FR2865598A1 - Multimedia e.g. video, sequence transmitting system for use over Internet, has management server including information processing unit to process access query for multimedia sequences and control activity levels of servers over network - Google Patents

Abstract

The system has a management server (8) including an information processing unit for processing an access query for multimedia sequences. The processing unit analyzes and controls the query for the multimedia sequences, and controls activity levels of servers (3) connected over a network (7). The processing unit selects one server according to the query, and controls multimedia sequential transmission from the servers towards a receiver.

Description

SYSTEM FOR DIGITAL TRANSMISSION OF MULTIMEDIA SEQUENCES VIA ONE

  INTERNET TYPE COMMUNICATION NETWORK

  Introduction to audio and video streaming. State of the art Explanation of some of the abbreviations used: RTSP: real time streaming protocol HTTP: hypertext transfer protocol IRE: internet key exchange SSL: secure socket layer TLS: layer security transport IP: ATM protocol: asynchronous transfer mode ISDN The term streaming refers to the set of techniques intended to transmit multimedia sequences (audio, video and possibly other) in digital form from a transmitter to a receiver, the receiver starting to process the transmission. sequence before receiving it completely.

  Typically, an installation comprises streamers, or stream servers, or servers, which transmit audio or video streams from a local hard disk, a satellite dish, a terrestrial digital television receiver, a camera, or any other means to dedicated receivers called set-top boxes or micro computers. In the following description, these receivers (set-top boxes or micro computers) will be called customers. Such an installation is frequently accompanied by a website allowing users to access the various multimedia contents from their set-top box or microcomputer in a simple and user-friendly manner. From a practical point of view, this site most often contains links to the different streamers, with which the clients interact directly, using the standard Real Time Streaming Protocol (RTSP) to access the different streams.

  The invention relates to a system for digital transmission of multimedia sequences via a communication network, in particular of the Internet or ASM type. The system comprises: - servers connected to transmitters, in particular of the hard disk type, satellite antenna, video camera, cable, - receivers, in particular of the type dedicated receivers or computer equipment connected to TV-type viewing screens.

  The servers and receivers are connected to the communication network of the Internet type. The system is characterized in that it comprises a manager server connected to the servers. The management server includes computer processing means for: interpreting and processing requests for access to the RTSP type multimedia sequences, analyzing and controlling access requests to the RTSP type multimedia sequences originating from the receivers; monitor server activity levels in real time, - select at least one server among the servers 35 according to the requests and activity levels of the servers, - order the servers thus selected to broadcast the multimedia sequences to the receivers, via the communication network of the Internet type.

  Thus, the management server provides control and continuity of the broadcast of the multimedia sequences.

  The management server further comprises computer encryption means for encrypting multimedia sequences and queries using protocols, including IPsec, SSL and TLS. The computer encryption means are intended to: - ensure the confidentiality and integrity of the reception of requests and the broadcasting of multimedia sequences, - accelerate the transition times between multimedia sequences issued by different servers. The manager The streaming solution according to the invention has a difference compared to this conventional approach: a system controlling all the streamers, known as the manager, is an integral part of the solution. Instead of interacting directly with the streamers, the clients only address this unique manager (also using the standard RTSP protocol), and it is the manager who in turn controls the streamers by using a simpler protocol for multimedia streams to be sent to the clients who request them.

  The manager is a software that fulfills both the Real Time Streaming Protocol (RTSP) server function and the HTTP server function. The difference compared to the traditional approach is twofold: on the one hand, this software is the only one to fulfill both the functions of RTSP server and HTTP server, on the other hand, the manager is not satisfied with orient the client to the right streamer, but dialogue with him and pilot the streamer according to the client's instructions. At no time does the client give orders to the streamer without going through the manager.

  FIG. 1 represents the conventional architecture of a transmission of multimedia sequences according to the prior art: a request 1 is sent from a receiver 2 to streamers 3 connected to transmitters of satellite antenna type 4a, digital terrestrial television 4b or cable 4c. In response to the request 1, the streamers 3 transmit back to the receiver 2 a stream of multimedia sequences 5, via a computer network 7, intended to be broadcast on a display screen 6.

  FIG. 2 represents the architecture of a transmission of multimedia sequences according to the invention: a request 1 is sent from a receiver 2 to a manager manager server 8. The manager manager server 8 addresses control instructions 9 to streamers 3 connected to transmitters of satellite antenna type 4a, digital terrestrial television 4b or 4c cable. The streamers 3, according to the control instructions 9, transmit to the receiver 2 a stream of multimedia sequences 5, via a computer network 7, intended to be broadcast on a display screen 6.

  Advantages of this approach A first advantage of this mode of operation is that the manager is a central point of passage for all requests for access to content. Thus, it is easy to set up a system of billing, statistics, and access control (that is to say, to edit individual invoices for each client, calculated according to the media they accessed and decide whether or not to grant access to certain resources to a customer, based, for example, on their subscription plan).

  In addition, the manager is able to know at any time the status of the different streamers, and can therefore support load balancing and high availability operations. In other words, it is able to ensure continuity of service in case of failure or overload of one of the streamers, a much more difficult operation to perform and much less reliable in the case of autonomous streamers.

  Finally, the integration of an HTTP server to the manager ensures its ability to exchange more information than allowed by the RTSP protocol alone, so the website often accompanying video streaming solutions can be integrated into the manager and then has access to all its internal variables, which makes it easy and inexpensive to develop a site presenting the end user with a view of all the operations that he / she performs or can perform. For example, personal playlists can very easily take place on the manager, even if they use streams distributed on different streamers.

  Finally, the solution as a whole is controlled by the network administrator by handling only the manager, which significantly reduces the cost of administration and troubleshooting time.

  Content Protection One of the most common problems when deploying streaming solutions is controlling access to broadcast streams. Streams are sent over a computer network in unicast (that is, to a single client) and / or in multicast (in which case any client making the request receives the stream, while the server does not transmit the stream only once). In the case of unicast, however, there are methods that can allow a malicious client to receive the flow for another client. In the case of unicast, a client has almost nothing to do to get the flow. It is therefore useful to encrypt the stream, and not to communicate the key needed to decrypt it to its legitimate recipients.

  Case of the IP Network This part deals with the content protection solution according to the invention intended for networks where the IP protocol can be deployed. This consists in encrypting the flows that are not intended for all by relying on the IPsec standard, which is part of the IP protocol. This standard is well known and can encrypt any IP packet. However, it is not within the purview of IPsec to specify how the participants in a communication exchange their encryption keys. A complementary IPsec protocol, IKE (Internet Key Exchange), allows this exchange, but only in the case of unicast streams (while it is not for this type of flow that the security problem is the most important ). In addition, its implementation is delicate.

  The solution according to the invention is based on the association of IPsec and two other protocols, also well known SSL and TLS. These two protocols make it possible to encapsulate the communication between the clients (set-top boxes or microcomputers) and the RTSP server (thus the manager) in an encrypted communication. Thus, the confidentiality of the dialogue between the customer and the manager is ensured. The RTSP protocol is therefore slightly extended, so as to allow the manager to provide customers who need the keys to decrypt the streams to which they have legitimate access. These keys are generated randomly by the streamers, and the manager can query the streamers to know them when he has to communicate them to the customers. This allows to change regularly key.

  Thus, a classic approach to encrypted streaming over IP networks would be that customers, when they connect to each streamer (the conventional approach does not include a manager), issue their RTSP requests, exchange the necessary keys with the streamer at the same time. help from IKE, and receive encrypted streams in IPsec and decrypt them. This approach has two disadvantages: the keys can not be exchanged in this way for the multicast streams, and the IKE key exchange process is quite long, the transition from one channel to another, if the two chains do not are not issued by the same streamer, takes a lot of time.

  The solution according to the invention based on a single manager, this latency problem is eliminated. In addition, since key exchange does not take place in IKE but in RTSP extended and encapsulated in SSL or TLS, multicast streams can also be protected using IPsec and deciphered by their legitimate receivers.

  In addition, the use of IPsec not only ensures the confidentiality of the streams (only authorized users can read the data), but also their integrity (the stream was not corrupted on the way due to an error or to a malicious act).

  Case of non-IP networks On networks that can not accommodate the IP protocol, or networks whose operators do not wish to deploy this protocol, the principle of the key exchange solution remains applicable as it is. Thus, encryption keys can be exchanged using the extended RTSP protocol and encapsulated in SSL or TLS, regardless of the type of underlying network. However, the IPsec standard can not be used on such networks, so the encryption performed using the keys exchanged in this way will be encapsulated in another protocol, depending on the underlying network, or possibly a non-standard protocol. The tricky part of this method of content protection is the exchange of keys.

  Move, Quick View and / or Reverse Move is the feature that allows a customer to request a streamer (or manager) to emit a stream from a specific position, such as playing a movie from the Twelfth minute.

  As for the quick view and the reverse view, they correspond to the forward and reverse functions of traditional analog video recorders.

  Displacement An important concept to take into account when dealing with moving by a streamer is that of image group. In a compressed digital video stream, the images are grouped into logical sequences, starting with a stand-alone image, which can be decoded and displayed without additional data, while the other images in the group are calculated based on this reference image.

  The implementation of the displacement in the solution according to the invention takes this feature into account, any displacement request is therefore approximated and results in a displacement towards the autonomous image closest to the target of the displacement.

  Thus, a displacement is realized more quickly from the point of view of the client, insofar as he can begin his decoding work as soon as he receives the data sent as a result of the displacement.

  Fast and Inverse Visualization These two visualization modes are realized by making displacements at the end of the emission of each group of images, respecting the principle according to which the emission as a result of a displacement always starts with an image autonomous. These movements take place in front or behind, and are more or less long depending on the speed of reading. A direct consequence is that only a portion of the image groups are sent to the client, the intermediate image blocks being completely ignored. This technique corresponds to the method specified by RFC 2326 governing the RTSP protocol.

  Conclusion The invention therefore makes it possible to set up a modular RTSP server capable of driving different streamers, and including an http server. The invention further allows content protection. The invention also provides a method of displacement and rapid visualization using the RTSP protocol.

Claims (1)

  1. System for digital transmission of multimedia sequences via a communication network (7), in particular of the Internet or ASM type; said system comprising: servers (3) connected to transmitters (4a, 4b, 4c), in particular of the hard disk type, satellite antenna, video camera, cable, receivers (2), in particular of the type dedicated receivers or equipment computer connected to viewing screens (6) of the television type; said servers (3) and said receivers (2) being connected to said communication network (7), in particular of the Internet or ASM type; said system being characterized in that it comprises a manager server (8) connected to said servers (3); said management server (8) comprising computer processing means for: interpreting and processing requests for access to said RTSP multimedia sequences (1), analyzing and controlling said access requests to said RTSP multimedia sequences, from said receivers (2), - determining and controlling in real time the activity levels of said servers (3), - selecting at least one server (3) from said servers (3) according to said requests (1) and said 25 levels of activity of said servers, - ordering said servers thus selected the broadcast (5) of said multimedia sequences to said receivers (2), via said communication network (7), in particular of the Internet or ASM type, so that the server manager ensures the control and continuity of the broadcast of multimedia sequences; said management server (8) further comprising computer encryption means for encrypting said multimedia sequences and said requests by means of protocols, in particular of IPsec, SSL, TLS type; said computer means of encryption being intended to: - ensure the confidentiality and the integrity of the reception of said requests and the broadcasting of said multimedia sequences, accelerate the transition times between multimedia sequences transmitted by different servers (3).