two contents as a function of their marking, in other words that enables them to determine the content to which each data unit belongs from its marking.

It is advantageous if the data units of a content are broadcast on a broadcasting channel and the marking information relating to said content is broadcast on a signaling channel separate from the broadcasting channel. Thus the successive contents and the marking information relating to the contents are broadcast independently of each other on two separate channels.

In this case, the marking information relating to a given content is preferably inserted into enabling data relating to said content.

The enabling data relating to a content is broadcast on the signaling channel and contains the configuration characteristics of the content which enable the content to be used.

The marking information relating to a content is preferably sent during the broadcasting of a preceding content. The marking information relating to a content C_n+1 is generally sent to the receiver terminals a first time during the broadcasting of the preceding content C_n, unless its duration is insufficient. In this case, to alert the receiver terminals sufficiently far ahead of the scheduled time of the transition, the marking information relating to the content C_n+1 is sent the first time while broadcasting a content prior to C_n. However, it is not necessary to know the precise time of the transition, merely a time period during which the transition is scheduled.

In one particular embodiment of the invention, the broadcasting time remaining before said transition is evaluated and the marking information relating to the content following said transmission is transmitted when the remaining broadcasting time is below a predefined time threshold. The time remaining before the transition is determined approximately and the marking information is transmitted when this remaining time falls below the threshold.

In another embodiment, the marking information relating to the content after said transition is sent regularly throughout the broadcasting of the content preceding said transition. Thus it is no longer necessary to monitor the remaining broadcasting time of the current content.

The invention also provides a signal conveying a succession of contents segmented into data units which is characterized in that the data units belonging to different contents have respective different markings.

The invention further proposes a broadcasting source adapted to broadcast a signal as defined above through a computer network and a receiver terminal adapted to receive a signal as defined above through a computer network.

The invention will be better understood with the aid of the following description of one particular embodiment of the broadcasting method of the invention and particular embodiments of the broadcasting server and the terminal of the invention, which description is given with reference to the appended drawings, in which:

FIG. 1 is a diagram showing a broadcasting source, broadcast channels, a signaling channel, a portal, a receiver terminal, and the Internet;

FIG. 2 is a functional block diagram of the broadcasting source from FIG. 1;

FIG. 3 is a functional block diagram of the receiver terminal from FIG. 1;

FIGS. 4 a and 4b show data units and enabling data units broadcast by the FIG. 1 source in two different broadcasting modes;

FIGS. 5 a and 5b show two data packets marked at the level of the SL layer and at the level of the Flexmux layer, respectively; and

FIGS. 6 to 14 are flowcharts showing steps of a broadcasting method of the particular embodiment of the invention described here.

FIG. 1 shows a broadcasting source S, a receiver terminal T, a TV portal P, and a computer network, in this instance the Internet.

In the particular example of the present description, the source S is a television channel, referred to hereinafter as channel A, hosted by an Internet audiovisual server and broadcasting a succession of contents (television shows, films, advertisements, etc.) in multicast mode to the receiver terminals T via the Internet. Referring to FIG. 2, the source S comprises a database 10, a broadcasting control module 11, a marking module 12, a segmentation module 13, two sending modules 14 and 15, and an Internet connection interface 16.

The database 10 is fed by a programming centre, not shown, and contains contents C_n to be broadcast and associated enabling data DE for each content C_n. By definition, the enabling data DE relating to a content C_n consists of data enabling a receiver terminal T to read that content. In this instance, the enabling data DE relating to the content C_n contains:

i) information necessary for receiving one or more broadcast channels CD_x on which the content C_n is broadcast, namely the multicast Internet address of each of the broadcast channels CD_x, the transmission mode used (synchronization layer, multiplexing), and the various broadcast data streams (audio, video, etc.), with the names of the ports sending those streams, and

ii) configuration characteristics of the content C_n that are necessary for the receiver terminals to decode the content C_n correctly (resolution, frequency, format, coding, language, and scrambling characteristics).

The control module 11 controls the broadcasting of the contents and the corresponding enabling data via the Internet.

The segmentation module 13 is connected to the control module 11 and to the two sending modules 14, 15 and is adapted to segment the contents and the enabling data into data units, in this instance into Internet Protocol (IP) data packets, to be broadcast on the Internet.

The two sending modules 14, 15 are connected to the Internet connection interface 16. To broadcast a content, the module 14 sends a signal conveying the content in multistream mode on broadcast channels CD_x. In parallel with this, the module 15 regularly sends the enabling data of the content on a signaling channel CS. The multistream broadcast mode consists in sending, for each type of data (audio, video, etc.), a basic data stream and one or more complementary data streams intended to enhance the quality of the signal conveyed by the basic stream. Each receiver terminal may thus adapt the quality of the signal received to its own capabilities, using the basic stream and where appropriate one or more of the complementary streams. The source S segments each stream into IP data packets and sends the IP packets via the Internet on a broadcast channel CD_x. FIG. 4b shows part of the basic video stream and the basic audio stream, segmented into video IP data packets P_IPV_x and audio IP data packets P_IPA_x, respectively, of three contents C₀₁, C₀₂, C₀₃ broadcast successively by the source S. The arrow indicates the direction of flow of the data. Thus data on the right-hand side in the figure is sent by the source S before data on the left-hand side. In parallel with this, as may also be seen in FIG. 4, while broadcasting each content, the source S regularly sends the enabling data DE of that content. Also, the source S sends the enabling data for the content following the transition via the signaling channel CS at least once before each transition between two successive contents.

The marking module 12 comprises a marking control unit 120 and two insertion units 121, 122. The insertion unit 121 is between the segmentation module 13 and the sending module 14 and the insertion unit 122 is between the control module 11 and the segmentation module 13. The control unit 120 assigns each content to be broadcast a marking indicator and controls the operation of the two insertion units 121, 122. In the particular example of this description, the marking indicators are assigned modulo 256. In other words, the marking indicators respectively assigned to the successive contents are successive numbers from a set of numbers ranging from 0 to 255, the marking indicator of a content being one more than the marking indicator of the preceding content unless said content is equal to 255, in which case the marking indicator of the next content is equal to 0. Sequentially and cyclically assigning successive contents marking indicators from a set of limited size separates contents carrying the same marking indicator by a sufficiently long time interval to prevent confusion between those contents in the receiver terminals T without it being necessary to use an excessively high number of different marking indicators. During the broadcasting of a content C_n, the insertion unit 121 marks all the IP data packets of that content C_n by inserting therein the marking indicator assigned to that content C_n, in a header of a protocol layer, in this instance the synchronization layer (SL). The synchronization layer is an application layer. FIG. 5a shows a video data packet at the level of the synchronization layer, comprising the SL header, the number assigned to the content concerned, i.e. the marking indicator, and the video data of that content. The marking indicator could equally be inserted at the level of the Flexmux layer, which is below the synchronization layer, as shown in FIG. 5b. The marking indicator enables the receiver terminals T to identify the content C_n to which the IP data packet belongs. The role of the marking indicators is generally to enable the receiver terminals T to distinguish between IP data packets that belong to different contents, as a function of the content to which they belong, and thereby to mark transitions between successive contents. In parallel with this, the insertion unit 122 inserts into the enabling data relating to the content C_n the marking indicator assigned to that content C_n, as explained later.

Referring to FIG. 3, the terminal T comprises a man-machine interface 20 comprising a display screen, input means (here a keyboard and a device for selecting and moving a cursor on the screen), a loudspeaker, an Internet browser 21, an Internet connection module 22, an operation module 23, and a central control unit, not shown.

The operation module 23 enables the terminal T to receive and use, i.e. to read, contents that are broadcast via the Internet by various broadcasting sources, and in particular by the source S. It comprises a memory 230 for storing an SDP descriptive file relating to a broadcasting source, a unit 231 for receiving broadcast channels CD_x from the source, a unit 232 for receiving a signaling channel CS from the source, a unit 233 for recording enabling data in a memory 234, and a decoding unit 235. The two receiving units 231 and 232 are connected to the Internet connection module 22. The decoding unit 235 is connected to the memory 234, to the receiving unit 231, and to the man-machine interface module 20.

The receiving unit 232, which is connected to the memory 230, is adapted to receive the signaling channel CS with the aid of information contained in the SDP file stored in the memory 230 and to receive the enabling data broadcast via the signaling channel CS. The recording unit 233, which is between the receiving unit 232 and the memory 234, is adapted to store in the memory 234 enabling data received by the unit 232 via the signaling channel CS. The memory 234 therefore contains, for each content C_n broadcast by the source S, information necessary for receiving the content C_n, the configuration characteristics of the content C_n, and the associated marking indicator, which is assigned to the content C_n by the source S. The receiving unit 231, which is connected to the memory 234, is adapted, with the aid of enabling data stored in the memory 234, to receive the broadcast channels CD_x and thus to receive contents broadcast via the broadcast channels CD_x.

The operating module 23 further comprises a detection unit 236 between the receiving unit 231 and the decoding unit 235. The detection unit 236 is adapted to detect the marking indicator inserted into each IP data packet received via a broadcasting channel CD_x and to supply it to the decoding unit 235. On reception of a content via the broadcast channels CD_x, the detection unit 236 detects the marking indicator inserted into the received IP packets conveying that content and supplies it to the decoding unit 235, which unit looks in the memory 234 for enabling data associated with that marking indicator, which is that for the received content, extracts the configuration characteristics therefrom, and, using those characteristics, decodes the received IP packets for local broadcasting of the content via the man-machine interface 20.

The TV portal P is an Internet television website which offers a TV guide and hypertext links to TV channels. The portal P contains in particular the programs of channel A.

The method of broadcasting a succession of contents from a broadcasting source S to a plurality of receiver terminals T via the Internet is described next.

Referring to FIG. 4, the source S broadcasts in multicast mode and in multistream mode over the broadcast channels CD_x a signal conveying a succession of contents segmented into marked IP data packets and, in parallel with this, regularly sends enabling data for the content being broadcast on the signaling channel CS. The source S assigns sequential marking indicators to the successive contents in order to modify the marking of the IP data packets of successive contents separated by a single transition. Consequently, the IP packets relating to two successive contents separated by a single transition contain respective different marking indicators.

FIGS. 10 to 13 depict the operation of the source S when broadcasting two successive contents C_n and C_n+1. In a step 40, the source S broadcasts the content C_n via the broadcast channels CD_x. For this purpose, the source S segments the content C_n into IP packets in a step 40a, inserts the marking indicator assigned to the content C_n into the header of the IP packet at the level of the SL protocol layer in a step 40b, and then sends the marked IP packets over the Internet via the channels CD_x in a step 40c. In parallel with the step 40, the source S broadcasts enabling data DE for the content C_n via the signaling channel CS in a step 41. For this purpose, the source S inserts the marking indicator assigned to the content C_n into the enabling data DE of the content C_n in a step 41a, segments this enabling data DE into IP packets in a step 41b, and then sends the IP packets over the Internet via the channel CS in a step 41c. In a step 42, once it has sent the enabling data DE for the content C_n, the source S verifies if the transition between the content C_n and the content C_n+1 has occurred. The step 41 of sending the enabling data DE for the content C_n is repeated with a period T until the transition occurs. Immediately the transition has occurred, step 41 is executed, but for the content C_n+1. In other words, after the transition, the source S sends enabling data for the content C_n+1.

In parallel with the step 41, during broadcasting of the content C_n, the source S monitors the remaining time τ to broadcast the content C_n, regularly comparing it to a predefined threshold s (step 44). As soon as the remaining time τ is below the threshold s, the source S sends the enabling data DE for the next content C_n+1 via the signaling channel CS (step 45). If the remaining time to broadcast the content C_n allows, the source S sends the enabling data DE for the content C_n+1 several times before the transition between the content C_n and the next content C_n+1 (step 46).

Referring to FIG. 5, in a step 30 the receiver terminal T recovers from the source S an SDP file containing all the information necessary for receiving the signaling channel CS from the source S, by downloading it from the portal P via the Internet. To this end, as may be seen in FIG. 6, the terminal T connects to the portal P in a step 30a and downloads from the portal P a web page containing a TV guide for a plurality of channels and hyperlinks to those channels, including the channel A, in a step 30b. Under the control of a user, the receiver terminal T activates the link to the channel A in a step 30c, sending the portal P a request to acquire the SDP file from the source S. On receiving the request, the portal P sends the required SDP file to the terminal T via the Internet in a step 30d. The terminal T stores the SDP file from the source S in the memory 230 in a step 30e, in order to use it to receive from the source S either immediately after downloading or later. The SDP file from the source S contains all the information the terminal T requires to begin to receive the signaling channel CS from the source S.

To begin to receive the broadcast channels CD_x from the source S, the terminal T acquires the signaling channel CS beforehand, in a step 31 (FIG. 5). As may be seen in FIG. 7, using the Internet Group Management Protocol (IGMP), the terminal T sends a request to acquire the signaling channel CS via the Internet in a step 31a using information supplied by the recovered SDP file stored in the memory 230. In a step 31b, the first Internet router that receives this request when it is already receiving enabling data units sent by the source S duplicates the data units, which are then routed to the terminal T. Thus the terminal T receives the signaling channel CS from the source S.

In a step 32, the terminal T receives the enabling data DE relating to the content C_n being broadcast, supplied by the signaling channel CS. Each sending of enabling data contains all the information needed to receive the broadcast channels CD_x in order to recover the content C_n, the configuration characteristics enabling the received content C_n to be decoded correctly, and the marking indicator of the content C_n. The terminal T stores the enabling data DE of the content C_n with the corresponding marking indicator in its memory 234. Using the enabling data DE for the content C_n, the terminal T receives the broadcast channels CD_x from the source S in a step 33. Referring to FIG. 8, using the IGMP, the terminal T therefore sends a request to acquire the broadcast channels CD_x over the Internet in a step 33a. In a step 33b, the first Internet router that receives this request when it is already receiving the IP packets of content broadcast by the source S duplicates the IP packets and routes them to the terminal T. In a step 34, the terminal T receives the data packets of the various screens conveying the content C_n via the broadcast channels CD_x.

In a step 35, the terminal T decodes the content C_n received. For this purpose, the terminal T detects the marking indicator inserted in each IP data packet received (step 35a) in order to identify the content C_n to which it belongs, extracts from the memory 234 the enabling data DE associated with that marking indicator (step 35b), and then decodes the data packet using this enabling data DE (step 35c).

In a step 36, during broadcasting of the content C_n, the terminal C receives via the signaling channel CS the enabling data of the next content C_n+2 sent by the source S in the step 41 (FIG. 12). The step 34 is executed again after the transition 46, but this time for the next content C_n+1. Thus the terminal T receives the content C_n+1 via the broadcasting channel CD and, in parallel with this, the corresponding enabling data via the signaling channel CS.

The source S could calculate the time threshold s used in the step 44 to determine approximately the time from which it is necessary to broadcast the enabling data block of the next content C_n+1 using the following formula: s=n·T

in which:

• • T represents the time period between successive sendings of enabling data relating to the same content, and
  • n represents a natural integer whose value is such that, given the rate of non-reception of broadcast data, at least 99% of the receiver terminals receive the enabling data for the content C_n+1 at least once before the end of broadcasting the content C_n.

The value of n is generally set at 3.

The source could comprise two servers respectively broadcasting the enabling data via the signaling channel CS and the contents via the broadcast channels CD_x.

Instead of recovering the SDP file from the source S by downloading it from the portal P, the receiver terminal could recover it by any other means, for example by electronic mail or from a permanent medium such as a CD-ROM.

In the foregoing description, during the broadcasting of a content C_n, the source S monitors the remaining time τ to broadcast the content C_n and broadcasts enabling data for the next content as soon as the remaining time τ is below a threshold s. In a simplified embodiment of the invention, shown in FIG. 4a, the source S sends the enabling data of the content C_n regularly, together with that of the next content C_n+1, throughout the broadcasting of the content C_n, and there is therefore no need to monitor the remaining time to broadcast the content C_n.

Any other type of marking could be used in place of sequential indicators, provided that the respective markings of the contents of each pair of successive contents separated by a single transition are different.

Of course, the invention could be applied to any other type of computer network and in particular to any IP network.

Claims

1. A method of broadcasting a succession of contents (Cn,Cn+1) through a computer network from a broadcasting source (S) to a plurality of receiver terminals (T) able to receive from the source (S), the method comprising the steps of: for each content (Cn,Cn+1), sending (40) data units conveying said content (Cn,Cn+1) from the source (S) through the computer network, supplying the receiver terminals (T) with an indication enabling them to identify each transition between two successive contents (Cn,Cn+1), marking (40b) the data units to be broadcast by modifying the marking of the data units of successive contents separated by a single transition, and supplying to the receiver terminals (T) marking information enabling them to distinguish between data units belonging to different contents (Cn, Cn+1) with the aid of their marking.

2. A method according to claim 1, wherein the data units of a content are broadcast (40) on a broadcasting channel (CD) and the marking information relating to said content is broadcast (41) on a signaling channel (CS) separate from the broadcasting channel (CD).

3. A method according to claim 1, wherein the marking information relating a given content Cn is inserted (41a) into enabling data (DE) relating to said content (Cn).

4. A method according to claim 1, wherein the marking information relating to a content (Cn+1) is sent (41) during the broadcasting of a preceding content (Cn).

5. A method according to claim 4, wherein the remaining broadcasting time (τ) before said transition is evaluated (44) and the marking information relating to the content following said transmission is transmitted when the remaining broadcasting time (τ) is below a predefined time threshold(s).

6. A method according to claim 5, wherein the time threshold(s) is calculated using the following formula:

7. A method according to claim 4, wherein the marking information relating to the content (Cn+1) after said transition is sent regularly throughout the broadcasting of the content (Cn) preceding said transition.

8. A method according to claim 1, wherein the marking information relating to a content (Cn) is sent (41) during the broadcasting of said content (Cn).

9. A method according to claim 1, wherein a data unit is marked by inserting (40b) a marking indicator therein.

10. A method according to claim 9, wherein the marking indicator is inserted into a header of a protocol layer.

11. A method according to claim 10, wherein the marking indicator is inserted into the header of one of the layers of the group comprising the synchronization layer (SL) and the Flexmux layer.

12. A method according to claim 9, wherein sequential marking indicators are assigned to the successive contents (Cn, Cn+1, etc.).

13. A signal specifically designed for implementing the method of claim 1 to convey a succession of contents segmented into data units, which signal is characterized in that the data units belonging to different contents have respective different markings.

14. A signal according to claim 13, wherein each of the data units contains a marking indicator.

15. A signal according to claim 14, wherein the marking indicator is inserted into a header of a protocol layer of the data unit.

16. A broadcasting source adapted to broadcast a signal according to claim 13 through a computer network.

17. A source according to claim 16, comprising first sending means (14) for sending data units conveying a content (Cn) and means (120, 121) for marking the data units to be broadcast by modifying the marking of the successive contents (Cn, Cn+1, etc.) separated by a single transition.

18. A source according to claim 16, comprising second sending means for sending enabling data relating to each content (Cn) and marking information relating to said content (Cn).

19. A receiver terminal adapted to receive a signal according to claim 13 through a computer network.

20. A terminal according to claim 19, comprising first receiving means (231) for receiving data units conveying a content (Cn) and containing a marking indicator, second receiving means (232) for receiving enabling data (DE) of said content (Cn) containing an associated marking indicator, detection means (236) for detecting the marking indicator contained in each received content data unit, and decoding means (235) for decoding the received data units using enabling data associated with the detected marking indicator.