GB2481529A

GB2481529A - Congestion control for streaming data

Info

Publication number: GB2481529A
Application number: GB1110590.5A
Authority: GB
Inventors: Edward Hall
Original assignee: Vodafone IP Licensing Ltd
Current assignee: Vodafone IP Licensing Ltd
Priority date: 2010-06-22
Filing date: 2011-06-22
Publication date: 2011-12-28
Also published as: GB201010456D0; GB201110590D0

Abstract

In a wireless network for streaming video media content 2 to mobile users adaptively by reducing quality in busy periods, a Media Presentation Description (MPD) comprising alternative representations of the stream (audio only, video + subtitles etc.) is modified by a network element 6 (eg. a firewall, proxy or cache server), before being presented to the client 4. The modification may comprise removing or replacing the highest bit-rate alternatives in the list, based on network variable 7 such as congestion or whether the user is a subscriber or the alternative has been blacklisted.

Description

CONGESTION CONTROL FOR STREAMING DATA

Field of the Invention

The invention relates to congestion control for streaming data. In particular the invention relates to network-initiated congestion control in adaptive HTTP Streaming (AHS) within a mobile telecommunications network.

Background to the Invention

As the capability of IP networks and network infrastructure has increased, and the quality of Internet-based video streaming technology has improved, the popularity of Internet streaming for video distribution has increased tremendously.

One common method of implementing streaming video is transmitting the video program from a Hypertext Transfer Protocol (HTTP) server to a web-based HTTP client.

From a network management perspective, increased use of video and media streaming combined with terminals capable of rendering higher quality video and media streams, can cause considerable data traffic congestion problems.

Empirical observations from live data show that in most established markets over-the-top (OTT) video accounts for a significant proportion of all traffic directed via the Internet APN (Access Point Name) over mobile telecommunications network.

Typically, this traffic is not charged for, other than by volume on data plans. Yet this traffic is also of such volume that it contributes heavily to congestion within telecommunications networks, in particular mobile/cellular networks.

It is understood that away to reduce the problem of congestion caused by the transmission of video and other media content is to reduce the size of the media, which can be achieved by compression or reducing the quality of the media. It is possible to compress or reduce the bandwidth of video traffic, as terminals are capable of consuming all levels of quality lower than the maximum advertised by said terminal. These compressions and reductions can be of little perceptible difference to the original when observed on a mobile device.

A known solution to this problem is called Adaptive streaming.

Adaptive streaming is a process that adjusts the quality of a video delivered to a web page based on changing network conditions to ensure the best possible viewer experience.

The 3GPP Working Group SA4 (Technical Specification Group (TSG) for Service and System Aspect: Codec) have standardized adaptive HTTP Streaming (AHS) for use in the mobile ecosystem [in 3GPP Release 9 of the PSS standard (TS 26.234), finalized in March 2010. This service is typically used in the fixed-line Internet.

During the initiation of an AHS session, a terminal, or HTTP Streaming Client, requests a media service from a streaming server. The server responds with a Media Presentation Description (MPD) file containing, amongst other items, a list of supported Alternative Representations. Each Alternative Representation consists of one or more media streams (e.g. audio only, video & audio, video, audio & subtitles) The terminal then selects one Alternative Representation of at least one of the media streams based on the information included in the MPD, and requests the selected Alternative Representation from the streaming server.

A problem with adaptive HTTP streaming as defined in Release 9 of the PSS standard is that is relies on the streaming client to select the most appropriate media stream. There are also a number of network-based factors which could also be taken into consideration when selecting a media stream, for example: network congestion, data usage allowances of the streaming client, and priority of the streaming client.

Summary of the Invention

Against this background, the present invention provides a system for streaming media content, the system comprising: a streaming media server arranged to send a media presentation description (MPD) via a communications network to a media client terminal, the MPD describing media content comprising alternative representations of one or more media types; and a network element located the communications network in the data path between the transmission of the MPD from the streaming media server and receipt of the MPD at the media client terminal, the network element comprising: a processor arranged to read at least part of the MPD; means for modifying at least part of the MPD; and means for sending the modified MPD to the media client terminal.

Preferably the network element is arranged to receive input from one or more network variables, and the means for modifying the MPD comprises means to modify the MPD based on the data of said received one or more network variables.

Preferably, the means for modifying the MPD comprises means for removing one or more of the highest bit-rate alternative representations from the MDP.

Alternatively, the means for modifying the MPD may comprise means for adding one or more network selected alternative representations to the MDP.

In a further alternative, the means for modifying the MPD may comprise means for replacing one or more alternative representations in the MDP with one or more network selected alternative representations.

Preferably at least one of the one or more network variables comprises a measure of the operating state of the communications network.

Alternatively, the at least one of the one or more network variables may comprise data relating to the network subscription plan associated with the media client terminal.

In one advantageous embodiment, the one or more of the network variables comprise a black-list of alternative representations, and said network element is arranged to remove an alternative representation from the MPD if it matches an alternative representation on the black-list.

The present invention also provides a corresponding method comprising: sending a media presentation description (MPD) via a communications network from a streaming media server to a media client terminal, the MPD describing media content comprising alternative representations of one or more media types; intercepting the MPD in communications network data path between the transmission of the MPD from the streaming media server and receipt of the MPD at the media client terminal; reading at least part of the intercepted MPD; modifying at least part of the read MPD; and sending the modified MPD to the media client terminal.

Brief Description of the Drawings

The invention may be put into practice in various ways, a number of which will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a schematic illustration of the system architecture for Adaptive HTTP streaming according to the

prior art; and

Figure 2 shows a schematic illustration of an embodiment of the present invention.

Detailed Description of Preferred Embodiments

Adaptive HTTP Streaming (AHS) The 3GPP Adaptive HTTP Streaming protocol provides a streaming service. Figure 1 shows the system architecture for Adaptive HTTP streaming. This enables delivering content from a content preparation system 1 via one or more standard HTTP Server(s) 2 to an HTTP-Streaming Client 4 and enables caching content by standard SlIP caches 3. SlIP streaming is defined as the interface 5 between the HTTP Streaming Client and the HTTP Streaming Server.

It is assumed that the HTTP Streaming Client has access to a Media Presentation Description (MPD) . An MPD provides sufficient information for the HTTP Streaming Client to provide a streaming service to the user by sequentially downloading media data from an HTTP server and passing the included media to a rendering engine appropriately.

To initiate the streaming service to the user, the HTTP Streaming Client establishes a media presentation by downloading the relevant metadata and subsequently the media data.

Media Presentation A media presentation is a structured collection of data that is accessible to the HTTP Streaming Client 4. The HTTP Streaming client 4 requests and downloads media data information to present the streaming service 2 to the user.

A media presentation is described in a Media Presentation Description (MPD) . The MPD and all attributes and elements are provided in clause 12.2.5 of 3GPP TS 26.234.

A media presentation consists of * A sequence of Periods.

* Each Period contains one or more Representations from the same media content.

* Each Representation consists of one or more segments.

* Segments contain media data and/or metadata to decode and present the included media data.

The media presentation has a time line that is defined by the concatenation of the timeline of each period. The timeline in each period is common to all representations.

The media presentation may be of type On-Demand or Live. The MPD attribute type provides the type of the media presentation.

If the attribute duration is provided, the MPD describes an entire media presentation.

The MPD attribute duration describes the duration of the media presentation. For type Live, if the MPD attribute duration is provided in the MPD, then the sum of the duration attribute and MPD attribute availabilityStart specifies the end time of the media presentation. If the attribute duration is not provided, then the MPD does not describe an entire media presentation and the MPD may be updated according to the procedures specified in 12.2.5.4 of 3GPP TS 26.234.

MPD Modifier The MPD is sent from the HTTP Streaming Server 2 to the HTTP Streaming Client 4 in clear text and not encrypted. For any given session either ongoing in a cell or requested to be started in a cell, the MPD can thus be identified.

As a result, any network element in the path of the data flow (e.g. firewall, GGSN, deep packet inspection node, HTTP Proxy, cache server, etc.) may be configured to read and, where required, modify the MPD. Alternatively a new network element can be included in the path of the data flow between the HTTP Streaming Sever 2 and the HTTP Streaming Client 4. For the purpose of this description, and with reference to Figure 2, this network element is referred to as the MPD Modifier 6.

Typically the MDP Modifier 6 is arranged to remove the higher bit-rate Alternative Representations from the MDP (which are considered to have the highest cost to the network in terms of load), therefore lowering the upper limit of the bandwidth consumable in the service.

The MDP Modifier 6 preferably receives input form one or more network variables 7. The network variable 7 may be any single, or combination of any variables which can be measured or determined by the network operator. The network variable 7 will typically be either: a) a measure of the operating state of the network, for example network congestion, network load, network traffic shaping; and/or b) a variable dependent on the HTTP Streaming Client 4 or its user, for example a premium service plan may allow a user to access higher guality media streams, or a user may be approaching (or have reached) their permitted data guota in which case they may be restricted to retrieving lower guality media streams.

In a further aspect of the invention, the MPD Modifier 6 may be arranged to add additional Alternative Representations to the MDP, or augment the MDP with other date, for example: a) inserting a guideline bandwidth that should be targeted by the I-ITTP Streaming Client; b) marking certain alternative representations as less desirable in a negotiation; and/or c) marking higher bandwidth representations as less critical to the service, therefore increasing their likelihood to be abandoned in case of bandwidth starvation.

In yet further aspects of the invention, modification of the MPD in transit from the HTTP Streaming Server 2 to the HTTP Streaming Client 4 may be used to accomplish other technical

goals, for example:

* adding an Alternative Representation for inserting an advertisement; * adding Network Operator branding to a stream, for example, through a Timed Graphics "channel bug" overlay; * replacing audio streams with Timed Text streams for users known to be audio-impaired; * adding lower quality Alternative Representations than those offered originally to allow lower-rate adaption * removing Alternative Representations based on non-typical languages (e.g. Spanish in francophone markets) . This could be dependent on the geographical location of the HTTP Streaming Client 4 or the user account and/or preferences of the HTTP Streaming Client 4; and/or * compression of MDP data using the XPATH method, with resolution provided by the modifying entity In a final aspect of the invention, the MDP Modifier 6 may be arranged to detect and remove Alternative Representations which are identified on a black-list connected to the MDP Modifier 6.

Claims

CLAIMS1. A system for streaming media content, the system comprising: a streaming media server arranged to send a media presentation description (MPD) via a communications network to a media client terminal, the MPD describing media content comprising alternative representations of one or more media types; and a network element located the communications network in the data path between the transmission of the MPD from the streaming media server and receipt of the MPD at the media client terminal, the network element comprising: a processor arranged to read at least part of the MPD; means for modifying at least part of the MPD; and means for sending the modified MPD to the media client terminal.
2. The system of claim 1, wherein the network element is arranged to receive input from one or more network variables, and the means for modifying the MPD comprises means to modify the MPD based on the data of said received one or more network variables.
3. The system of claim 1 or claim 2, wherein the means for modifying the MPD comprises means for removing one or more of the highest bit-rate alternative representations from the MDP.
4. The system of claim 1 or claim 2, wherein the means for modifying the MPD comprises means for adding one or more network selected alternative representations to the MDP.
5. The system of claim 1 or claim 2, wherein the means for modifying the MPD comprises means for replacing one or more alternative representations in the MDP with one or more network selected alternative representations.
6. The system of any of claims 2 to 5, wherein the at least one of the one or more network variables comprises a measure of the operating state of the communications network.
7. The system of any of claims 2 to 5, wherein the at least one of the one or more network variables comprises data relating to the network subscription plan associated with the media client terminal.
8. The system of any of claims 2 to 5, wherein the one or more of the network variables comprise a black-list of alternative representations, and said network element is arranged to remove an alternative representation from the MPD if it matches an alternative representation on the black-list.
9. The system of any preceding claim, wherein the network element comprises one or more of: a firewall, a GGSN, a deep packet inspection node, an HTTP Proxy, or a cache server
10. A method comprising: sending a media presentation description (MPD) via a communications network from a streaming media server to a media client terminal, the MPD describing media content comprising alternative representations of one or more media types; intercepting the MPD in communications network data path between the transmission of the MPD from the streaming media server and receipt of the MPD at the media client terminal; reading at least part of the intercepted MPD; modifying at least part of the read MPD; and sending the modified MPD to the media client terminal.
11. The method of claim 10, wherein the network element is arranged to receive input from one or more network variables, and the step of modifying at least part of the MPD comprises modifying the MPD based on the data of said received one or more network variables.
12. The method of claim 10 or claim 11, wherein the step of modifying the MPD comprises removing one or more of the highest bit-rate alternative representations from the MDP.
13. The method of claim 10 or claim 11, wherein the step of modifying the MPD comprises adding one or more network selected alternative representations to the MDP.
14. The method of claim 10 or claim 11, wherein the step of modifying the MPD comprises replacing one or more alternative representations in the MDP with one or more network selected alternative representations.
15. The method of any of claims 11 to 14, wherein the at least one of the one or more network variables comprises a measure of the operating state of the communications network.
16. The method of any of claims 11 to 14, wherein the at least one of the one or more network variables comprises data relating to the network subscription plan associated with the media client terminal.
17. The method of any of claims 11 to 14, wherein the one or more of the network variables comprise a black-list of alternative representations, and including the step of removing an alternative representation from the MPD if it matches an alternative representation on the black-list.
18. A system as substantially hereinbefore described and with reference to Figure 2.
19. A method as substantially hereinbefore described and with reference to Figure 2.
20. A computer program operable to carry out the method of any of claims 10 to 17.*::r: INTELLECTUAL . ... PROPERTY OFFICE Application No: GB 1110590.5 Examiner: Dr Mark Lewney Claims searched: 1-20 Date of search: 27 September 2011 Patents Act 1977: Search Report under Section 17 Documents considered to be relevant: Category Relevant Identity of document and passage or figure of particular relevance to claims X,E 1-3,5,6, W02011/087449 Al 9-12, 14 (ERICSSON) -See especially figs 1, 2 & 9 and accompanying& 15 description.A,E -W02011/053658 Al (QUALCOMM) -See especially paragraphs [0024-25, 0034-44 & 0075].A,E -GB2476271 A (SKYPE) -Consider whole document.Categories: X Document indicating lack of novelty or inventive A Document indicating technological background and/or state step of the art.Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of before the filing date of this invention.same category.& Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB, EP. WO & US patent documents classified in the following areas of the UKCX Worldwide search of patent documents classified in the following areas of the IPC HO4L The following online and other databases have been used in the preparation of this search report WPI, EPODOC, Google.International Classification: Subclass Subgroup Valid From HO4L 0029/06 01/01/2006 HO4L 0029/08 01/01/2006 HO4N 0007/24 01/01/2011 Intellectual Property Office is an operating name of the Patent Office www.ipo.gov.uk