WO2009095082A1

WO2009095082A1 - Method and apparatus for distributing media over a communications network

Info

Publication number: WO2009095082A1
Application number: PCT/EP2008/051193
Authority: WO
Inventors: Mikael Lind; Andreas Ljunggren; Robert Skog
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2008-01-31
Filing date: 2008-01-31
Publication date: 2009-08-06
Anticipated expiration: 2010-07-31

Abstract

A method and apparatus for distributing media over a P2P IPTV network is described. Media frames are marked with a watermark at a node in the network such as end user equipment or a proxy node (e.g. DSLAM) before being sent to another node in the network. The watermark denotes that the frames have passed through the node, enabling tracking of data through the network. This assists in identifying distributors of pirated media. The watermark may also be made visible and used as a badge of origin.

Description

Method and Apparatus for Distributing Media over a Communications Network

TECHNICAL FIELD

The invention relates to the field of distributing media over a communications network, and in particular to distribution of IPTV using a Peer to Peer communications network.

BACKGROUND

TV services broadcast over an IP network are referred to as IPTV. IPTV is typically broadcast using a broadband access network, in which channels are transmitted over a broadband network from a super head-end down to an end-user's set top box (STB).

Linear content delivery, in which all channels in a subscription are simultaneously delivered to a user's set top box (STB), is not suitable for IPTV, as IPTV has limited bandwidth available over a broadband connection. A typical ADSL broadband connection provides a capacity of between 3 and 8 Mbps, and ADSL2 promises to deliver up to 25 Mbps downstream, whereas VDSL can provide a capacity of greater than 30 Mbps. Standard quality MPEG 2 IPTV content requires 2 Mbps per channel, and HDTV will require around 8-10 Mbps per channel. The MPEG 4 standard will approximately halve the bandwidth required to deliver IPTV content with the same quality. Nevertheless, the available bandwidth is a scarce resource, and IPTV solutions must limit the number of channels that can be delivered simultaneously.

Figure 1 illustrates a known way of distributing media in which an IPTV media stream originates in a service provider network 1 , is passed to a core network 2, is further passed into a metro network 3, and finally is sent via access networks 4 to each home network 5 that contains an STB that wishes to receive the media stream. Networks can quickly become saturated due to heavy traffic loads. In order to mitigate this problem, content can be multicast to reduce bandwidth demands for broadcast TV distribution. Furthermore, Video on Demand (VoD) services can be handled by VoD cache servers located close to the end-user. However, such caches require additional investment, and many routers would need to be replaced, as existing routers may not support IPTV multicasts. It is known to distribute an IPTV service using a Peer to Peer (P2P) network, as illustrated in Figure 2. Each STB is a peer in the network. An IPTV media stream can be delivered to a STB from another STB, from a media injector from which the stream originates, or from any other peer in the network.

The IPTV P2P requires a media injector in order to introduce the IPTV media stream into the network, although the media injector is not a true peer in the network in the sense that it only sends data but does not receive data from the peers. This is illustrated in Figure 3, which is a schematic representation of a simple IPTV P2P network 1. The network 1 includes an IPTV back-end 6 and two STBs STB1 and STB2. Each STB includes a P2P network interface 12, 13 to which is connected a video decoder 9, 11. In this example, STB1 receives the IPTV media stream from both STB2 and the IPTV back-end 6, which injects either streaming content or content from a database 7 using a P2P media injector 8. Note that other network nodes (in addition to nodes in STBs) may be peers in the network.

Note that the term "IPTV media stream" is used herein to refer to any kind of data having real time requirements, and includes Video on Demand, user generated TV content, interactive TV, interactive or co-operative games, or audio media. The media stream is to be delivered to the user such that the user can observe the media content at a constant rate without interruptions or delays. There is some latency in the P2P network, caused by buffers in each STB and the time it takes to establish communication between peers.

Compressed video media generally consists of a series of frames containing the information to be displayed on a user's screen. Each frame can be considered as a "picture" displayed on the screen. In most video compression formats, such as in ITU- T VCEG or ISO/IEC MPEG video standards, only the differences between successive pictures are usually encoded. For example, in a scene in which a person walks past a stationary background, only the moving portions of the picture are represented in each frame (either using motion compensation or as image data or as a combination of the two, depending on which representation requires fewer bits to adequately represent the picture). The parts of the scene that are not changing do not need to be sent repeatedly. However, it is still necessary for compressed media data to include some frames containing "complete" pictures, i.e. pictures encoded without reference to any pictures except themselves. These are included periodically in the media stream. Such frames are known as "l-frames" ("intra-frames")or "key frames".

For example, MPEG media streams contain different frames, such as l-frames, P- frames and B-frames. l-frames do not depend on data contained in the preceding or following frames, as they contain a complete picture. P-frames provide more compression than l-frames because they utilize data contained in the previous l-frame or P-frame. When generating a P-frame, the preceding frame is reconstructed and altered according to incremental extrapolation information. B-frames are similar to P- frames, except that B-frames interpolate data contained in the following frame as well as the preceding frame. As a result, B-frames usually provide more compression than P-frames. In some systems, every 15th frame or so is an l-frame. P-frames and B- frames might follow an l-frame as follows: IBBPBBPBBPBB(I). The order and number of frames in the sequence can be varied.

The media stream includes payload data and metadata. The payload data is the media data itself, and is decoded and shown by the receiver. Payload data typically comprises frames as described above. The metadata includes all other data in the media stream. This may be, for example, data describing the payload data, or information establishing signalling between two peers. In order to facilitate handling of the media stream, the media stream is sent in "fragments". Fragments are discrete portions of the media stream containing both the payload data and the metadata. It will be appreciated that a frame and a fragment do not necessarily correspond to each other directly: a single frame may be encoded into many fragments or (in some cases) a single fragment may contain more than one frame.

One problem often associated with P2P networks is the identification of pirated material. If a user were to distribute pirated content (for example, media recorded from a HDTV feed using an existing broadcast or multicast system) it would be very difficult to track down the perpetrator.

There is thus a need for a system enabling the identification of distributors of pirated material. SUMMARY

In accordance with a first aspect of the present invention there is provided a node for use in a P2P network, preferably an IPTV P2P network. The node comprises a processor arranged to mark media frames with a watermark which denotes that the frames have passed through the node. A transmitter is operatively connected to the processor and arranged to transmit the media frames to one or more other nodes in the network.

Thus by identifying the watermark, any given node through which media has passed can be identified. The data path can be tracked by use of the watermarks, and the source can be identified.

The node may be, for example, end user equipment or near end user equipment such as a proxy node, or it may be a media injector. In some circumstances, the node may be the originator of the media data. In other circumstances (e.g. if the node is a proxy node), the data may have originated elsewhere. The node may therefore include a receiver operatively connected to the processor and arranged to receive media frames, some or all of which will be marked by the processor, and a memory operatively connected to the receiver, processor and transmitter and arranged to cache the media frames. The invention may also be used in home P2P and store and forward networks. For example, the node may be an ethernet-enabled DVD recorder, personal router, or DVD-recorder or other digital recording device.

In one embodiment, the watermark may be invisible to a viewer of the media. The viewer should not even be aware of the watermark's presence. In this embodiment, the law enforcement authorities should have equipment suitable for decoding the watermark so as to identify each node through which the data has passed.

In another embodiment, the watermark may be visible to the viewer. The watermark may therefore be usable as a badge of origin. For example, a particular operator might mark media data as having originated from that operator. It will be appreciated that these two embodiments are not mutually exclusive. For example, data might be marked with an invisible watermark (for tracking) and a visible watermark (as a badge of origin). The tracking watermark may also identify the time at which the media passed through each node. In accordance with a second aspect of the present invention there is provided a method for distributing media in a P2P network. The method comprises, marking media frames at a node in the network with a watermark, the watermark denoting that the frames have passed through the node. The frames are then sent to another node in the network. The method may further comprise deciphering the watermark to identify each node through which the media frames have passed, and preferably also the time at which they passed through each node.

According to a third aspect of the present invention, there is provided a program for controlling an apparatus to perform a method according to the second aspect of the present invention.

The program may be carried on a carrier medium, which may be a storage medium or a transmission medium.

According to a fourth aspect of the present invention, there is provided an apparatus programmed by a program according to the third aspect of the present invention.

According to an fifth aspect of the present invention, there is provided a storage medium containing a program according to the third aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates schematically in a block diagram an architecture for the distribution of IPTV;

Figure 2 illustrates schematically in a block diagram an architecture for the distribution of IPTV in a peer to peer network;

Figure 3 illustrates schematically in a block diagram a media injector and two Set Top

Boxes;

Figure 4 illustrates schematically in a block diagram the signalling required to initiate an

IPTV broadcast with a first Set Top Box; Figure 5 illustrates schematically in a block diagram the signalling required to initiate an

IPTV broadcast with a further Set Top Box;

Figure 6 illustrates schematically in a block diagram keep alive messages sent by a Set

Top Box; Figure 7 is a schematic illustration of the use of a proxy node; Figure 8 is a schematic block diagram of a node; and

Figure 9 is a flow diagram illustrating the actions taken by a node in adding a watermark to media frames.

DETAILED DESCRIPTION

The following description sets forth specific details, such as particular embodiments, procedures, techniques, etc. for purposes of explanation and not limitation. In some instances, detailed descriptions of well known methods, interfaces, circuits, and devices are omitted so as not obscure the description with unnecessary detail. Moreover, individual blocks are shown in some of the drawings. It will be appreciated that the functions of those blocks may be implemented using individual hardware circuits, using software programs and data, in conjunction with a suitably programmed digital microprocessor or general purpose computer, using application specific integrated circuitry, and/or using one or more digital signal processors.

Figure 4 illustrates typical signalling required to initiate an IPTV broadcast with a first STB STB1. The video decoder 9 in STB1 receives an instruction from a user to start channel X. This is relayed to the P2P network interface 12 in STB1 , which sends a request to a STB manager 10 in the IPTV back-end to join channel X. The STB Manager 10 returns a peer list to the network interface 12 in STB1 , but no IPTV media stream. The peer list includes the P2P media injector 8. Since the media injector can be considered as a peer in the network it is hereinafter referred to as STBO. The network interface 12 in STB1 then sends a request to join channel X to STBO. STBO receives an IPTV media stream from an IPTV media stream source (for example from the database 7 shown in Figure 3), and sends a peer list and an IPTV media stream comprising fragments of frames to the network interface 12 of STB1. The network interface 12 sends the frames to the video decoder 9 in STB1 , which can then show the IPTV media stream to the user.

Figure 5 illustrates typical signalling required to initiate an IPTV broadcast with a further STB STB2. It is assumed that STB1 is already receiving an IPTV media stream from STBO. When the user of STB2 wishes to receive channel X, she sends an instruction to logic within STB2, which is relayed to the network interface 13 in STB2. The network interface 13 in STB2 sends a request join channel X to the STB manager 10. The STB manager 10 returns a peer list but no payload to STB2. The peer list includes STBO and STB1 , as these are both possible sources for the IPTV media stream. The network interface 13 in STB2 then sends a request to each of STBO and STB1 to join channel X. STBO and STB1 each send a peer list and IPTV data stream to the network interface 13 in STB2, which passes the frames of the IPTV media stream to the video decoder.

All peers in the P2P network may send each other "keep alive" messages, as illustrated in Figure 6, to ensure that each STB is included in the list of peers and can both send and receive IPTV media streams.

Note that the term "IPTV media stream" is used herein to refer to media data having real time requirements, and includes Video on Demand, user defined TV content, interactive TV, interactive or co-operative games, or audio media. The media stream is to be delivered to the user such that the user can observe the media content at a constant rate without interruptions or delays. There is some latency in the P2P network, caused by the buffer in each STB and the time it takes to establish communication between peers. The media stream may come from a media injector originally, but can also be received from other nodes within the network. A media stream contains both payload data (that is, data used for showing the media channel) and metadata (which includes data describing the media stream).

It will be appreciated that, in some instances, a proxy node near to the end-user may be used to send and receive media streams on behalf of the end user. For peers with an asymmetrical connection, the proxy node will make those peers appear to be good peer to peer citizens as far as the other peers are concerned. Furthermore, the proxy node can be used to disguise the fact that it is acting on behalf of a plurality of clients. The proxy node may be a new entity within the network, or may be provided as a function located in an existing network node.

An example of a node that could be used as a proxy node in this application is a Digital Subscriber Line Access Multiplexer (DSLAM). A DSLAM is a network device, located near the end user's location, that connects multiple Digital Subscriber Lines (DSLs) to a high-speed Internet backbone line using multiplexing techniques. A typical DSLAM may serve 2000 subscribers, which would allow a single media stream to be sent to 2000 STBs. As illustrated in Figure 7, the proxy node 71 is seen simply as another peer in the network 72, and can be used to store real-time media streams in the content distribution network.

The proxy node can also act on behalf of an end user device when the end user device is the source of the media stream (effectively, the end user device is acting as a media injector). In this case, the proxy node can disguise the fact that there are a plurality of end-user devices located "behind" the proxy node in the network, as the proxy node effectively constructs its own network subnetwork. The proxy node can also allow an end-user device to hide its identity in the network when the end-user device is acting in the role of a media injector.

Nodes such as end-user equipment (i.e. STBs) and/or near end user equipment (e.g. DSLAMs) and/or operators include a functionality that introduces small modifications to some or all of the media frames whenever they are transmitted from that node. The modification should identify the node transmitting the data, and the time at which the data is transmitted. This modification may be seen as a form of steganography - i.e. the modification should be invisible to the viewer, but is detectable by law enforcement agencies. This enables data which passes through the network to be "tagged" so that its route through the network can be identified.

It will be appreciated that there are a variety of ways in which "invisible" modifications may be made to the media content. One example might involve adding a series of dots into each key frame (I frame), the dots encoding information about the node doing the insertion. The dots would be invisible to the viewer, but could be viewed using suitable equipment if there is a suspicion that the media has been pirated. Alternatively, intermediate frames (P frames and B frames) include movement vectors, and these could be amended by a small amount which is not detectable by eye, in order to record details of the node transmitting the data. It will also be appreciated that the indicator need not be visual: it is also possible to include audio tags to identify each node which has transmitted the media.

Whatever method is chosen, it is the media data itself (the frames) which is tagged, rather than the data fragments (including metadata) into which the frames are encoded.

If every node which has access to the media data makes some modification to the frames before transmission, it is then possible to deduce the path that the data has taken through the network, and thus discover which operators and end-users were involved in creating the pirated media.

A similar functionality may also be used to modify the content in a much more visible way, allowing an operator to brand a video. For example, a watermark "Distributed via Operator X" could be introduced into all frames sent from a particular operator so that users can see where the content originated. Similarly, such a watermark might denote geographical origin, so that operators distributing media in different areas use a separate watermark for each area.

Figure 8 illustrates an example of a node 81 that could be used to tag or watermark data. The node 81 could be a STB such as STB1 shown in Figures 3-5, or a proxy node such as the proxy node 71 (DSLAM) shown in Figure 7. Alternatively, the node could be an operator node such as STBO. The node 81 has a receiver 82 for receiving media frames from one or a plurality of sources, a processor 83, a memory 84 for caching media data, and a transmitter 85 for sending media to other peers in the network. The processor is capable of marking individual frames of the data so as to ensure their traceability. It will be appreciated that the frames will be transmitted and received in the form of data fragments, although where the node is a media injector, the media may be received in the form of frames from a media encoder.

The receiver may be implemented as a software module in a television set, which will then be able to receive IPTV from the network and display it to the user. Alternatively, the set-top box is implemented as a software module, for example in a personal computer or other terminal having data processing capabilities. The stream can then be forwarded from the set-top box to any display unit, including a television set, or the computer's own display for display to the user.

Figure 9 is a flow diagram illustrating a sequence of actions taken by a node in marking frames.

S1 : Data fragments media data are received from another node in the network.

S2: Media frames are extracted from the data fragments. S3: Selected frames are marked with a watermark, which may be visible (as branding) or may be invisible (for data tracking).

S4: The frames, including the marked frames, are encoded as data fragments.

S5: The fragments are forwarded to other nodes in the network.

It will be appreciated that step S1 will not always be necessary: for example, if the media is generated at that node, then data fragments will not be received from elsewhere.

Thus the invention provides accountability for pirated content even if Digital Rights Management (DRM) is removed. It ensures traceability in the network and enables the identification of rogue elements. Furthermore, it provides for visibility and personalised branding by operators or even end-users.

It will be appreciated that variations from the above described embodiments may still fall within the scope of the claims. For example, the set top boxes have all been described as including "video decoders" but it will be appreciated that decoding for any form of media may be envisaged.

It will also be appreciated that the above described embodiments have been described with reference to P2P IPTV networks, but the invention may also be used in other nonlinear environments, for example top down networks and store and forward networks. The invention may also be used in other networks such as personal P2P and store and forward networks, for example DVD player → Router → DVD recorder, ensuring that a perpetrator can be tracked via his router.

Although various embodiments have been shown and described in detail, the claims are not limited to any particular embodiment or example. None of the above description should be read as implying that any particular element, step, or function is essential such that it must be included in the claims' scope. The scope of protection is defined by the claims.

Claims

CLAIMS:

1. A node for use in a Peer-to-Peer network, comprising: a processor arranged to mark media frames with a watermark, the watermark denoting that the frames have passed through the node; and a transmitter operatively connected to the processor and arranged to transmit the media frames to one or more other nodes in the network.

2. The node of claim 1 , further comprising a receiver operatively connected to the processor and arranged to receive media frames, some or all of which will be marked by the processor, and a memory operatively connected to the receiver, processor and transmitter and arranged to cache the media frames.

3. The node of claim 1 or 2, which node is end user equipment.

4. The node of claim 1 or 2, which node is a proxy node.

5. The node of claim 1 or 2, which node is a media injector.

6. The node of claim 1 or 2, which node is a DVD player, personal router, DVD- recorder, or personal digital media recorder.

7. The node of any preceding claim, wherein the watermark is invisible to a viewer of the media.

8. The node of any of claims 1 to 6, wherein the watermark is visible to the viewer and identifies to the viewer that it has passed through the node.

9. The node of any preceding claim, wherein the watermark identifies when the media frames passed through the node.

10. The node of any preceding claim, wherein the network is an IP Television Peer- to-Peer network.

1 1. The node of any preceding claim, wherein the network is a top down network or a store and forward network.

12. The node of any preceding claim, wherein the network is a home Peer-to-Peer or store and forward network.

13. A method for distributing media in a Peer-to-Peer network, comprising: at a node in the network, marking media frames with a watermark, the watermark denoting that the frames have passed through the node; and sending the frames to another node in the network.

14. The method of claim 13, wherein the node is end user equipment, a proxy node, or a media injector.

15. The method of claim 13 or 14, wherein the watermark is invisible to a viewer of the media.

16. The method of claim 13, 14 or 15, wherein the watermark identifies when the media frames passed through the node.

17. The method of any of claims 13 to 16, further comprising tracking a route of data through the network by examining the watermarks added by each node.

18. The method of claim 13 or 14, wherein the watermark is visible to the viewer and identifies to the viewer that it has passed through the node.

19. The method of any of claims 13 to 18, wherein the network is an IP Television Peer-to-Peer network, home Peer-to-Peer network, top down network or store and forward network.

20. A program for controlling an apparatus to perform a method as claimed in any one of claims 13 to 19.

21. A program as claimed in claim 20, carried on a carrier medium.

22. A program as claimed in claim 21 , wherein the carrier medium is a storage medium.

23. A program as claimed in claim 21 , wherein the carrier medium is a transmission medium.

24. An apparatus programmed by a program as claimed in any one of claims 20 to 23.

25. A storage medium containing a program as claimed in any one of claims 20 to 22.