Abstract: A method and system are provided for reducing the peak factor in a multi-carrier communication system, the data being transmitted on m channels comprising, in the transmission of data in the form of a frame, a step in which a number d of desynchronization symbols are introduced at the start of each of the frames, the number d being chosen as a function of the transmission channel number concerned.

Abstract: Method for transmitting data in a transmission system, the data being transmitted in the form of packets including a compressed header field and a data field and according to a format suited to the transmission system comprising the following steps: recovering the data packet to be transmitted including a compressed header and useful data, identifying the header part from the useful-data part, applying a corrector coding which is selected at the level of the header, and providing the resulting new packet to the link layer, while also communicating the protection mode used, generating the link header according to the transmission format of the relevant transmission system integrating the mode of protection used, and the adaptation of the CRC checksum of the link layer, on reception, performing the error corrector decoding in two steps.

Abstract: Method of estimating the perceived quality of a video sequence at a maximum spatial resolution and a maximum temporal resolution, and at a lower spatial resolution and/or temporal resolution, said method including filtering said video sequence at the lower temporal resolution and/or the lower spatial resolution so as to produce a filtered video sequence at the maximum spatial and temporal resolutions; determining a reference sequence that is, at most, equal to the content of said video sequence at the maximum spatial and temporal resolutions; and calculating a metric of perceived quality of said video sequence at the lower temporal resolution and/or the lower spatial resolution.

Abstract: Method of estimating the perceived quality of a video sequence at a maximum spatial resolution and a maximum temporal resolution, and at a lower spatial resolution and/or temporal resolution, said method including filtering said video sequence at the lower temporal resolution and/or the lower spatial resolution so as to produce a filtered video sequence at the maximum spatial and temporal resolutions; determining a reference sequence that is, at most, equal to the content of said video sequence at the maximum spatial and temporal resolutions; and calculating a metric of perceived quality of said video sequence at the lower temporal resolution and/or the lower spatial resolution.

Abstract: Method of determining the coding parameters of a variable-resolution video stream by a video coder, said video stream including multiple resolution layers and being compressed so as to be transmitted at a given rate or a given quality through a heterogeneous network to multiple users, said method including a classification step to associate each resolution level with a group of users and to determine the optimal coding parameters for each resolution level as a function of the requirements of each group of users.

Abstract: A method for adaptive communication in an HF frequency band includes at least one of the following steps: the determination of a payload subband S that is available for a transmission in the HF band, the selection in the payload subband S of a set of n frequency channels of identical width according to a frequency allocation plan and the quality of the link of each of said channels, or the simultaneous transmission on the n frequency channels of a signal complying with an HF waveform.

Abstract: A method for transmitting multimedia data in an ad hoc network including receiving a packet on a radio interface, and if the node is not its destination, is copied into a local buffer Q while awaiting the verification of the packet, the packet is also uploaded to the top layers for on the one hand verification of its possible corruption and on the other hand optional storage in a local stack P of long duration with additional information about the data fragment. In the case where the transmission on the last hop before the current node has corrupted the packet, it is verified that the headers are intact so as to be able to route the packet appropriately, after having verified whether the stack P is present and whether it contains an intact version of the packet, in which case it is the intact payload which will be substituted for the erroneous payload in the buffer Q.

Abstract: A method allowing operating parameters, such as the compression ratio and/or the protection ratio for a multimedia data transmission channel to be determined, wherein it includes at least one step during which several values of sensitivity are determined for pairs of values fixed source bit-rate, desired compression ratio, a step where the different values obtained for an operating point of the fixed channel are compared with one another, and a step where the optimum sensitivity value is selected, the sensitivity value being defined taking the desired source bit-rate and the compression ratio into account.

Abstract: Procedure and device for shaping frames of a video sequence or group of pictures GOP using a mixing table adapted for arranging the frames of the highest importance regularly while leaving intervals between them, filling the intervals with frames of lesser importance, and coding the new sequence thus obtained.

Abstract: A method for encrypting data exchanged between an encoder and a decoder in a video system is disclosed. A set of bits which, when encoded, do not have any influence upon the decoding stage, are determined during the encoding stage. At least one part or all of the bits selected in stage 1 is/are encoded prior to transmission to the decoding stage. The bit selection stage determines the parts of the flow of bits that only modify the contexts of the decoding process in an insignificant manner in the sense that the modification due to encryption does cause desynchronization or does not lead to non-compatible bit flows with regard to encoding contexts and visual impact. The present invention is used with H.264 encoders/decoders.

Abstract: A method for optimizing a video transmission, in a constrained environment using a video coder adapted for coding the video data to be transmitted, includes determining one or more compression parameters for the video coder considered to transmit the video data at a given throughput or for a given quality. The method defines and uses reference charts for the coder considered, and predicts for the part of the video sequence undergoing compression, using the reference charts, compression parameters to be used, such as the quantization interval, by selecting a chart for which the targeted range of throughput or of quality is the closest in distance to the part of the sequence to be compressed, while complying with a given margin, and updates with an iterative method the prediction step to converge on the best choice of parameterization. The iteration includes at least one compression step followed by a verification step, to compress the video data to be transmitted with the parameters.

Abstract: A method for transmitting multimedia data in an ad hoc network including receiving a packet on a radio interface, and if the node is not its destination, is copied into a local buffer Q while awaiting the verification of the packet, the packet is also uploaded to the top layers for on the one hand verification of its possible corruption and on the other hand optional storage in a local stack P of long duration with additional information about the data fragment. In the case where the transmission on the last hop before the current node has corrupted the packet, it is verified that the headers are intact so as to be able to route the packet appropriately, after having verified whether the stack P is present and whether it contains an intact version of the packet, in which case it is the intact payload which will be substituted for the erroneous payload in the buffer Q.

Abstract: Method for transmitting data in a transmission system, the data being transmitted in the form of packets including a compressed header field and a data field and according to a format suited to the transmission system comprising the following steps: recovering the data packet to be transmitted including a compressed header and useful data, identifying the header part from the useful-data part, applying a corrector coding which is selected at the level of the header, and providing the resulting new packet to the link layer, while also communicating the protection mode used, generating the link header according to the transmission format of the relevant transmission system integrating the mode of protection used, and the adaptation of the CRC checksum of the link layer, on reception, performing the error corrector decoding in two steps.

Abstract: A method allowing operating parameters, such as the compression ratio and/or the protection ratio for a multimedia data transmission channel to be determined, wherein it includes at least one step during which several values of sensitivity are determined for pairs of values fixed source bit-rate, desired compression ratio, a step where the different values obtained for an operating point of the fixed channel are compared with one another, and a step where the optimum sensitivity value is selected, the sensitivity value being defined taking the desired source bit-rate and the compression ratio into account.

Abstract: A method for protecting multimedia data encoded by the H.264 standard, the data being encapsulated in a structure of the network abstraction layer or NAL type, characterized in that the user inserts at least one redundancy NAL containing the error-correcting code used for transmitting the data.

Abstract: Procedure and device for shaping frames of a video sequence or group of pictures GOP using a mixing table adapted for arranging the frames of the highest importance regularly while leaving intervals between them, filling the intervals with frames of lesser importance, and coding the new sequence thus obtained.

Abstract: A method for encrypting data exchanged between an encoder and a decoder in a video system is disclosed. A set of bits which, when encoded, do not have any influence upon the decoding stage, are determined during the encoding stage. At least one part or all of the bits selected in stage 1 is/are encoded prior to transmission to the decoding stage. The bit selection stage determines the parts of the flow of bits that only modify the contexts of the decoding process in an insignificant manner in the sense that the modification due to encryption does cause desynchronization or does not lead to non-compatible bit flows with regard to encoding contexts and visual impact. The present invention is used with H.264 encoders/decoders.