WO2018002469A1

WO2018002469A1 - Method and device for managing a session for transmitting a video stream

Info

Publication number: WO2018002469A1
Application number: PCT/FR2017/051558
Authority: WO
Inventors: Gaël FROMENTOUX; Frédéric FIEAU
Original assignee: Orange
Priority date: 2016-06-30
Filing date: 2017-06-15
Publication date: 2018-01-04
Also published as: FR3053556A1

Abstract

The method according to the invention for managing a session for transmitting a video stream between a content server and a terminal via a telecommunications network comprises, following the detection (F10) of the start of the session: - a step (F50) of obtaining information representing conditions for transmitting the video stream that are experienced on the network during the session; and - if said transmission conditions are not considered to be favourable (F60): o a step (F90) of obtaining a current state of a buffer used by a reproduction module of the terminal for reproducing the video stream and representing a filling level of the buffer; and o a step (F110) of selecting at least one prioritisation policy to be applied to the transmission of the video stream to the terminal so that the transmission session is located within a start period in respect of a predetermined criterion and so that the filling level of the buffer is below a predetermined filling threshold.

Description

Method and device for managing a transmission session of a video stream

Background of the invention

The invention relates to the general field of telecommunications.

It relates more particularly to the transmission of video streams between a content server and a terminal in a telecommunications network.

Operators of telecommunications networks and content providers, especially video, are now collaborating more and more in order to better match the needs of applications using this content with network capabilities. This includes optimizing delivery of content across networks to improve the quality of service perceived by content provider customers.

An axis of improvement of this quality of service (or experience perceived by the customers) targeted specifically by the content providers consists in particular in reducing the latency observed between the service request made by a client to a server. content to access a video stream and the viewing by this client of the first images of the video stream. The constraint imposed by the content providers is that the client does not wait too long to start watching the video stream he has requested, otherwise he will become demotivated and abandon his communication session with the content server. No limitation is attached to the nature of the service accessed by the customer to view the stream: it can be indifferently a video-on-demand service, web browsing, streaming real-time streaming etc.

This constraint is all the more critical when the client accesses the content server via a mobile telecommunications network, such as for example a cellular network (for example the 4G network - Fourth Generation) or a WiFi network (WIreless FIdelity), whose the transmission conditions can fluctuate according to various parameters (environment, mobility, cell load, etc.).

Object and summary of the invention

The invention makes it possible in particular to respond to this problem by proposing a method of managing a transmission session of a video stream between a content server and a terminal via a telecommunications network, this management method comprising, following a detection of a session start:

A step of obtaining information representative of transmission conditions of the video stream experienced during the session on the network;

- if the said conditions of transmission are not considered favorable:

a step of obtaining a current state of a buffer used by a rendering module of the terminal for the rendering of the video stream and representative of a filling level of the buffer; and o a step of selecting a prioritization policy to be applied to the transmission of the video stream to the terminal as long as the transmission session is in a start-up period with regard to a predetermined criterion and the filling level of the buffer is less than a predetermined filling threshold. Correlatively, the invention also relates to a device for managing a transmission session of a video stream between a content server and a terminal via a telecommunications network, this management device comprising:

A module for detecting a start of the session;

A first obtaining module, activated on detection of a start of the session by the detection module and configured to obtain information representative of transmission conditions of the video stream experienced during the session on the network;

Modules activated if said transmission conditions are not considered favorable by the first obtaining module comprising:

a second obtaining module, configured to obtain a current state of a buffer used by a rendering module of the terminal for the rendering of the video stream and representative of a filling level of the buffer; and

a selection module, configured to select at least one prioritization policy to be applied to the transmission of the video stream to the terminal as long as the transmission session is in a start-up period with regard to a predetermined criterion and the level filling of the buffer is less than a predetermined filling threshold.

The modules of the management device can be located for example in a PoP (Point of Presence) access point to the network of the operator.

In order to reduce the latency at the start of the rendering of a video stream on a user's terminal, the invention proposes to temporarily prioritize the data relating to this video stream when the video transmission session is experimenting with unfavorable transmission conditions on a video stream. the network (for example a too large load on the cell to which the terminal is attached for a cellular network, or a bad radio reception due for example to a bad positioning of the terminal in the cell) and is therefore likely to be affected by a high latency. By prioritizing, here is meant to give preferential importance to these data, in other words to promote their transmission to the terminal with respect to the data of other video streams.

This temporary prioritization is applied as long as the transmission session is in a start-up period and as long as a buffer used by a rendering module (also commonly referred to as "player") of the terminal during the playback of the video stream. reached a satisfactory fill level to ensure a restitution of the video stream to the user of the terminal. The inventors have indeed connected the state of this buffer to the latency experienced by the terminal at the beginning of the video session: if the terminal has gathered enough data concerning the video stream in this buffer (in other words, if the filling level of this buffer is greater than a given filling level), we can expect a fast and correct visualization of the flow by the user on his terminal, so there is no need to intervene. On the other hand, if the filling level of the buffer is insufficient at any point in the start-up period, the invention proposes to remedy this situation, which can be unacceptable for the user of the terminal by prioritizing the data of the flow. video intended for the terminal. In this way, it is anticipated that the user may have difficulty in accessing the content of the video stream that he has requested.

The conditions for stopping the prioritization (start-up period and insufficient filling level of the buffer) advantageously make it possible to focus on the start of the session and on the real needs of the user of the terminal. For example, the video stream transmission session is considered to be in a start period if a period of time since the start of the transmission session is less than a predetermined maximum period or if a quantity of data related to the video stream issued by the content server is less than a predetermined maximum quantity.

The invention makes it possible to give priority to certain video streams without disrupting the simultaneous transmission of other video streams on the network to other users. The prioritization proposed by the invention is indeed not intended to last longer than necessary or to apply when the transmission conditions experienced by the terminal do not justify it (eg favorable radio propagation conditions and / or buffer used by the playback module (player) sufficiently filled to allow access to the fast video stream by the user).

By thus reducing the latency at the start of the rendering of a video stream, the invention makes it possible to improve the experience perceived by the user and to avoid the abandonment of sessions lamented to the users in case of slow start restitution.

In a particular embodiment, the current state of the buffer is obtained from a signaling message sent by the terminal in a signaling session established with the content server for the transmission session of the video stream.

The signaling message and the signaling session are for example in accordance with the protocol SPUD (Session Protocol for User Datagrams). The SPUD protocol is only an example and it is possible to use other cooperation protocols between end devices (content servers, user terminals) and intermediate equipment able to modify or inspect the data traffic. (eg DPI).

The SPUD protocol is a protocol currently being standardized by the IETF (Internet Engineering Task Force, documents "draft-trammell-spud-req-04" and "draft-hildebrand-spud-prototype-03"), implementing collaboration among Internet players, including telecommunication network operators and content providers. This protocol is intended to broadcast messages, also called "advices", carrying recommendations related to both the services and the network. In particular, it allows end devices (eg client terminals or content servers here) to exchange advices with other intermediate network equipment through which data travels to adapt the behavior of these devices to the constraints of the applications. activated on end equipment. Such intermediate equipment is here for example the management device according to the invention. It is noted that according to the SPUD protocol, signaling sessions are established outside the transmission sessions to which they are attached (ie they are separate sessions), once the transmission sessions have been established between the protagonists (ie terminal and content server).

The invention therefore takes advantage, in this embodiment, of the existence of this protocol and its many possibilities for conveying to the device for managing information on the terminal and more particularly on the state of the buffer used by the device. player of the terminal for the restitution of the video stream. The management device is here an intermediate equipment between the terminal and the content server, but thanks to the SPUD protocol, can access various information conveyed between the terminal and the content server, even if the content server is not under the control of the network operator. The invention therefore takes advantage of the developments proposed today for web applications to obtain various information to optimize the start of a video stream transmission session and promote communications between applications and network.

It is noted that the protocol SPUD, in its current version as specified by I1ETF, does not include options for reassembling information from the terminal to the content server relating to a physical state of the terminal, such as for example the level of filling of the buffer used by the player of the terminal for the restitution of the flow. The invention therefore proposes to enrich the current signaling proposed by the SPUD protocol with new options making it possible to optimize the provision of video content, this protocol being particularly suitable for the implementation of the invention.

The invention is however not limited to the use of the SPUD protocol for conveying information from the terminal to the management device. Other protocols, such as the HyperText Transfer Protocol (http), can be used alternatively.

In a particular embodiment, the detection of the start of the video transmission session includes a detection of the establishment of the signaling session between the terminal and the content server.

The establishment of the signaling session, especially in the case of the SPUD protocol, is easily detectable and makes it easy to identify that a video transmission session is started.

In a particular embodiment, the method further comprises a preliminary step of determining whether or not the session of transmission of the video stream is a session. so-called collaborative, a prioritization policy being applied to the transmission of the video stream only if the transmission session is a collaborative session.

The invention thus makes it possible to prioritize certain so-called collaborative sessions to the detriment of other non-collaborative sessions. The notion of "collaborative session" depends on a predetermined criterion: it can be for example sessions associated with content providers with which the network operator has agreements, or sessions attached to specific terminals (ex. user terminals with a particular status in the network), to particular users (eg particular identities and / or subscriptions), to a particular domain / subdomain, to particular identifiers (eg IP address), etc. and for which the management device according to the invention preferentially has access to all or part of the signaling exchanged in the signaling session.

Thus, different parameters can be considered to identify whether a session is collaborative or not, depending on the criterion used to define these sessions. For example, if we are interested in content providers strictly speaking, an IP address of the server conveyed in the signaling transmitted by the terminal can be used and confronted with IP addresses attached to servers of content providers with whom a collaboration has been established.

In another embodiment, the steps of obtaining a current state of the buffer and the step of selecting at least one prioritization policy are conditioned by the detection of a valid token in a signaling message sent by the terminal.

Such token may for example include an identifier, possibly encrypted. It can be used to easily identify collaborative sessions for example.

In a particular embodiment, said at least one prioritization policy is selected from at least:

A policy of deleting data transmitted on the network relating to at least one video stream of at least one transmission session established with at least one other terminal;

A policy of deleting data transmitted on the network relating to at least one video stream of at least one transmission session established with at least one other terminal when said at least one transmission session has a latency greater than a threshold of predetermined latency; and

A policy of adapting a transmission speed to the terminal, by an intermediate device between the content server and the terminal, data relating to the video stream of the transmission session as a function of a filling level of a buffer of the intermediate equipment and a throughput of the network experienced by the terminal.

These different prioritization policies make it possible to act quickly on the transmission of data from the video stream intended for the terminal. Indeed, because of the limited period during which the prioritization of the data is applied (start period of the transmission session of the video stream only), a quick and effective response must be provided. The first two aforementioned policies to delete data relating to video streams exchanged in the context of sessions not intended for the terminal make it possible to efficiently use the data of the transmission session of the terminal. The transmission sessions whose data are deleted are, for example, the sessions identified as non-collaborative. The first two policies thus promote sessions of video stream transmission from servers with which collaborations with the network operator have been established or to terminals preferred by the operator. For a mobile telecommunications network such as a cellular network or a 4G network, the deletion of data to be transmitted has an immediate effect on the allocation of resources for the terminal whose flow is sought to be favored, which becomes more favorable. , thereby improving the conditions of transmission of the video stream to the terminal.

It should be noted that the second data deletion policy advantageously takes into account the latency of the sessions in addition to the collaborative or non-collaborative nature of the session. Indeed, the inventors have found that when this latency is too important, it is useless to transmit the data to the terminal having requested them, because it is not able to receive them. This second deletion policy therefore limits the impact of this policy on other users.

The third prioritization policy proposed above is particularly effective and makes it possible not to saturate the link between the terminal and the content server, particularly in the case where several transmission sessions are prioritized simultaneously according to the invention.

Of course, this list is not exhaustive and other policies can be envisaged, such as a combination of all or part of the aforementioned prioritization policies.

In a particular embodiment, said at least one selected prioritization policy is notified in a signaling message sent in the signaling session established with the content server, this signaling message requesting the application of said at least one policy of prioritization selected by at least one intermediate device between the server and the terminal through which the video stream passes.

In a preferred embodiment, the signaling session used to notify said at least one prioritization policy to the equipment participating in the transmission of the video stream is a session compliant with the SPUD protocol and the signaling message used is a "advice" provided by this protocol. . The implementation of the invention is thus greatly facilitated.

Thus, not only the invention proposes to use existing signaling sessions to convey in the network and the various intermediate devices involved in the transmission of the flow between the content server and the terminal of the application information, but these same signaling sessions are also used to notify the prioritization policy selected by the management system and to enforce it. In particular, the signaling session thus established on the sidelines of the transmission session makes it possible for the management device to easily obtain information from the terminal and to easily transmit the decisions taken concerning the prioritization of the data relating to the flow. This is the case, for example, when the equipment (or equipment) strictly applying the prioritization policy selected to the video stream is an intermediate server placed upstream of the access of the terminal to the network or is not under direct control of the network operator. This server may be for example a delivery server or streamer attached to a content distribution network operating on behalf of the content provider or acting as a content provider.

In a particular embodiment, the management method according to the invention comprises a step of updating said at least one prioritization policy during the start period of the transmission session as a function of the current state of the buffer and / or current transmission conditions of the video stream experienced during the session on the network.

Such an update may be related to different factors. For example, the transmission conditions experienced on the network by the video session may have evolved and made inappropriate the selected prioritization policy. According to another example, the state of the buffer may not change as desired and require the adoption of another prioritization policy, etc. The management device according to the invention can be configured to obtain periodically or at predetermined times the information concerning the conditions of transmission of the session and / or the state of the buffer so that it can intervene quickly and adapt its prioritization policy effectively. . Note that this update is performed according to the invention only if one is still in the start period of the session.

In a particular embodiment, the method comprises:

During the application of said at least one selected prioritization policy, at least one step of obtaining information representative of transmission conditions of the video stream experienced during the session on the network; and

A step of interrupting the application of said at least one selected prioritization policy if said transmission conditions are considered favorable.

Thus, the updating of said at least one prioritization policy may also consist of a cessation of the prioritization if it no longer proves necessary. In this way, the impact on the other transmission sessions established on the network of the prioritization of the data of the video stream intended for the terminal is limited.

In a particular embodiment, the various steps of the management method are determined by instructions of computer programs.

Accordingly, the invention also relates to a computer program on an information medium, this program being capable of being implemented in a management device or more generally in a computer, this program comprising instructions adapted to the implementation of the steps of a management method as described above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.

The invention also relates to a computer readable information or recording medium, and comprising instructions of a computer program as mentioned above.

The information or recording medium may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.

On the other hand, the information or recording medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can be downloaded in particular on an Internet type network.

Alternatively, the information or recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

The invention also relates to a communication system comprising:

At least one terminal;

At least one content server capable of supplying a video stream to said terminal during a transmission session established with the terminal; and

A device for managing this transmission session according to the invention; and

At least one intermediate device between the content server and the terminal through which the video stream transits and able to apply a prioritization policy selected by the management device if necessary for said transmission session.

Note that the management device and the intermediate equipment may be, in a particular embodiment, co-located on the same equipment.

It may also be envisaged, in other embodiments, that the management method, the management device and the communication system according to the invention present in combination all or part of the aforementioned characteristics. Brief description of the drawings

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures: FIG. 1 schematically represents a communication system according to the invention, in a particular embodiment, this system comprising a device for managing video flow transmission sessions according to the invention;

- Figure 2 shows schematically the hardware architecture of the management device of Figure 1;

FIG. 3 represents, in the form of a flow chart, the main steps of a method of managing a transmission session of a video stream according to the invention; and

FIG. 4 represents, in the form of a diagram, the signaling messages exchanged during the implementation of the invention.

Detailed description of the invention

FIG. 1 presents, in its environment, a communication system 1 according to the invention, in a particular embodiment.

In this embodiment, the communication system 1 comprises: a terminal 2 of a user U; and

One or more content servers 3 capable of supplying video streams, in particular to the terminal 2. These video streams may be provided by the content servers 3 in the context of various services, such as for example a web browsing service, a service video on demand, a streaming service, etc.

In the example envisaged in FIG. 1, the terminal 2 is a mobile terminal able to communicate on a mobile cellular telecommunications network AN (access network) such as for example a 4G network and on which the user U can visualize video streams transmitted via the mobile network AN. The mobile terminal 2 is equipped for this purpose with a screen 2A and a video rendering module 2B (or video player) comprising a buffer 2C making it possible to collect data relating to the video stream with a view to their continuous rendering on the screen 2A of the terminal 2.

No limitation is however attached to the nature of the network on which the terminal 2 is likely to communicate. It may be an alternative of a WIFI, 3G, etc. network.

The mobile telecommunications network AN comprises, in known manner, one or more base stations for covering the different cells of the network. It is assumed that the mobile terminal 2 is attached to the base station 4.

The mobile network AN is connected here to an IP core network CN via a convergent gateway (gateway operator) or CGW (for Convergent GateWay) 5. In known manner, such a gateway CGW 5 advantageously allows to connect several fixed access networks , WIFI and mobile at the same core IP network. It lies between the mobile network AN and the core network CN, and is located here in an access point 6 at the heart of CN network more commonly referred to as PoP for "Point of Presence". Such a PoP can concentrate in a single technical room different types of equipment intended to interact. In the embodiment described here, the PoP 6 further comprises a delivery server 7 or streamer capable of delivering the video contents hosted by the content servers 3. This delivery server 7 is strictly speaking a cache with a storage buffer of the data it receives, known per se.

The core network CN is connected here to the public Internet network in which the content servers 3 are located. The video streams transit between the content servers 3 and the terminal 2 by routers, including a router R, represented in the network CN for example in Figure 1. In the example envisaged here, the content servers 3 are controlled by an operator separate from the operator of the access network AN and CN core network. However, this hypothesis is not limiting in itself. For example, a content server 3 may very well be in another PoP of the operator of the CN network, following specific agreements with the content provider. In this case the video streams do not need to pass through the public Internet network.

In the remainder of the description, a single network or a network made up of several (sub) networks by which the connections established between the terminal 2 and the content servers are transmitted by the telecommunications network is indifferently denoted by 3 in the Internet. In the example envisaged in FIG. 1, the telecommunications network within the meaning of the invention thus comprises the access network AN, the core network CN and the Internet network. However, no limitation is attached to the composition of this network.

As mentioned above, a critical problem facing telecommunication network operators today, and incidentally the providers of content offering video content to their customers via these networks, is to limit the latency experienced by customers at the start of their network. video streaming sessions. Latency refers to the time elapsing between the moment when the customer chooses a video stream and activates its download on the content server and the moment when the video stream restitution actually starts on the client terminal.

The invention advantageously makes it possible to reduce this latency by prioritizing, under certain conditions, the data relating to the video stream selected by the client during the start-up period of the transmission session of this video stream. For this purpose, the communication system 1 comprises a video stream transmission session management device according to the invention. In the embodiment described here, the management device according to the invention is integrated in the convergence gateway 5, at the level of the PoP 6. In the following description, the management device is therefore also referenced by 5, as the convergence gateway.

In the embodiment described here, the management device 5 has the hardware architecture of a computer, as shown in FIG. 2.

It comprises in particular a processor 8, a random access memory 9, a read-only memory 10, a non-volatile flash memory 11 as well as communication means 12 enabling it to communicate in particular with the terminal 2 on the mobile telecommunications network AN and with CN network core equipment and the Internet, as for example with the content servers 3. Such means are known per se and are not described more in detail here. It should be noted here that these communication means also implement the SPUD protocol, as described in more detail later.

The ROM 10 of the management device 5 constitutes a recording medium according to the invention, readable by the processor 8 and on which is recorded here a computer program PROG according to the invention.

The computer program PROG defines functional and software modules here configured to implement the steps of the method of managing video streaming sessions according to the invention. These functional modules rely on and / or control the hardware elements 8-12 of the management device 5 mentioned above. They include in particular here, as illustrated in FIG.

A detection module 5A for starting a transmission session of a video stream between a content server 3 of the Internet network and a terminal, such as the terminal 2;

A first obtaining module 5B, activated on detection of a start of a transmission session of a video stream by the detection module 4A and configured to obtain information representative of transmission conditions of the video stream experienced during the the session on the network separating the terminal 2 from the content server 3 providing the video stream;

Modules activated if said transmission conditions are not considered favorable by the first obtaining module 5B these modules comprising:

a second obtaining module 5C, configured to obtain a current state of the buffer 2C of the video player 2B used by the terminal 2 for the reproduction of the video stream and representative of a filling level of the buffer; and

a selection module 5D, configured to select a prioritization policy to be applied to the transmission of the video stream to the terminal 2 as long as certain conditions are respected. These conditions are, according to the invention, that the transmission session is in a starting period with regard to a predetermined criterion detailed later and that the filling level of the buffer

2C is less than a predetermined filling threshold noted THR1.

The functions of these different modules are described in more detail now, with reference to FIGS. 3 and 4.

FIG. 3 represents the main steps of the method of managing a transmission session of a video stream according to the invention, such that they are implemented, in a particular embodiment, by the device 5 of management of Figure 1 for managing a transmission session of a video stream required by the terminal 2 from one of the video content servers 3 located in the Internet. This management carried out by the management system 5 is based on on different signaling messages exchanged between the different entities (terminal 2, content server 3, management device 5), further represented in the form of a diagram in FIG. 4.

3-1 denotes the content server from which the terminal 2 requests the obtaining of a video stream, for example via a web portal here. This transmission of video streams between the content server 3-1 and the terminal 2 is framed by a https VIDEO_S transmission session established in a manner known per se between the content server 3-1 and the terminal 2 (step E10 in the figure 4). The video stream transmitted in this session passes via different network equipment, and in particular via the PoP 6.

It is assumed here that following the establishment of the video transmission session

VIDEO_S, a signaling session according to the SPUD protocol is established between the terminal 2 and the content server 3-1. The establishment of such an SPUD session is performed by sending an SPUD OPEN initialization message by the terminal 2 to the content server 3-1 specifying the source (src = terminal 2) and the recipient (dest = server 3-1) (step E20). Content server 3-1 responds to this initialization message via a SPUD ACK message (step E30). This session is designated by SPUD_S.

In a known manner, the signaling session SPUD_S is established in the margin (i.e. in addition) of the transmission session VIDEO_S (it is a separate session of the video session). It allows the exchange of application and network data between the terminal 2 and the content server 3-1. Furthermore, advantageously, the SPUD protocol offers the possibility to intermediate equipment of the network to intercept the messages exchanged in this signaling session SPUD and to access the information that it conveys (when these are not not protected). This is the case in particular for the PoP 6 through which the VIDEO_S transmission session and the associated signaling session SPUD are transmitted, and more particularly for the management device 5 embedded in this PoP 6.

With reference to FIG. 3, the management device 5 thus detects, via its detection module 5A, the start of the transmission session VIDEO_S by detecting the initialization of the signaling session SPUD_S, that is to say say the SPUD OPEN message (step F10).

In an alternative embodiment, the detection module 5A associates a time T1 with the detection of the SPUD OPEN initialization message SPUD_S and a time T2 with the detection of the SPUD ACK acknowledgment message sent by the server 3-1. . The difference between T2 and T1 allows the detection module 5A to have a more accurate estimate of the beginning of the transmission session.

In yet another variant, the beginning of the transmission session can be detected by analyzing the requests and packets from the IP address of the server 3-1.

It is assumed, in the embodiment described here, that only the so-called collaborative transmission sessions are prioritized. By "collaborative" is meant here that an agreement has been established previously between the network operator carrying the transmission sessions and the operator of the content servers 3 for managing the sessions conveying the video streams proposed by the content servers 3 according to the invention. It is assumed here that this agreement allows the management device 5 to be able to access and analyze at least a part of the information conveyed in the SPUD sessions associated with the transmission sessions of the video streams to implement the invention. Similarly, such a service may be offered to users of terminals that may access the content offered by the servers 3. In the embodiment described here, a list COLLABJ. identifying all the content servers (eg via their Internet Protocol (IP) address or other identifier) concerned by the agreement and / or the terminals that have subscribed with the network operator so that their transmission sessions are prioritized if appropriate in accordance with the invention, is stored for example in the nonvolatile memory 11 of the management device 5. This list COLLABJ. therefore groups all the information needed to distinguish collaborative transmission sessions from sessions that are not.

The management device 5 thus analyzes, via here its detection module 5A, the transmission session VIDEO_S and determines whether this session VIDEO_S is a collaborative session or not (test step F20). For this purpose, the detection module 5A extracts certain parameters of the VIDEO_S session such as the IP address of the content server 3-1. Then it compares this IP address to the content server identifiers present in the list COLLAB_L. It is assumed here that the content server 3-1 is identified in the list COLLABJ. (yes answer to test step F20). The detection module 5A concludes that the VIDEO_S session is collaborative.

If the module 5A determines that the session SPUD_S is non-collaborative (answer no to the test step E20), then the management method stops (step F40).

In the embodiment described here, the module 5A then determines whether a valid token (or "token") is present in the SPUD OPEN initialization message of the SPUD session sent to step F20 (test step F30). Detection of this token is used to validate that the VIDEOJ5 transmission session is collaborative.

Such token can be encrypted or not. In the embodiment described here, the detection of a valid token conditions the management of the transmission session VIDEOJ5 associated with the session SPUDJ5 according to the invention. In other words, if such a valid token is not present in the session SPUD_S (answer no to step F30), the management method according to the invention is not implemented (step F40).

It is assumed here that the module 5A detects the presence of a valid token in the SPUD OPEN signaling message sent to step F20 (yes response to step F30). He deduces that the VIDEOJ5 transmission session is collaborative, in other words that the data associated with the video stream of this session will be managed and possibly prioritized according to the invention. This detection triggers the application of the steps of the management method according to the invention to the transmission session VIDEO_S-

More particularly, this triggers the obtaining by the first obtaining module 5B of information representative of transmission conditions of the video stream experienced by the terminal 2 on the network during the VIDEO_S session, and in particular on the access network. AN (step F50).

This information is obtained for example here via the technical solution MTG (Mobile Thoughput Guidance), standardized by the IETF and which allows a cellular network to report in almost real time information on the transmission conditions of the video stream. This information includes in particular here information sent by the base station 4 on the cell to which the terminal 2 is attached (eg cell identifier or "cell-id"), the location of the terminal 2, the load of the cell, and an indication of bit rate (or bandwidth) experienced by the terminal 2.

They are transmitted in the signaling conveyed by the transmission session VIDEO_S (see step E40 in FIG. 4).

Of course, if the access network is not a cellular network but for example a WIFI network, other known techniques can be envisaged to access this information.

The information obtained by the first obtaining module 5B is then analyzed by it to determine if the transmission conditions enjoyed by the VIDEO_S transmission session are favorable (test step F60). By "favorable" is meant here that the conditions experienced by the session are good enough to allow the terminal 2 to access the video stream without excessive latency. This is determined here by the first obtaining module 5B by comparing the load of the cell to which the terminal 2 is attached with respect to a predetermined threshold THR2. This threshold can be determined experimentally.

In a variant, if the access network AN is a WIFI network and not a cellular network, the obtaining module 5B compares the number of active connections on the WIFI access point considered with respect to a maximum number of connections.

Other parameters among the MTG information can be taken into account by the first obtaining module 5B to determine whether the transmission conditions are favorable or not, such as the speed experienced by the terminal 2, or the identifier of the cell, etc.

If the conditions are favorable (yes response to the test step F60), no treatment is applied by the management device 5 and the process is completed (step F40).

On the other hand, if the first obtaining module 5B determines that the conditions are not favorable (answer no to the test step F60), a timer TEMP is armed by the first obtaining module 5B for a predetermined duration T (step F70). This duration T is chosen to represent the start of the video transmission session. It can be chosen experimentally, based on feedback from content providers on user practices and their feedback (for example on what seems acceptable for a user like latency before accessing a video stream via its terminal, this being a predetermined criterion within the meaning of the invention). For example, this duration is chosen equal to T = 2s.

Then, the prioritization of the data relating to the video stream of the terminal 2 is triggered

(step F80), by activating the second obtaining module 5C and the selection module 5D.

More particularly, the second obtaining module 5C first obtains a current state STATE of the buffer 2C of the player 2B of the terminal 2 for the reproduction of the video stream (step F90). This current state is representative here of a filling level of the buffer 2C with data relating to the video stream. This state is obtained here by the second obtaining module 5C via a signaling message sent by the terminal 2 to the content server 3-1 in the signaling session SPUD_S (step E50 of FIG. 4), message to which the content server 3-1 responds via a SPUD ACK message (step E60 of FIG. 4). Since the session SPUD_S is a collaborative session transiting via the PoP 6, the management device 5, and in particular its second obtaining module 5C, can access the session SPUD_S, analyze it and obtain the current state of the buffer 2C used. by the terminal 2. It is assumed here that the terminal 2 is configured to periodically transmit the state of its buffer 2C in a signaling message on the session SPUD_S-

As a variant, other information in addition to the state of the buffer can be obtained by the second obtaining module 5B from the signaling messages exchanged in the signaling session SPUD_S, such as, for example, a type of terminal to which belongs the terminal 2, a type of service to which the terminal 2 accesses, etc.

Referring again to FIG. 3, the state STATE of the buffer 2C (filling level) of the player 2B of the terminal 2 is then compared by the obtaining module with the predetermined filling threshold THR1 (test step F100). This threshold is chosen preferentially so as to ensure that the data relating to the video stream stored in the buffer 2C of the player 2B of the terminal 2 are in sufficient quantity to start the viewing of the video stream by the user of the terminal. Note that by filling level is meant here either a relative value (eg a percentage of filling the buffer as soon as its size is known), or an absolute value (eg amount of data stored in the buffer or restitution time the available stream in the buffer expressed in seconds). The filling threshold THR1 depends, of course, on the capacity of the terminal 2 and the quality of the video received; it can, as an indication, vary from a few seconds (eg 20s) to several minutes.

If the second obtaining module 5B determines that the filling level of the buffer 2C is below the threshold THR1 and the timer TEMP is still armed (in other words, that the transmission session is still in a start-up period or that the duration T has not yet elapsed) (answer yes to the test step F100), the module 5D of selection selects a data prioritization policy for the video stream transmitted in the VIDEO_S session (step Fl 10).

If any of the above two conditions are not met (ie the STATE fill level is greater than the THR1 threshold and / or the TEMP timer has expired, ie the VIDEO_S transmission session is no longer in a start period) (answer no to the test step F100), the management method is completed (step F40).

In the embodiment described here, the selection module 5D selects as policy prioritization policy POLI which consists of removing the data relating to video streams of non-collaborative transmission sessions of terminals belonging to the same cell as the terminal 2.

The POLI prioritization policy selected by the selection module 5D is then notified by the management device 5 in a signaling message MESS (POLl) sent in the signaling session SPUD_S to an R router on the route between the terminal 2 and the content server 3-1 (step F120, steps E70 and E80 of FIG. 3). This message SPUD MESS (POLl) is for example an SPUD "advice" which requires the application of the POLI prioritization policy. More particularly here, it requires the deletion of the data relating to the video streams of the non-collaborative transmission sessions of the terminals belonging to the same cell as the terminal 2. This POLI policy is intended to be applied by at least one router R of the Internet network and / or the core network CN through which the video stream transmission sessions, and in particular the non-collaborative transmission sessions, pass.

In another embodiment, the selection module 5D selects as a prioritization policy a policy POL2 which consists in deleting the data relating to the video streams of the non-collaborative transmission sessions of the terminals belonging to the same cell as the terminal 2 and which present a latency greater than a predetermined latency threshold TH3. This policy POL2 is intended to be applied also by the routers of the Internet network and / or the CN core network through which the video stream transmission sessions, and in particular the non-collaborative transmission sessions, pass in a manner similar to POLI policy.

In yet another embodiment, the selection module 5D selects as policy prioritization policy POL3 which consists of adapting the speed of sending data to the terminal as a function of the filling level of the buffer of the terminal and the flow rate experienced by this one. This policy POL3 also includes here a redirection of the transmission session VIDEO_S to the streamer 7, so that the video stream for the terminal 2 passes through the streamer 7 (the streamer 7 is thus an intermediate device in the sense of the invention). This redirection of the transmission session VIDEO_S to the streamer 7 is implemented by the server 3-1, which thus applies the policy POL3 selected by the management device 5 and notified in the session SPUD_S between the terminal 2 and the server 3 -1. Alternatively, this redirection can be done by a router; in this case the POL3 policy is notified in the session SPUD_S between the terminal 2 and a router R, similarly to POLI or POL2 policies.

In the embodiment described here, following the redirection of the video stream intended for the terminal 2, the streamer 7 stores the data relating to the video stream (ie it acts as a cache) and in application of the POL3 policy, modulates the speed of the video stream. sending the data stored in the terminal 2 in order to reduce the latency experienced by the user of the terminal 2. More particularly, it modulates the speed of sending the data to the terminal 2 as a function here of the current level of filling of its buffer ( the streamer buffer 7) and the network throughput experienced by the terminal 2. This information is assumed here available in the MTG information reported in step F50.

The speed of sending the data is modulated here by the streamer 7 by organizing the data in the form of bursts which are sent to the terminal 2 during the start-up period T. Not to saturate the link between the streamer 7 and the terminal 2 , the size of the bursts is chosen so as to be consistent with the rate of the terminal 2 (ie the bandwidth it has). More precisely, the streamer 7 here chooses as burst size B, a function of the bandwidth available to the terminal 2, the size of the buffer of the streamer 7 and the average size of a packet of the video stream.

In yet another embodiment, the selection module 5D may select as a prioritization policy a combination of at least two policies selected from the POLI, POL2 and POL3 prioritization policies or other prioritization policies that may be contemplated. For example, the selection module 5D can select as the prioritization policy the combination formed of POLI policy (removal of video stream packets of non-collaborative sessions), and POL3 (redirection of the transmission session from terminal 2 to streamer 7 and modulation of the speed of sending the packets to the terminal 2 as a function of the bit rate available to the terminal 2).

Note that a single prioritization policy can be set by default at the 5D selection module or alternatively, several policies can be defined and one of them selected according to various factors such as network load access (load of the cell to which the terminal 2 is attached), the nature of the session, or several policies can be defined and prioritized and then selected according to the order thus established.

Following the application of the selected policy POLI by the selection module 5D, a monitoring is maintained by the management device 5 to detect whether the criteria conditioning the application of the prioritization of the data relating to the video stream of the terminal 2 are still respected (F130 test step). These criteria here include checking that the transmission session VIDEO_S is still in a start period (timer not expired) and that the filling level of the buffer is below the filling threshold THR1. They may also include checking that the conditions of transmission of the video stream experienced by the VIDEO_S session on the network are still unfavorable.

If any of these criteria is no longer met (answer no to the test step F130), the prioritization is interrupted (step F40).

If all the criteria are met (answer yes to the test step F130), the prioritization is maintained (step F140). In the embodiment described here, the selection module 5D then determines whether an update of the prioritization policy is necessary, for example as a function of the current state of the buffer and / or of the current transmission conditions of the video stream. experienced during the session on the network. The current information on the state of the buffer and on the conditions of transmission can be obtained via the signaling session SPUD_S and the MTG information reassembled periodically or in real time by the base station 4, as indicated previously (steps E90, E100 and E110 of Figure 4).

For example, if the current state of the buffer is always less than the filling threshold THR1 at the end of a predetermined period Tupd (of course less than the start period T), the selection module 5D can select a new Prioritization policy, such as, for example, the POL2 or POL3 policy or a combination of POLI, POL2 and / or POL3 policies in a pre-established order (step F140).

When the timer expires, the prioritization is interrupted (step F40). The management device 5 notifies this interruption in an SPUD MESS signaling message (STOP POLI) sent in the session SPUD_S (step E120 of FIG. 3). This message is for example a SPUD "advice" requiring the interruption of the application of the POLI policy (or of the current prioritization policy if it has been updated during step F140).

The invention thus proposes a technique (and an architecture supporting this technique) of prioritizing the data relating to a video stream transmitted to a terminal in a video session during the start-up period of the session in order to reduce the perceived latency. by the user of the terminal. Note that in the embodiment described here, to determine if the video session is in a start period, a duration T associated with that period has been considered and a timer has been armed for that period. Alternatively, the start period may be identified based on a quantity of data (eg, number of data packets) relating to the video stream transmitted by the content server and compared to a predetermined maximum amount.

Claims

A method of managing a transmission session (VIDEO_S) of a video stream between a content server (3-1) and a terminal (2) via a telecommunications network, said management method comprising, following a detection (F10) of a start of the session:

A step (F50) for obtaining information representative of transmission conditions of the video stream experienced during the session on the network;

- if said transmission conditions are not considered favorable (F60):

a step of obtaining (F90) a current state of a buffer used by a rendering module of the terminal for the reproduction of the video stream and representative of a filling level of the buffer; and

a step of selecting (F110) at least one prioritization policy to be applied to the transmission of the video stream to the terminal as long as the transmission session is in a start-up period with regard to a predetermined criterion and the buffer fill level is below a predetermined fill threshold.

2. Method according to claim 1 wherein said current state of the buffer is obtained from a signaling message sent by the terminal in a signaling session (SPUD_S) established with the content server in association with the transmission session of the video stream.

3. Method according to claim 2 wherein the signaling message and the signaling session are in accordance with the SPUD protocol.

4. The method of claim 2 or 3 wherein the detection (F10) of the start of the video transmission session comprises a detection of the establishment of the signaling session between the terminal and the content server.

5. Method according to any one of claims 2 to 4 further comprising a preliminary step (F20, F30) of determining whether the signaling session associated with the transmission session of the video stream is or not a so-called collaborative session, a policy prioritization method applied to the transmission of the video stream only if the signaling session is a collaborative session.

6. Method according to any one of claims 1 to 5 wherein the steps of obtaining a current state of the buffer and the step of selecting at least one prioritization policy are conditioned by the detection (F30) d a valid token in a signaling message sent by the terminal.

The method of any one of claims 1 to 6 wherein said at least one prioritization policy is selected from at least:

The method according to any one of claims 2 to 4 wherein the selected prioritization policy is notified (F120) in a signaling message sent in the signaling session established with the content server, said signaling message requesting the same. applying said at least one prioritization policy by at least one intermediate device between the content server and the terminal through which the video stream transits.

9. Method according to any one of claims 1 to 8 comprising a step of updating (F140) said at least one prioritization policy during the start period of the transmission session according to the current state of the buffer. and / or current transmission conditions of the video stream experienced during the session on the network.

The method of any one of claims 1 to 9 comprising:

During the application of said at least one selected prioritization policy, at least one step of obtaining (F130) information representative of transmission conditions of the video stream experienced during the session on the network; and

An interruption step (F40) of the application of said at least one selected prioritization policy if said transmission conditions are considered favorable.

The method of any one of claims 1 to 10 wherein the transmission session is in a start-up period if a period of time elapsed since the start of the transmission session is less than a predetermined maximum period or a quantity data relating to the video stream transmitted by the content server is less than a predetermined maximum quantity.

Computer program (PROG) comprising instructions for performing the steps of the management method according to any one of claims 1 to 11 when said program is executed by a computer.

A computer-readable recording medium on which a computer program is recorded including instructions for executing the steps of the management method according to any one of claims 1 to 11.

14. Device for managing (5) a transmission session (VIDEO_S) of a video stream between a content server and a terminal via a telecommunications network, said management device comprising:

A detection module (5A) for starting the session;

A first obtaining module (5B), activated on detection of a start of the session by the detection module and configured to obtain information representative of transmission conditions of the video stream experienced during the session on the network;

a second obtaining module (5C), configured to obtain a current state of a buffer used by a terminal rendering module for the reproduction of the video stream and representative of a level of filling of the buffer; and

a selection module (5D), configured to select at least one prioritization policy to be applied to the transmission of the video stream to the terminal as long as the transmission session is in a start-up period with regard to a predetermined criterion and that the filling level of the buffer is less than a predetermined filling threshold.

15. Management device (5) according to claim 14 characterized in that it is included in an access point (6) to the network.

16. Communication system (1) comprising:

At least one terminal (2);

At least one content server (3-1) capable of supplying a video stream to said terminal during a transmission session established with the terminal; and

A management device (5) for this transmission session according to claim 14; and at least one intermediate device (7, R) between the content server and the terminal through which the video stream transits and able to apply at least one prioritization policy selected by the management device if necessary for said transmission session. .