FR3079095A1 - REDUCTION OF THE TRIGGER AFFECTING A VIDEO STREAM DIFFUSE IN CONTINUOUS. - Google Patents

Abstract

A jitter reduction method for a streaming video data stream includes: - an identification (S3) of a streaming video data stream as belonging to a high service class jitter constraint; an activation of at least one prioritization mechanism of said identified video data stream; a configuration of a buffer depth within a rendering terminal (4) of said identified video data stream, said buffer memory being dedicated to the temporary storage of said stream before rendering by said terminal (4).

Description

Reduced jitter affecting a streamed video data stream.

1. Field of the invention

The field of the invention is that of the streaming of video data streams in continuous mode, also called in English “streaming”, i.e. the real-time transmission of video data over a network by packet stream. More specifically, the invention relates to the broadcasting of such video streams in a local communication network, for example a home network, when they are subjected to a strong latency constraint, or jitter.

2. Prior art and its drawbacks

In a data transmission network, the latency (or transit delay, or delay) corresponds to the data transmission delay, and designates the time necessary for a data packet to pass from the source to the destination across the network. The variation of this latency over time is called jitter, or in English "jitter".

This variation in latency can result from several alternative or cumulative phenomena, such as the level of priority granted to the different data streams received by an access point to a local network, possible disturbances or prioritizations linked to Wi- Fi® wireless radio transmission within this local network, or the temporary storage of data packets received before their return to the user.

In fact, in order to compensate for the harmful effects of jitter for the user, it is known to place a buffer memory (or in English "buffer") in the terminal for restoring the received data streams, in which a certain amount is stored. number of data packets, before the start of their delivery to the user. This jitter buffer therefore induces a detectable delay at the start of the restitution of the stream.

For a video broadcasting service (for example television signals), this slight shift in reproduction with respect to real time poses no problem for the user. However, it can be problematic for certain streaming services, such as, for example, video games.

Indeed, consider the case of a user who accesses a video game streaming service, from a game console connected via Wi-Fi® to a residential gateway constituting the access point to the user's local home network. . When the game console stores in temporary memory a large number of data packets associated with the video game, before their restitution to the user, the latter will experience a potentially annoying time difference between the moment when he launches an action via the joystick of his console (for example, the movement of a character), and the instant when the result of this action is actually displayed on the screen of his computer or television.

Such video streaming services therefore require a very short response time, and the lowest possible end-to-end jitter.

In order to achieve this reactivity objective, some video game consoles already offer to reduce the depth of the buffer memory in which the video streams are stored before playback. However, depending on the state of traffic between the source and the terminal for rendering the video stream, in particular within the user's local network, it sometimes happens that this buffer memory is completely emptied of the data packets it contains. , which leads to a phenomenon known as "starving", which results, on the user's screen, in a video that freezes.

There is therefore a need for a technique for streaming video data streams which does not have these drawbacks of the prior art. In particular, there is a need for such a technique, which makes it possible to reduce the jitter affecting such video data streams, while offering an adequate quality of reproduction for the user.

There is also a need for such a technique which is particularly well suited to the broadcasting mode of video game services, in particular in the context of a local home network, in which the terminal for rendering the video stream is connected by WiFi® to a residential gateway forming an access point to the local network.

3. Statement of the invention

The invention meets this need by proposing a method for reducing a jitter affecting a stream of video data broadcast, which comprises:

an identification of a streamed video data stream as belonging to a class of services with high jitter constraint;

an activation of at least one prioritization mechanism of said identified video data stream;

a configuration of a buffer memory depth within a terminal for restoring said identified video data stream, said buffer memory being dedicated to the temporary storage of said stream before restitution by said terminal.

Thus, the invention is based on a completely new and inventive approach to the broadcasting of video streams in “streaming” mode, in particular within a local network of the home network type. Indeed, it is based on a process, implemented in the local network access point, for example the user's residential gateway, which makes it possible to act jointly on two important levers, namely, on the one hand a configuration of the depth of the buffer of the playback terminal, the configuration consisting in reducing or increasing the depth of the buffer memory; and secondly, improve the quality of service (QoS) associated with the flow, by activating one or more prioritization mechanisms, at the residential gateway level.

Note that configuring a buffer depth of a rendering terminal consists of defining a buffer size to be used for a given stream. The actuation of these two main levers is done after the video stream streamed has first been identified as having a strong jitter constraint, as opposed to conventional video streams, such as video streams broadcast live (live ), streams from online video recorder (nPVR for “Network Personal Video Recorder”), video on demand (VOD for “Video On Demand”), delayed streamed video streams (replay), etc. This is particularly the case for video streams corresponding to video game services, accessible from a game console or game services in Cloud mode (in French, cloud) from a television set-top box (in English "set-top" box ”).

According to a first aspect, the configuration of the buffer memory depth comprises a reduction in the buffer memory depth, compared to a buffer memory depth conventionally used for broadcasting a video stream of the deferred type, or VOD.

According to one aspect, the identification of a video data stream as belonging to a class of services with high jitter constraint results from access by the terminal for rendering the video data stream to a control interface by which it declares the video data stream as belonging to a class of services with strong jitter constraints. Thus, a control API ("Application Programming Interface") is installed on the residential gateway. The playback terminal, for example the game console, can access it to indicate that the video streams it receives are very time-constrained, and must be prioritized by the residential gateway.

According to another aspect, this identification results from a determination of an address of a source of the stream of video data broadcast continuously. Thus, based for example on the URL (in English "Uniform Resource Locator") on which we just read the video stream, the residential gateway identifies that it is a stream to be prioritized, because with high constraint of jitter. One can indeed imagine that the gateway has at its disposal a list of URLs, corresponding to providers of “streamed” video games (streamed), who would have declared themselves beforehand with the access provider as broadcasting content with strong jitter constraints.

According to one aspect of the invention, the configuration of a buffer memory depth comprises a transmission to the terminal for rendering the buffer memory depth, determined as a function of a transmission rate of the identified video data stream, and of a maximum latency period allowed.

Thus, the residential gateway determines the optimal depth of the buffer of the playback terminal (for example a computer, a tablet or a game console), as a function of the transmission rate of the video data stream within the home network, and a maximum latency period allowed. This maximum latency period, between the action of a user on a joystick for example, and the visualization of this action on a screen for restitution of the flow, must generally not exceed 25 ms, for adequate playing comfort of the user.

According to a first aspect of the prioritization, the prioritization mechanism implements a bandwidth reservation dedicated to the identified video data stream, on a wireless radio transmission channel to the playback terminal. Thus, the residential gateway reserves Wi-Fi® bandwidth in the home network for “streamed” video games.

According to another aspect of the prioritization, the prioritization mechanism implements a prioritization of the data flow at the level of an IP / TCP layer (“Internet Protocol / Transmission Control Protocol”) by marking a ToS / DSCP field ( "Type of Service / Differentiated Services Code Point") of a data packet header for the stream.

According to another aspect of the prioritization, the prioritization mechanism implements a reservation of a time space dedicated to the identified video data stream, on a wireless radio transmission channel to the playback terminal.

According to yet another aspect of prioritization, the prioritization mechanism implements an association of the identified data stream with a high-priority access category of wireless radio transmission.

These different prioritization mechanisms can be combined, or selected independently, by the residential gateway, to ensure broadcasting of the video stream guaranteeing the continuous playback of the video by the playback terminal with a minimum buffer depth.

According to another aspect, such a method also comprises a temporary assignment of a reduced priority level to at least one data stream which is not identified as belonging to a class of services with high jitter constraint. In fact, in order to prioritize this video stream identified as having a high time constraint, the residential gateway can, in return, temporarily increase the latency of other video services, such as video on demand or delayed broadcasting.

According to yet another aspect, such a method comprises at least an update of the configuration of the depth of the buffer memory, as a function of a change in the transmission rate of the identified video stream. Thus, the gateway can detect an increase or a decrease in the flow in the local network, or at the entry in the access point, and consequently ask the restitution terminal to dynamically adjust the depth of its buffer, to maintain a quality of video playback satisfactory for the user.

The invention also relates to a computer program product comprising program code instructions for implementing a method as described above, when executed by a processor.

The invention also relates to a recording medium readable by a computer on which a computer program is recorded comprising program code instructions for the execution of the steps of the jitter reduction method according to the invention as described below. -above.

Such a recording medium can be any entity or device capable of storing the program. For example, the support may include a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or else a magnetic recording means, for example a USB key or a hard disk.

On the other hand, such a recording medium can be a transmissible medium such as an electrical or optical signal, which can be routed via an electrical or optical cable, by radio or by other means, so that the program of computer it contains is executable remotely. The program according to the invention can in particular be downloaded from a network, for example the Internet.

Alternatively, the recording medium can 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 aforementioned display control method.

The invention also relates to a residential gateway and a terminal for restoring a stream of video data broadcast continuously having all or part of the characteristics described throughout this document.

In particular, the residential gateway (HGW) comprises a processor capable of implementing the steps of the jitter reduction method as described above.

The terminal for reproducing a stream of video data streamed comprises means for accessing a control interface of a residential gateway and means for declaring the video data stream as belonging to a class of highly constrained services jitter; it also includes means for configuring a depth of buffer memory, this buffer memory being dedicated to the temporary storage of the stream before restitution by the terminal.

According to one aspect of the invention, such a restitution terminal comprises means for observing a filling rate of the buffer memory, and means for transmitting, to the residential gateway, a request for modification of the prioritization activated, depending on the filling rate observed.

The aforementioned residential gateway, terminal and computer program have at least the same advantages as those conferred by the jitter reduction method according to the present invention.

4. List of figures

Other objects, characteristics and advantages of the invention will appear more clearly on reading the following description, given by way of simple illustrative example, and not limiting, in relation to the figures, among which:

FIG. 1 presents a block diagram of the jitter reduction method, in a local home network, according to an embodiment of the invention;

Figure 2 is an illustrative diagram of the hardware structure of a residential gateway of the home local area network of Figure 1;

FIG. 3 illustrates the hardware structure of a terminal for rendering a video stream in continuous mode of the domestic local area network of FIG. 1.

5. Detailed description of embodiments of the invention

The general principle of the invention is based on a dual mechanism for prioritizing a video stream broadcast continuously, at a gateway to a local network, and for configuring the depth of the buffer memory of a playback terminal of this stream, in order to allow the video stream to be played continuously without blocking at the level of the playback terminal, and thus improve the user experience.

The dynamic activation of such techniques for prioritizing video streams makes it possible to both reduce and stabilize the latency time (preferably below 25 ms for video game streams). In addition, it limits jitter, i.e. fluctuations in latency, which is thus reduced to a minimum of variations, and allows excellent playing comfort for "streamed" video games (i.e. streamed).

By way of illustrative example, we now present, in relation to FIG. 1, the general principle of this mechanism in a local home network (LAN for "Local Area Network") referenced 6. A residential gateway HGW 1 (HGW for l 'Home Gateway') is the access point to this local LAN 6 network, from the WAN (for Wide Area Network) communication network. Various pieces of equipment are connected to the local network 6, for example a personal computer PC 2, a video decoder, or set-top box STB 3, a game console PS 4, and a TV set 5. As symbolized schematically in FIG. 1, the link between the HGW 1 residential gateway and the PC 2 computer is of a wired nature (RJ45 cable for example), while the PS 4 game console and the STB 3 decoder are connected to the HGW 1 residential gateway by a radio link Wi-Fi® type wireless. This is of course only an illustrative example, and one could imagine for example that all the equipment of the local network 6 are connected by Wi-Fi® to the residential gateway HGW 1.

As symbolized by the dotted arrow SI, video content is broadcast from the wide area network WAN on the STB 3 decoder, through the residential gateway HGW 1. This video content is for example of VOD (video on demand) type, or television content, live (live) or delayed (replay). This video stream therefore does not have a strong jitter constraint, and can be broadcast in a conventional manner, according to the techniques of the prior art. The buffer depth (most often expressed in kilobytes or KB), or buffer memory, on the STB 3 decoder, can therefore be significant, so as to guarantee the continuous playback of video streaming, without the appearance of "starving" phenomenon. », Even in the event of major network disturbances. After decoding by the STB 3 decoder, the video stream can be viewed on the TV set 5. It will be noted that, for the sake of simplification, the connection between the STB 3 decoder and the TV set 5 has not been shown in the figure. 1, although it exists.

In parallel, or at the end of this broadcast, a user decides to launch a video game, which is "streamed" on the PS 4 game console, as symbolized by the dotted arrow S2, from the WAN wide area network, through of the HGW 1 residential gateway. As a variant, this video game could also be broadcast, not on the PS 4 game console, but on the STB 3 decoder, for example from the URL of a provider of video games broadcast in continuous, of the Gcluster® type.

This video game service is subject to strong jitter constraints, in the sense that it requires very low jitter, for optimal user enjoyment of the game.

As symbolized by the dotted arrow S3, the game console PS 4 then accesses the control API present on the residential gateway HGW 1, in order to initialize the mechanism intended to control the jitter of the video stream, which is thus set up works dynamically at the launch of the game. This control API, exposed by the residential gateway HGW 1, is accessible to all the equipment on the local LAN 6 network (STB 3 decoder, PS 4 game console, connected TV, computer PC 2, ...). This API allows you to select the class of service to use for the video stream.

The PS 4 game console therefore accesses the API of the HGW 1 residential gateway, which allows it to identify the video stream to be received as belonging to a class of service with strong jitter constraints. The PS4 game console then configures a very small buffer depth, either on its own initiative or on receipt of a command message from the HGW 1 residential gateway. The depth of this buffer memory can be calculated by the residential gateway, based on the transmission rate measured for the video stream streamed on the PS 4 game console, and a maximum latency time authorized for this class of service.

This depth of “buffer” can be provided by the residential gateway HGW 1 to the game console PS 4 during the call to the control API, and also on a regular basis, depending on the evolution of network conditions.

The video stream required by the PS 4 game console being identified as belonging to a class of service with strong jitter constraints, the residential gateway then configures for this stream different prioritization parameters, which will make it possible to ensure a broadcast of the stream guaranteeing streaming of the video by the game console, despite the minimal buffering.

Among these prioritization parameters, the HGW 1 residential gateway can act on network scheduling (in French "scheduling"), traffic prioritization using the ToS field ("Type of Service"), the type of Wi-Fi service Fi® or even Wi-Fi® bandwidth reservation.

Indeed, the HGW 1 residential gateway can use many different mechanisms to dynamically manage the prioritization of a temporary session of a game broadcast continuously. To begin with, the video stream associated with this game can be identified by marking at the IP / TCP layer, using the ToS / DSCP ("Type of Service / Differentiated Services Code Point") field. This ToS / DSCP field, in the header of the transmitted data packets, defines the class of service of the stream to which the packets belong. It is thus possible to prioritize the flow at the level of the IP router, with a different scheduling. Indeed, the “Type of Service” (TOS) field in the IPv4 header has had several functions during the evolution of IP standardization, but is currently used in two parts; 6 bits are used for the “Differentiated Services Code Point” (DSCP) field and 2 bits for the “Explicit Congestion Notification” field.

The value of the six bits of the DSCP field of the IP header determines the management of traffic priorities, called "per-hop behavior" (PHB), by the routers in the domain. This priority management (PHB) is carried out according to the different types of flows (Voice over IP VoIP, multimedia, etc.). By default, the PHB has minimum priority (“b est-effort delivery”, bits of value 000000), and can go up to real-time. Thus, the use of this DSCP field specifies a mechanism to classify and control traffic while providing quality of service (QoS), differentiating services from data.

To prioritize the flow, the residential gateway HGW 1 can also use the access categories (ACs for “access categories”), ie the priority levels of the access method to the EDCA channel (“Enhanced Distributed Channel Access” for “ improved distributed channel access ”) defined in the IEEE 802.11e standard. The latter defines quality of service (QoS) mechanisms, mainly at the level of the MAC layer (Data link layer of the OSI model) of the standard, in 802.11 networks, i.e. digital local wireless link networks.

With the EDCA method, high priority traffic has a higher probability of being sent than low priority traffic: a terminal with high priority traffic waits a little less time before sending its packets, medium, compared to a terminal with low priority traffic.

The ACs access categories defined in this EDCA method define the priority levels associated with the service classes below

Priority Priority 802.IP> Designation 802.IP

Most 1 ¹ | BK - Background low I 2 -Spare 0 BE - Best Effort 3 EE - Excellent Effort : 4 CL - Controlled Load 5 VI - Video 6 VO - Voice Most : 7 NC - Network high Control

Access category (Access Category (AC)) WMM designation (Wi- 1 1 f Fi® Multimedia) j 1 1 1 1 AC_BK 1 day I i he i background AC_BE l 1 | Best Effort | 1 1 1 I AC_VI r ¹ ................................................ .................................................. .................................................. ...................................... i [Video j 1 1 AC_VO Voice j 1 1 1 1 1 1

TABLE 1

It is thus possible to switch to very high prioritization on Wi-Fi®, by configuring, at the level of the residential gateway HGW 1, the video stream to be streamed continuously on the game console PS 4, with the highest priority, at know AC_VO.

Another possible prioritization setting for the video stream consists, for the HGW 1 residential gateway, of forcing a reservation of a specific time slot on the Wi-Fi® channel which connects it to the PS game console. 4, by the “Add Traffic Stream” (ADDTS TSPEC (Traffic Specification)) mechanism of the IEEE 802.11 standard.

Other prioritization mechanisms, making it possible to activate the jitter reduction method specifically towards a terminal of the local network having initiated it by identification of a high priority video stream, can also be implemented.

For example, it is possible to create a BSSID service identifier dedicated to the reduction of jitter. As a reminder, BSS (for "Basic Service Set") designates all of the wireless terminals which can communicate with each other at the PHY layer. Each BSS set has an identifier (ID), called BSSID, which is the MAC address of the access point serving that BSS set. Thus, the residential gateway HGW 1 can cause a disconnection of the MAC from the PS 4 game console, in order to reconnect it rather in P2P mode (“Peer-to-Peer”, ie Wi-Fi® direct) on another BSSID Wi -Fi® associated with the same ESSID (“Extended Service Set ID”, where an ESS is a set of connected BSS) and with the same security parameters.

The jitter reduction method according to an embodiment of the invention therefore consists, at the access point or the residential gateway HGW 1, in voluntarily and temporarily "breaking" the static QoS configuration, at the risk of degrading the other services during this anti-jitter session. Thus, the other Wi-Fi® stations of the local LAN 6 network (for example the STB 3 decoder or the PC 2 computer) may be subject to the temporary impact of the prioritization of the video game flow to the PS 4 game console, on the prioritization of their flow, the priority level of which may be temporarily lowered.

We now present, in relation to FIG. 2, the hardware structure of a residential gateway HGW 1 according to an embodiment of the invention, in which the gateway incorporates a unit for reducing jitter affecting a video stream broadcast continuously , within the local network to which the gateway forms an access point.

The term unit can correspond as well to a software component as to a hardware component or a set of hardware and software components, a software component corresponding itself to one or more computer programs or subroutines or more generally to any element of a program capable of implementing a function or a set of functions.

More generally, such a residential gateway HGW comprises a random access memory 23 (for example a RAM memory), a processing unit 22 equipped for example with a processor, and controlled by a computer program, representative of the reduction unit of the jitter, stored in a read only memory 21 (for example a ROM memory or a hard disk). On initialization, the code instructions of the computer program are for example loaded into the RAM 23 before being executed by the processor of the processing unit 22. The RAM 23 contains in particular the assigned prioritization parameters to the different data flows in transit through the residential gateway to the local LAN 6 network, as well as the classes of service associated with these different flows, and the buffer depth calculated for the terminals for rendering these priority flows. The processor of the processing unit 22 controls the various mechanisms for prioritizing the flows described above, the transmission to the playback terminals of the local network of the depth of the buffer memory to be configured, as well as the control API accessible to the user. '' all the LAN 6 network terminals (STB 3 decoder, PC 2 computer, PS 4 game console, connected TV, etc.).

FIG. 2 illustrates only one particular way, among several possible, of producing the residential gateway HGW, so that it performs the steps of the detailed process above, in relation to FIG. 1. In fact, these steps can be carried out indifferently on a reprogrammable calculation machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated calculation machine (for example a set of logic gates such as an FPGA or an ASIC, or any other hardware module) .22

In the case where the HGW residential gateway is made with a reprogrammable computing machine, the corresponding program (i.e. the sequence of instructions) can be stored in a removable storage medium (such as for example a floppy disk , CDROM or DVD-ROM) or not, this storage medium being partially or totally readable by a computer or a processor.

The different embodiments have been described above in relation to a residential gateway of the Livebox® type, but can more generally be implemented in all gateways or routers ...

We now present, in relation to FIG. 3, the hardware structure of a terminal for rendering a streaming video stream according to an embodiment of the invention, for example the game console PS 4 of FIG. 1 Such a terminal notably comprises a control unit for the depth of a buffer memory, in which the packets of the video data stream are temporarily stored before their restitution to the user.

The term unit can correspond as well to a software component as to a hardware component or a set of hardware and software components, a software component corresponding itself to one or more computer programs or subroutines or more generally to any element of a program capable of implementing a function or a set of functions.

The rendering terminal 30 of FIG. 3 comprises a processor 31, a storage unit 32, an input device 33, an output device 34 and an interface unit 34, which are connected to each other by a bus 36. Of course, the components of the rendering terminal 30 can be connected to each other by any other type of connection, instead of the bus 36. Such a rendering terminal 30 is for example a PS 4 game console , or an STB 3 decoder, or a PC 2 computer.

The processor 31 controls the operation of the rendering terminal 30. The storage unit 32 stores at least one computer program, intended to be executed by the processor 31, and various data, including the reduced depth of buffer memory transmitted by the residential gateway HGW 1, as well as various parameters necessary for the operations carried out by the processor 31. The storage unit 32 can in particular contain the buffer memory, the depth of which is configurable according to an embodiment of the invention, and which is intended to store temporarily packets of the video data stream received from the residential gateway HGW 1, before their restitution to the user.

The processor 31 can be produced in hardware, software form, or in the form of a hardware and software combination. For example, the processor 31 can be designed in the form of a dedicated hardware component, such as an integrated circuit, or of a programmable processing unit of the CPU type ("Central Processing Unit" for central processing unit) which runs a computer program stored in memory.

The storage unit 32 can take any form suitable for storing a program or computer-readable data, for example a computer-readable storage means such as a semiconductor memory, or a magnetic recording means. , optical or magneto-optical loaded in a read / write accessible unit.

The program causes the processor 21 to execute various actions, including:

access to the HGW 1 residential gateway control API, to identify the video data stream to be streamed as belonging to a class of service with high jitter constraints;

the configuration of the depth of the buffer memory contained in the storage unit 82, according to the instructions received from the residential gateway HGW 1;

monitoring the filling rate of this buffer memory, and transmitting, if necessary, to the residential gateway HGW 1, a request to modify the activated prioritization mechanism, as a function of the filling rate observed.

The input device 33 can take the form of a keyboard, a game controller, a mouse, or any other form allowing a user to enter commands or actions relating to the streaming video stream. . The output device 34 can take the form of a screen for viewing the restored video stream, or a screen for controlling the commands entered by the user.

The interface unit 35 provides an interface between the rendering terminal 30 and an external device, such as the residential gateway HGW 1 or the television 5 for example. The interface unit 35 can be wired or wireless with the external device (for example, in Wi-Fi® connection with the residential gateway HGW 1, but in cable connection with the television set TV 5). In an exemplary embodiment, the playback terminal can be the PS 4 game console. In this case, data packets of the video stream streamed can be received by the playback terminal 30, coming from the residential gateway HGW 1, through the interface unit 35, then stored in the buffer memory of the storage unit 32, before being restored, for example on the screen of the television set TV 5.

Although a single processor 31 has been shown in FIG. 3, this processor can include different modules and units, implementing the functions of the rendering terminal 30, according to the embodiments of the present patent application, such as:

an access unit to the control API of the residential gateway HGW 1, to identify the class of service of the video stream received, at the launch of the video game;

a buffer depth configuration module;

a unit for observing the filling rate of this buffer memory, and for transmitting a request to adapt the priority associated with the stream, as a function of the filling rate observed;

a unit for decoding the video stream before restitution;

a transmission module, in the network, of commands received from the user, for example via a joystick.

These different modules and units can also be embedded in several processors 31 communicating and cooperating with each other.

FIG. 3 illustrates only one particular way, among several possible, of producing the rendering terminal 30, so that it performs the steps of the method detailed above, in relation to FIG. 1. In fact, these steps can be carried out indifferently on a reprogrammable computing machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of logic gates such as an FPGA or an ASIC , or any other hardware module).

In the case where the rendering terminal 30 is produced with a reprogrammable calculation machine, the corresponding program (that is to say the sequence of instructions) may be stored in a removable storage medium (such as for example a diskette, CDROM or DVD-ROM) or not, this storage medium being partially or totally readable by a computer or a processor.

Claims (16)

1. Method for reducing a jitter affecting a stream of video data broadcast continuously, characterized in that it comprises: an identification (S3) of a streamed video data stream belonging to a class of services with high jitter constraints; an activation of at least one prioritization mechanism of said identified video data stream; a configuration of a buffer memory depth within a terminal (4; 30) for restoring said identified video data stream, said buffer memory being dedicated to the temporary storage of said stream before restitution by said terminal (4; 30). 2. A jitter reduction method according to claim 1, characterized in that said configuration of a buffer depth comprises a reduction of said buffer depth. 3. A jitter reduction method according to any one of claims 1 and 2, characterized in that said identification results from access of said reproduction terminal (4; 30) of said video data stream to a control interface by which it declares said video data stream as belonging to a class of services with strong jitter constraints. 4. A method of reducing jitter according to any one of claims 1 and 2, characterized in that said identification results from a determination of an address of a source of said stream of video data streamed. 5. A jitter reduction method according to any one of claims 1 to 4, characterized in that said configuration comprises a transmission to said terminal for restoring said depth of buffer memory, determined as a function of a transmission rate of said stream of identified video data, and a maximum latency period allowed. 6. Jitter reduction method according to any one of claims 1 to 5, characterized in that said prioritization mechanism implements a bandwidth reservation dedicated to said identified video data stream, on a wireless radio transmission channel to said rendering terminal. 7. A jitter reduction method according to any one of claims 1 to 6, characterized in that said prioritization mechanism implements prioritization of said data flow at an IP / TCP layer ("Internet Protocol / Transmission" Control Protocol ”) by marking a ToS / DSCP (“ Type of Service / Differentiated Services Code Point ”) field of a data packet header of said stream. 8. Jitter reduction method according to any one of claims 1 to 7, characterized in that said prioritization mechanism implements a reservation of a time space dedicated to said identified video data stream, on a radio transmission channel wirelessly to said rendering terminal. 9. Jitter reduction method according to any one of claims 1 to 8, characterized in that said prioritization mechanism implements an association of said identified data stream with a high priority access category of wireless radio transmission . 10. A method of reducing jitter according to any one of claims 1 to 9, characterized in that it also comprises a temporary assignment of a reduced priority level to at least one data stream which is not identified as belonging to a class of services with strong jitter constraints. 11. A jitter reduction method according to any one of claims 1 to 10, characterized in that it comprises at least one update of said configuration, as a function of an evolution of said transmission rate of said identified video stream. 12. Computer program product comprising program code instructions for implementing a method according to any one of claims 1 to 11, when executed by a processor. 13. A computer-readable recording medium on which a computer program is recorded comprising program code instructions for executing the steps of the method according to any one of claims 1 to 11. 14. Residential gateway (HGW 1), characterized in that it comprises a processor (21) capable of implementing the steps of the jitter reduction method according to any one of claims 1 to 11. 15. Terminal (30) for rendering a stream of video data broadcast continuously, characterized in that it comprises means of access to a control interface of a residential gateway (HGW 1) and means of declaration of said video data stream as belonging to a class of services with high jitter constraint and in that it also comprises means for configuring a depth of buffer memory, said buffer memory being dedicated to the temporary storage of said stream before restitution by said terminal. 16. Restitution terminal according to claim 15, characterized in that it comprises means for observing a filling rate of said buffer memory, and means for transmitting, to said residential gateway, a modification request. said activated prioritization mechanism, as a function of said observed filling rate.