WO2009103346A1

WO2009103346A1 - Method and apparatus for obtaining media over a communications network

Info

Publication number: WO2009103346A1
Application number: PCT/EP2008/052187
Authority: WO
Inventors: Andreas Ljunggren; Robert Skog
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2008-02-22
Filing date: 2008-02-22
Publication date: 2009-08-27
Also published as: GB2469947A; GB201011824D0; GB2469947B

Abstract

A method and apparatus for receiving an IPTV channel over a communications network. Media fragments for a first IPTV channel are received at a node. A determination is made that network conditions are insufficient to provide the first IPTV channel at a desired quality. As a result of the determination, the media fragments for a second IPTV channel are requested, such that the second IPTV channel provides the same media content as the first IPTV channel but at a quality that requires a lower bandwidth than the first IPTV channel. An exampleof an IPTV channel that requires a lower quality is where the first channel provides High Definition media fragments and the second channel provides Standard Definition media fragments.

Description

Method and Apparatus for Obtaining Media over a Communications Network

TECHNICAL FIELD

The invention relates to the field of obtaining media over a communications network, and in particular to obtaining IPTV media data.

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.

An STB receives a media stream in the form of fragments. A buffer containing fragments is illustrated in Figure 3. A fragment may contain both metadata about the media stream, and payload data from the media stream itself. The P2P network interface (in, for example, a STB) requests fragments from other P2P peers. In Figure 3 the P2P logic is writing fragment number 21 into the buffer and fragment number 17 is sent to the video decoder.

Where fragments (including media frames) are distributed over a P2P network, they are typically distributed over best effort bearers. In other words, the bearers have no Quality of Service (QoS) requirements (i.e. there is no QoS in the system).

A new generation of IPTV channels, such as High Definition TV (HDTV) now require more bandwidth than Standard Definition TV (SDTV) to distribute, because an HDTV channel requires more information to be conveyed to the destination. With the increasing availability and reducing cost of providing bandwidth to users, this is not normally a problem. However, in circumstances where network conditions deteriorate and the available bandwidth is reduced for some reason, for example owing to a volume of traffic over a particular link, then some HDTV media fragments may be lost. This can have a negative impact on the user's viewing experience. For example, the rendering of the HDTV media fragments may be interrupted, jittery or freeze altogether, causing an unsatisfactory viewing experience.

SUMMARY

The inventors have realised the problems associated with the prior art and devised an apparatus and method to mitigate the problems caused by deteriorating network conditions.

According to a first aspect of the invention, there is provided a method of receiving an IPTV channel over a communications network. The method comprises receiving media fragments for a first IPTV channel. A determination is made that network conditions are insufficient to provide the first IPTV channel at a desired quality. As a result of the determination, the media fragments for a second IPTV channel are requested, such that the second IPTV channel provides the same media content as the first IPTV channel but at a quality that requires a lower bandwidth than the first IPTV channel. An advantage of the method is that in the event of deterioration in network conditions, media channels can still be shown without a significant deterioration in a viewer's experience.

As an option, the first channel provides High Definition (HD) media fragments and the second channel provides Standard Definition (SD) media fragments. HD media fragments require a greater bandwidth than SD media fragments, and so by moving from a HD channel to an SD channel showing the same media, less bandwidth is required.

As a further option, the first channel provides media fragments containing frames encoded using a difference codec to the second media channel. The codec used for the second media channel reduces the bandwidth required. Examples of codecs include the first channel being encoded using SD-MPEG2, and the second channel being encoded using SD-MPEG-4; the first channel being encoded using HD-MPEG2, and the second channel being encoded using SD-MPEG-4 (this will give a very large reduction in bandwidth required); and first channel being encoded using SD- MPEG2+AC3, and the second channel being encoded using SD-MPEG-2 Stereo. Of course, many different combinations of codec might give a change in required bandwidth.

As a further option, the first channel provides a greater number of media frames than the second channel, which will also reduce the required bandwidth. The second channel may, for example, have a reduced key-frame rate in the media stream, or alternatively the second channel may have B-frames introduced in a media stream that is shown in the first channel using only l-frames and P-frames.

In an optional embodiment of the invention, the communications network is a Peer to Peer communications network, although the invention may also be applied to a client/server type of network.

The method optionally further comprises stopping requesting media fragments for the first IPTV channel once media fragments are requested for the second IPTV channel. This has the advantage of reducing redundant signalling and preserving available bandwidth.

There are several ways in which the determination that the network conditions have deteriorated. One way is to receive from a remote node a message containing information about the network conditions. A further way is to compare of a rate of receipt of media fragments and a required rate of rendering the media fragments. Another way is to base the determination on a number of lost media fragments.

The method optionally comprises determining that network conditions are adequate to provide the first IPTV channel at the desired quality, and as a result of the determination, requesting media fragments for the first IPTV channel. This allows reversion to the first IPTV channel when the network quality is sufficient to provide the first IPTV channel.

As an option, the method comprises reverting to the first IPTV channel after a predetermined time has elapsed from requesting media fragments for the second IPTV channel. In this way, no determination of the network conditions need be made, and reversion to the first IPTV channel occurs after a specified time. Of course, if conditions have not sufficiently improved then the method allows for switching back to the second IPTV channel.

According to a second aspect of the invention, there is provided a node for use in an IPTV communications network. The node comprises a receiver for receiving media fragments from a first IPTV channel, and a determining function for determining that network conditions are insufficient to provide the first IPTV channel at a desired quality. A transmitter is also provided for requesting media fragments for a second IPTV channel, the second IPTV channel providing the same media content as the first IPTV channel at a quality that requires a lower bandwidth than the first IPTV channel. This allows the node to revert to a channel that requires lower bandwidth is the available bandwidth is insufficient to provide the first IPTV channel at a desired quality.

The node is optionally selected from one of a Set Top Box and a proxy node arranged to act on behalf of a Set Top Box, as these nodes are most commonly used in an IPTV communications network. As an option, the node comprises receiving means for receiving from a remote node a message containing information about the network conditions. This information can be used by the determining function of the node to determine whether network conditions are adequate to provide the first IPTV channel.

The determining function is optionally arranged to make the determination based on a comparison of a rate of receipt of media fragments with a required rate of rendering the media fragments. Alternatively, the determining function is arranged to make the determination based on a number of lost media fragments.

As an option, the determining function is arranged to determine that network conditions are adequate to provide the first IPTV channel at the desired quality and, as a result of the determination, initiate a request for media fragments for the first IPTV channel. This allows the node to revert to the first IPTV channel when network conditions allow for this.

Optionally, the determining function is arranged to request for media fragments for the first IPTV channel after a predetermined time has elapsed since requesting media fragments for the second IPTV channel. This allows the node to revert to the first IPTV channel after a certain time, and therefore does not require the node to make any further determinations about the network conditions. Of course, it may be that network conditions are not yet adequate to provide the first IPTV channel at the desired quality, in which case the node can once more switch to the second IPTV channel.

According to a third aspect of the invention, there is provided apparatus for use in receiving media over a communications network, the apparatus comprising means for performing the method described above in the second aspect of the invention.

According to a fourth aspect of the invention, there is provided a program for controlling an apparatus to perform the method described above in the second aspect of the invention.

According to a fifth aspect of the invention, there is provided a program which, when loaded into an apparatus, causes the apparatus to become an apparatus as described above in the third aspect of the invention. According to a sixth aspect of the invention, there is provided a program described above in either of the fourth or fifth aspects of the invention, carried on a carrier medium. The carrier medium is optionally a storage medium.

According to a seventh aspect of the invention, there is provided a storage medium containing a program as described above in either of the fourth or fifth aspects of the 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 buffer in a STB containing data fragments;

Figure 4 illustrates schematically in a block diagram a media injector and two Set Top Boxes;

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

Figure 6 illustrates schematically in a block diagram the signalling required to initiate an IPTV broadcast with a further Set Top Box;

Figure 7 illustrates schematically in a block diagram keep alive messages sent by a Set Top Box;

Figure 8 illustrates schematically the contents of a buffer where a user is viewing a HDTV channel;

Figure 9 illustrates schematically the contents of a buffer where a user is viewing a SDTV channel; Figure 10 is a flow diagram illustrating the steps according to an embodiment of the invention; and

Figure 1 1 illustrates schematically in a block diagram a node for use in a network according to an embodiment of the invention.

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.

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 sends media data but does not receive media data from the peers. This is illustrated in Figure 4, which is a schematic representation of a simple IPTV P2P network 1. The network 1 includes an IPTV server 6 and two STBs STB1 and STB2. Each STB includes a P2P network interface 2, 3 to which is connected a video decoder 9, 1 1. In this example, STB1 receives the IPTV media stream from both STB2 and the IPTV Server 6, which injects either streaming content 4 or content from a database 7 using a P2P media injector 8. Note that other network nodes (in addition to STBs) may be peers in the network.

Figure 5 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 2 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 P2P function 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 termed STBO. The P2P function 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), and sends a peer list and an IPTV media stream comprising fragments of frames to the P2P network interface of STB1. The P2P network interface of STB1 sends the frames to the video decoder 9 in STB1 , which can then show the IPTV media stream to the user.

Figure 6 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 a P2P network interface in STB2. The P2P network interface 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 P2P function 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 P2P network interface in STB2, which passes the frames of the IPTV media stream to the video decoder.

It is advantageous for all peers in the P2P network to send each other "keep alive" messages, as illustrated in Figure 7, 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 any kind of 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 buffers in each STB and the time it takes to establish communication between peers. The term "media stream" need not necessarily refer to the media data injected into the network by a media injector, but can also be used to refer to media data received from other peers in a P2P network.

Referring to Figure 8, there is illustrated schematically a buffer in a STB, when the STB is receiving a HDTV media stream Channel XJHD. Each numbered box represents a fragment of the HDTV media stream stored in the buffer. If network conditions deteriorate, then some fragments may be missing, which has a negative effect on the quality of the media stream when rendered by the STB. There are several ways in which an STB can determine that network conditions have deteriorated. For example, one way to determine that network conditions have deteriorated is for a remote entity that monitors network conditions to inform the STB that network conditions have deteriorated. A further way is for the STB to determine that it is not receiving the fragments at the required speed in order to correctly render the media frames contained in the fragments. Another way to make the determination is to measure a number of lost fragments. In a P2P network, this function may be performed by a P2P logic function at the STB. Note also that whilst this description refers to an STB receiving the media fragments, it could equally apply to a proxy node receiving fragments on behalf of one or more STBs.

When it has been determined that the network conditions have deteriorated to the point where the STB cannot receive the necessary fragments for the HDTV media stream, the P2P logic function in the STB attempts to find a lower quality channel that requires less bandwidth showing the same media. This can be achieved by requesting to join the same channel, and adding the suffix "_SD" to the end of the channel name in the request. In this example, Channel X_SD is found that shows Channel X in Standard Definition rather than High Definition. Figure 5 herein illustrates the signalling required to join a channel. As illustrated in Figure 9, the buffer contains fewer SDTV fragments than HDTV fragments, because the SDTV media stream includes the same media as the HDTV media stream but at a lower quality, and so fewer fragments are required to render the SDTV media stream.

The user will then view the SDTV media stream instead of the HDTV media stream. This provides better quality media to the viewer than an HDTV media stream with missing fragments, and therefore the deterioration in network quality has a reduced impact on the user's viewing experience. Note that the above description assumes that when the STB requests fragments from Channel X_SD, it requests that no more fragments are received using Channel X_HD. This is necessary in the case that the deterioration in the network is due to a cause close to the network. If the STB were to request fragments from both Channel X_HD and Channel X_SD, then the same problems with bandwidth would occur, and some fragments from Channel X_SD might also be lost. However, note that in some cases it will not be necessary for the STB to stop requesting fragments from Channel X_HD. If, for example, the deterioration in the network occurs close to the media injector for Channel X_HD, then there may be plenty of available bandwidth close to the STB, and so the STB could continue to request fragments for Channel X_HD in addition to requesting fragments from Channel X_SD. Of course, the fragments for Channel X_SD would be shown until the network deterioration is resolved and the STB can revert to Channel X_HD. If the STB receives both channels in parallel, and shows Channel X_SD, it can use the received media fragments for Channel XJHD to monitor the network conditions and assist in determining when to revert back to Channel X_HD.

The user expects a High Definition media stream, and so the STB reverts to receiving HDTV media fragments when network conditions have improved sufficiently to allow the fragments to be sent. There are different triggers that allow an STB to revert to the HDTV channel. In one embodiment, the STB reverts to the HDTV channel after a predetermined time has elapsed. Of course, in this embodiment, the STB has no way of knowing whether the network conditions are adequate to receive the HDTV media fragments until it reverts to the HDTV channel. Once the STB has reverted to the HDTV channel, if it is determined once more that the network conditions are still not adequate for receiving the HDTV media fragments then the STB will revert back to the SDTV channel. Alternatively, the STB could be informed by a remote network entity that monitors network conditions that the network conditions are now adequate for receiving the HDTV media fragments. The STB rejoins the HDTV channel using the signalling illustrated in Figure 5.

In order to summarize an embodiment of the invention, Figure 10 is a flow diagram showing steps of the embodiment. The following numbering refers to the numbering in Figure 10.

51. The STB is receiving high required bandwidth (in this example, HDTV) channel fragments.

52. It is determined that the network conditions have deteriorated such that the HDTV channel may not be rendered at a sufficient quality.

53. The STB requests and receives lower required bandwidth channel fragments (e.g. SDTV), and renders these. There are two options for the STB to revert to the higher required bandwidth channel, as described in steps S4 and S5 below. 54. In one embodiment, the STB determines that network conditions are now acceptable for receiving high bandwidth channel fragments. This may be effected by receiving a message from a remote node that monitors network conditions.

55. In an alternative embodiment, the STB allows a predetermined time to elapse for receiving lower required bandwidth fragments.

56. After the predetermined time has elapsed, or the STB has determined that network conditions are acceptable for receiving the high required bandwidth channel fragments, the STB requests high required bandwidth channel fragments and reverts to rendering the high required bandwidth channel. Steps S1 to S6 may repeat if network conditions deteriorate again.

Referring to Figure 1 1 , there is illustrated a node for use in a network according to an embodiment of the invention. In one embodiment, the node 12 is a STB for use in a P2P network, and comprises a P2P function 13 for handling signalling and data handling. The node 12 comprises a transmitter 14 for transmitting requests for a channel, and a receiver 15 for receiving media fragments. A buffer 16 is provided for storing media fragments, and the fragments are passed to a media renderer 17 for rendering when required.

The above description discusses an embodiment of the invention applied to a STB in a P2P IPTV network. However, it will be apparent that the invention can also apply to a client/server network in which the STB receives the HDTV channel fragments from a media source server.

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 method of receiving an IPTV channel over a communications network, the method comprising: receiving media fragments for a first IPTV channel; determining that network conditions are insufficient to provide the first IPTV channel at a desired quality; as a result of the determination, requesting media fragments for a second IPTV channel, the second IPTV channel providing the same media content as the first IPTV channel at a quality that requires a lower bandwidth than the first IPTV channel.

2. The method according to claim 1 , wherein the first channel provides High Definition media fragments and the second channel provides Standard Definition media fragments.

3. The method according to claim 1 or 2, wherein the first channel provides media fragments containing frames encoded using a difference codec to the second media channel.

4. The method according to claim 1 , 2 or 3, wherein the first channel provides a greater number of media frames than the second channel.

5. The method according to any one of claims 1 to 4, wherein the communications network is a Peer to Peer communications network.

6. The method according to any one of claims 1 to 5, wherein the determination comprises receiving from a remote node a message containing information about the network conditions.

7. The method according to any one of claims 1 to 5, wherein the determination is made based on a comparison of a rate of receipt of media fragments and a required rate of rendering the media fragments.

8. The method according to any one of claims 1 to 5, wherein the determination is made based on a number of lost media fragments.

9. The method according to any one of claims 1 to 8, further comprising: determining that network conditions are adequate to provide the first IPTV channel at the desired quality; and requesting media fragments for the first IPTV channel.

10. The method according to any one of claims 1 to 8, further comprising, after a predetermined time has elapsed from requesting media fragments for the second IPTV channel, reverting to the first IPTV channel by requesting media fragments for the first IPTV channel.

1 1. A node for use in an IPTV communications network, the node comprising: a receiver for receiving media fragments from a first IPTV channel; a determining function for determining that network conditions are insufficient to provide the first IPTV channel at a desired quality; a transmitter for requesting media fragments for a second IPTV channel, the second IPTV channel providing the same media content as the first IPTV channel at a quality that requires a lower bandwidth than the first IPTV channel.

12. The node according to claim 1 1 , wherein the node is selected from one of a Set Top Box and a proxy node arranged to act on behalf of a Set Top Box.

13. The node according to claim 11 or 12, further comprising receiving means for receiving from a remote node a message containing information about the network conditions.

14. The node according claim 11 or 12, wherein the determining function is arranged to make a determination based on one of a comparison of a rate of receipt of media fragments with a required rate of rendering the media fragments, and a number of lost media fragments.

15. The node according to any one of claims 11 to 14, wherein the determining function is arranged to determine that network conditions are adequate to provide the first IPTV channel at the desired quality and, as a result of the determination, initiate a request for media fragments for the first IPTV channel.

16. The node according to any one of claims 11 to 15, wherein the determining function is arranged to request media fragments for the first IPTV channel after a predetermined time has elapsed since requesting media fragments for the second IPTV channel.

17. An apparatus for use in receiving media over a communications network, the apparatus comprising means for performing the method as claimed in any one of claims 1 to 10.

18. A program for controlling an apparatus to perform a method as claimed in any one of claims 1 to 10.

19. A program which, when loaded into an apparatus, causes the apparatus to become an apparatus as claimed in claim 17.

20. A program as claimed in claim 18 or 19, carried on a carrier medium.

21. A program as claimed in claim 20, wherein the carrier medium is a storage medium.

22. A storage medium containing a program as claimed in any one of claims 18 to 20.