GB2535686A

GB2535686A - A hybrid satellite internet protocol television and peer to peer transmission system

Info

Publication number: GB2535686A
Application number: GB1421732.7A
Authority: GB
Inventors: Jim Kelley Glasspool Andrew; Robert Whitworth Ian
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-12-07
Filing date: 2014-12-07
Publication date: 2016-08-31
Also published as: GB201421732D0

Abstract

A hybrid satellite internet protocol television (IPTV) and peer to peer (P2P) transmission system is disclosed which facilitates the distribution of satellite broadcasts, from a satellite receiver over an ad-hoc exclusively dedicated peer-to-peer network 10, 11 of set top boxes (STBs, television receivers), facilitating reception by users without conventional satellite receivers and with unreliable internet connectivity (poor quality of service, QoS). The system imposes watermarking using common and watermarked (receiver-specific) channels - to enable traitor tracing and prevention of unauthorised redistribution. The watermarking is adapted to minimise satellite transmission overhead. The peer to peer enabled receiver may be a computer, tablet or smartphone. A combination of satellite receiver and a seed peer server adapted to receive pieces (segments) of an IPTV file or stream and distribute them via the seed peer to peer network is also claimed.

Description

Intellectual Property Office Application No. G131421732.7 RTM Date:10 May 2016 The following terms are registered trade marks and should be read as such wherever they occur in this document: Wi-Fi (Page 12) Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo

A HYBRID SATELLITE INTERNET PROTOCOL TELEVISION AND PEER TO PEER TRANSMISSION SYSTEM TECHNICAL FIELD

mou The present invention concerns internet protocol television (IPTV) or over the top (OTT) transmission via a wide area network (WAN), especially the internet. It is more particularly, but not exclusively, concerned with delivering real time, live broadcasts sourced from satellite transmissions where the WAN lacks dependable acceptable levels of quality of service (QOS). The system is further concerned with monitoring and controlling unauthorised redistribution of content.

PRIOR ART

[002] It is known to broadcast content over an internet protocol network; however receiving content in real time presents a particular problem where the quality of service of the user's Internet connection is poor. In particular the most popular real time events will tend to raise the traffic levels in the WAN (Internet) exacerbating the QoS problem. There remain many regions where high speed reliable broadband is not available so that prolonged delays and interruptions to service occur. Particularly in the case of live event broadcasts this is unacceptable. These regions often correspond to regions of poor or limited terrestrial television coverage.

MON Satellite TV transmission models have one server directly serving a large number of clients, usually in the form of set top boxes which decode a satellite transmission received from a satellite. The set top box is primarily a device for decrypting what is usually an encrypted transmission and may provide digital to analogue conversion functions where the set is still analogue. For the purpose of this specification the term "set top box" may include this functionality integrated with a conventional TV set.

[4] Internet protocol television broadcasts (IPTV) models have one head end server delivering internet packets from an IPTV file or content stream segment in sequence to one set top box. The packets are usually encrypted and the function of the set top box is to receive and decrypt each packet in order sequence as it is received from the server.

[5] To avoid the overhead of TCP/IP transmission protocols and the consequent network overhead IPTV is commonly transmitted using UDP. On networks where the QoS is already poor the known vulnerability of UDP packets to loss and corruption is exacerbated.

[OM In regions of poor WAN QoS direct broadcast satellite (DBS) is a popular source of for real time, especially live content reception. However there are regions where DBS cannot be received reliably. In many regions where the WAN suffers poor QoS the cost of satellite equipment and subscription is unacceptably high. DBS cannot readily interface with increasingly popular mobile receivers such as tablets and smart phones and cannot provide the interactive services and feedback of a WAN.

[007; The present invention aims to address some of the technical issues recited above.

STATEMENTS OF INVENTION

[0081 The present invention provides a hybrid satellite IPTV system wherein a head end server transmits content to a plurality of satellite receivers and each satellite receiver delivers content to a plurality of set top boxes characterised in that the set top boxes are adapted to run executable code to serve as peers in a peer-to-peer network.

[009; According to a second aspect of the present invention there is provided a set top box capable of receiving and decoding an IPTV file or stream content segment communicated via media and characterised in that the set top box has a memory storing code executable in a processor to cause the set top box to act as a peer and establish a peer-to-peer network for reception of pieces of the IPTV file or content stream.

According to a third aspect of the present invention there is provided a package of code deliverable via media to install code capable of execution in a set top box to enable the set top box to act as a peer in a hybrid satellite IPTV peer to peer network.

gin] According to a fourth aspect of the present invention there is provided a method of operating a hybrid satellite IPTV peer to peer network comprising: a head end server communicating an IPTV file or stream content divided into coded pieces of data, via satellite, to a plurality of satellite receivers; each satellite receiver communicating the IPTV file or stream content to an associated peer-to-peer network of peer to peer enabled set top boxes, said set top boxes downloading the pieces to complete said file or content from any set top box peer to peer source available, said file pieces being downloaded in any arbitrary order as they become available and being ordered for playback by the set top box.

[12] A metadata file is distributed to all peers including; the hash for every piece, mapping for each piece to the file or content stream segment, and a tracker reference. Preferably the P2P client established by the executable code will assume that all the pieces of; the file or particular segment, of the content stream are required. The set top box peer will therefore be able to identify and request missing pieces from nearby set top box peers. When the number of operating peers is large, the number of routes between peers becomes large and localised poor QoS problems can be overcome with higher confidence.

[13] According to a fifth aspect of the present invention there is provided a satellite receiver adapted to receive pieces of an IPTV file or content stream segment adapted for distribution via a peer-to-peer network.

[14] The peer to peer network is preferably an ad-hoc peer to peer network and more preferably the ad-hoc peer-to-peer network is dedicated, preferably exclusively, to a single satellite receiver and cannot function as a general purpose peer to peer network and interface with other peer to peer networks. This can be achieved by the implementation of an exclusive hand shaking protocol.

[15] Preferably the executable code will establish a set top box peer which requests missing pieces of a file or content segment using a rarest piece first algorithm. A tracker may facilitate this function.

[0161 Advantageously each piece or segment may be divided into a plurality of blocks.

The blocks will preferably be of equal size. The blocks will preferably be encoded using an erasure code, preferably a fountain code (sometimes known as a rateless erasure code) and most preferably a raptor code. Raptor codes will facilitate the recovery of a piece from a number of blocks in the event that one or more blocks are lost or damaged on receipt. Preferably the head end server will divide the pieces into blocks and apply the raptor coding to blocks of a size appropriate to the peer-to-peer network.

[0171 Both the fountain coding and P2P (torrent) protocol can have matched pieces and blocks. This can facilitate delivery of pieces and blocks from any peer.

[0181 A torrent tracker may provide feedback to the head server to facilitate bandwidth control.

[019] The system may implement traitor tracing to identify peers in the peer-to-peer network from which pieces or blocks of the file are leaked (distributed) to unauthorised devices. This may be achieved by watermarking. At intervals the content within a specified piece may be watermarked and transmitted simultaneously with the specified piece unmarked. Each satellite receiver will have a unique identification and address. A conditional access system (CAS) will distribute each of the marked and unmarked pieces to different satellite receivers, or groups of satellite receivers using the unique receiver address. So for example the piece containing marked blocks may be distributed to a first group of receivers while the piece containing unmarked blocks are distributed to a second group of receivers. A subsequently transmitted piece of the file may distribute unmarked pieces to the first group, and marked pieces to the second group. Watermarking is preserved over the P2P distribution. The fountain coding will cooperate with the watermarking so that an unmarked block cannot contribute to decoding a marked block, and similarly a marked block cannot contribute to the recovery of an unmarked block. The CAS will ensure that the marking and distribution of the pieces is such that over a period of time the content decoded by each satellite receiver will contain a unique sequence of marked and unmarked pieces. This will allow unauthorised distribution of the file to be traced to a specific satellite receiver. Only a limited proportion of the content need be watermarked, so that the overhead of watermarking is small. The unique sequence may be built up over a period, such as the duration of a sports match, or a movie (both of which are premium content and worth protecting.

[020; The tracker may collect data on the path of the pieces to provide traceability independent of the watermarking.

[0271 Tracking and watermarking may be configured to enable the location of a leaking satellite receiver or its associated peer-to-peer network sufficiently quickly to implement steps to block the leak during file transmission. This could involve shutting down a peer or a satellite receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

[0221 An embodiment of a hybrid satellite IPTV and peer to peer transmission system according to the present invention will now be described, by way of example only, with reference to the accompanying illustrative figures, in which: Figure 1 is a diagrammatic illustration of the system; Figure 2 is a flow chart of the process implemented by the system; Figure 3 is a flow chart illustrating aspects of the process implemented in a set top box by executable code; Figure 3A is an enlarged view of a satellite receiver and seed peer combination.

DETAILED DESCRIPTION OF THE DRAWINGS

[023] Figure 1 diagrammatically illustrates the system and shows an IPTV file source 1 represented in this case by a camera to capture a live event. However the source may be a recording on media. The source file is digitised at a head server 2 and subject to processing according to the steps of the process illustrated in figure 2.

10247 The head end server 2 may digitise the file if it is not already in digital format before dividing the file into pieces of equal size at step 103. At step 104 the head end server divides each piece into blocks, which are preferably of equal size. At step 105 each block is encoded using the raptor class of fountain codes. Raptor codes allow an arbitrary tolerance to block erasures. Raptor codes obey a linear law in block length for decoding time making them well suited to simple receivers with high data rates.

[025] A piece comprising raptor coded blocks facilitates the recovery of lost or damaged blocks from a fraction of received blocks without requiring retransmission of lost or damaged blocks.

[0261 At steps 106 and 107 a procedure is implemented to select or deselect pieces for a watermarking subroutine or unmarked broadcast. The piece counter is implemented at step 106 and counts the number of pieces sequentially processed from the file and compares this to an integer watermark value Np. When n does not equal Np the process goes to step 108 where a common encryption key is applied to the piece.

[27] The piece is then wrapped. The wrapper may be a Torrent wrapper including a cryptographic hash. The piece is then transmitted to a satellite 6 via a common uplink ground station 3 at steps 114 and 115. The piece is retransmitted from the satellite and received at each of the first ground receiver station 4 and second ground receiver stations 5 at steps 117 and 116.

[28] Each ground station 116, 117 communicates the piece to a seed peer in a corresponding one of a first peer ad-hoc peer-to-peer network 10 and a second peer ad-hoc peer-to-peer network 11. Pieces continue to be delivered to the seed peer until the file is complete.

[29] Peers 8 other than seed peers are controlled by a peer to peer client to request pieces of the file from any other nearby peer in the ad-hoc peer-to-peer network. Pieces are collected in any order as they become available and are reordered in accordance with the hash associated with each piece wrapper. Fountain codes allow damaged or missing blocks to be recovered without retransmitting pieces and thereby minimise traffic demands.

[30] When the head end server detects that the number of peers n equals the integer watermark value Np a watermarking process is applied to the Npth piece. In this case the procedure goes to step 109 where the piece is copied into first and second channels defined by different encryption keys.

[31] Each ground station 4, 5 is adapted by means of a conditional access system to be able to communicate only a single specific piece encrypted onto one channel. Accordingly the piece from only one channel will be communicated to the ad-hoc peer-to-peer network. This might be achieved by arranging the receiving stations 4 and 5 so that it preferentially communicates any specific piece wrapped with watermark encryption over common encryption.

[32] The head server operates to divide the file into pieces corresponding to an integer number of frames. For example one piece may correspond to 20 seconds or 20 x 24=480 frames. A group of pictures (GOP) is the picture frames contained in a single piece. Or to put it another way, the size of a piece is selected by the head server to contain an integer number of picture frames.

[33] At step 110 a first invisible watermark is applied to the group of pictures (GOP) copied to the first channel. At step 111 a different invisible watermark is applied to the second copy of the piece. In practice the different watermark can be no watermark. In either channel the pieces for watermarking are chosen so that each channel has a unique sequence of watermarked GOP's or pieces.

[34] Each copy of the piece is encrypted at steps 112 and 113 and packaged in a wrapper before forwarding for transmission from the uplink ground station 3 to the satellite 6. In this embodiment the first ground station 4 receives the first channel while the second ground station 5 receives the second channel.

[035; The first ground station 4 then retransmits the piece to one or more seed servers 7.

Each seed servers 7 will have a complete copy of the file which can then be delivered piece by piece to peers 8 which comprise the ad-hoc peer-to-peer network.

[036] Each peer 8 is established by a P2P client application. The peers 8 in this case are preferably set top boxes which may be delivered to users with the client pre-installed. However the P2P client may be installed via a network download onto pre-existing set top boxes as illustrated in figure 3. The client may also be installed from other media such as a flash drive or optical media such as CD or DVD.

1037.1 Once a peer has been established by running executable code on a processor of the set top box, a tracker server will be established with a database of the location of pieces of the file at least on nearby peers. The hash of pieces already received will identify any missing pieces and allow the peer to request each missing piece from nearby peers in accordance with data provided by the tracker. The tracker will update as the missing pieces are delivered.

[038] A specific piece will correspond to a specific integer number of frames, for example in a specific time period of the file, for example the first 20 seconds. So for a specific piece there may be two copies A and A' distinguished in that they are delivered on different channels with different watermarking and different fountain coding but otherwise contain the same data. Only pieces from a common channel with common watermarking can contribute to the recovery of blocks with common watermarking. So for example where a piece has a first watermarked copy A and a second copy A' "watermarked" by no watermark, the blocks containing watermarked content cannot contribute to the recovery of the piece "watermarked" by no watermark. Invisible watermarking integrity is preserved over the system, in particular over the P2P distribution.

[39] Over a period of time which can be set to correspond to the duration of the file, (for example 1-3 hours in the case of a film) content decoded by each ground station receiver will contain watermarked pieces in a time pattern unique to the specific ground station receiver 4. This enables any subsequent unauthorised distribution of the content to be traced to the specific receiver.

[40] In a specific example of watermarking a file contains pieces each with 20s of content (eg 20 x 24 frames). Watermarking is applied periodically to a piece every 300s (5 minute). For a file of duration 2hrs there may be 24 watermarked pieces. This allows unique identification of a satellite receiver by content watermarking with a time sequence of 1 in 224=4 billion.

[41] By applying the watermarking periodically the overhead on the satellite link is minimised.

[42] The tracker can provide information on where the pieces of the file have been sent and thereby provide traceability independently of the watermarking.

[43] Because watermarking survives retransmission over media, it is possible to detect which ground station and therefore which ad-hoc peer-to-peer network is leaking. Leaks may also occur from an individual peer. By delivering different watermarked sequences of pieces to different seed peers and tracking their delivery to different peers it may be possible to isolate a specific leaking peer and shut it down during transmission of the program.

[044] Figure 3 illustrates a process of downloading, installing and running a P2P client to establish the set top box functionality for a hybrid network on either an existing set top box or a device with internet connectivity such as a WiFi and/or 3G or 4G enabled PC, tablet, or smart phone. Such devices may be capable of acting as a set top box and presenting the received content as well as serving as peers in the P2P ad-hoc peer-to-peer network. For the purpose of this description the term set top box should be understood to include all such devices.

[0451 At step 201 the device establishes an internet connection to establish an account with the satellite content provider. Establishing an account will consist of confirming that the user has authority to access the content.

[048] The content provider's server, which in this example will be a seed server, delivers a package of code to the set top box which is recorded in the set top box non-volatile memory. The package is then unwrapped and installed in accordance with known processes. When the executable code runs on the set top box processor it enables the set top box to acquire the tracker at step 205 and request pieces of an I PTV content file at step 206 from other peers in the ad-hoc peer-to-peer network. The client will enable the set top box to request pieces and on receipt to decrypt and decode pieces at step 207. Missing or corrupted pieces can be identified from the hash at step 208 and missing or damaged blocks within the hash can be repaired using the fountain codes. Received pieces can be recorded to memory at step 209 and reported to the tracker for feedback to the head server at step 210. At step 211 the set top box can respond to other peer requests for pieces by communicating recorded pieces.

Claims

CLAIMS1. A hybrid satellite IPTV system wherein a head end server transmits content to a plurality of ground satellite receivers, and each satellite receiver delivers a file or streaming content segment to a plurality of set top boxes characterised in that the set top boxes are adapted to run executable code to serve as peers in a peer-topeer network.
2. A system according to claim 1 wherein each ground satellite receiver is capable of receiving a signal encrypted to provide a common channel and a watermarked channel, wherein the common channel is common to a watermarked channel is unique to each ground satellite receiver.
3. A system according to claim 2 wherein a head end server is adapted to: acquire an IPTV file or stream content segment; divide the file into pieces for distribution across an peer-to-peer network; periodically select and copy a piece to a first watermarked channel; apply a first invisible watermark to each frame of a group of pictures contained in the piece; and copy the selected piece to a second watermarked channel; apply a second invisible watermark to the piece in the second watermark channel; transmit the pieces for rebroadcast from a satellite towards at least two ground receiver stations so that only one of the first and second watermarked pieces can be received by one of the ground receiver stations and only the other by the other of the ground receiver stations.
4. A system according to claim 3 wherein one of the first or second invisible watermarks may be no watermark.
5. A system according to claim 3 wherein the head end server is adapted to determine the size of each piece so that the content of the piece corresponds to an integer number of frames.
6. A system according to any one of the preceding claims wherein the head end server divides each piece into blocks, and encodes each block using fountain code.
7. A system according to claim 6 wherein the fountain code is a raptor code.
8. A system according to claim 6 or claim 7 wherein the blocks are of equal size.
9. A system according to any one of the preceding claims wherein the peer to peer network is a dedicated exclusive peer to peer network.
10. A system as herein described with reference to the accompanying figures.
11. A set top box capable of receiving and decoding an IPTV file or stream content segment communicated via media and characterised in that the set top box has a memory storing code executable in a processor to cause the set top box to act as a peer and establish a peer-to-peer network for reception of pieces of the IPTV file or stream content segment.
12. A set top box according to claim 11 wherein the set top box is one of: a dedicated device which provides an interface between a terrestrial television and an internet gateway and is only capable of receiving an I PTV file or stream content segment via a single peer-to-peer network; a general purpose computer, tablet or smartphone.
13. A package of code deliverable via media to install code capable of execution in a set top box to enable the set top box to act as a peer in a hybrid satellite IPTV peer to peer network.
14. A package according to claim 13 wherein the media is a file server storing a copy of the package in a form communicable via the internet.
15. A package according to claim 13 wherein the media is a solid state memory including any of: an optical storage disc or flash memory.
16. A method of operating a hybrid satellite IPTV peer to peer network comprising: a head end server; acquiring an IPTV file or stream content segment or dividing the file or stream content segment into pieces transmitting the pieces via satellite to at least one satellite receiver; said satellite receiver communicating the pieces of the IPTV file or stream content segment to a dedicated peer-to-peer network of peer to peer enabled set top boxes, said set top boxes downloading the pieces to complete said file or stream content segment from any set top box peer of the peer-to-peer network.
17. A method according to claim 16 wherein said file or stream content segment pieces are downloaded in any order as they become available and being ordered for playback by the set top box.
18. A method according to claim 16 or 17 wherein the head server applies encryption to each piece such that only a dedicated satellite receiver can receive it.
19. A method according to any of claims 16 to 18 wherein the IPTV file or stream content segment is transmitted to each of at least two satellite receivers.
20. A method according to claim 19 wherein each satellite receiver is capable of receiving file or stream content segment pieces encrypted in wrappers using either; a common code, or a watermark code wherein the common code is common to every satellite receiver on the network and each watermark code maps uniquely to each satellite receiver; the head server transmitting some pieces using a common code encryption receivable by all the satellite receivers; the head server selecting a certain piece at a certain time, making a first and second copy of the certain piece, applying a first invisible watermark to a first watermark copy of the certain piece encrypting the watermarked copy of the certain piece with the watermark code, applying a second invisible watermark to the second copy of the piece, applying the common encryption code to the second copy of the certain piece, transmitting each of the common copy and the watermark copy of the certain piece via satellite so that the watermark copy only is communicated to the peer-to-peer network associated with one specific satellite receiver, and the common copy is communicated to each peer-to-peer network associated with every other satellite receiver; selecting a subsequent certain piece and applying steps (b) to (e) using a watermark encryption code for a different satellite receiver, whereby each satellite receiver distributes an IPTV file or stream content segment to the corresponding peer-to-peer network with a sequence of watermarked groups of pictures unique to the satellite receiver.
21. A method according to claim 20 wherein the head end server determines the size of each piece to correspond to an integer number of frames.
22. A method according to claim 20 wherein the one of the first and second watermarks can be no watermark.
23. The combination of a satellite receiver and a seed peer server adapted to receive pieces of an IPTV file or stream content segment and distribute them via the seed peer to a peer-to-peer network.
24. The combination according to claim 23 adapted to preferentially distribute a specific piece received and encrypted with a specific watermark code over the same piece encrypted with a common code, where the specific watermark code is a watermark code unique to each specific satellite receiver.