Abstract: An encoder extracts motion vectors from a frame I(t?1) preceding the frame I(t) being encoded, to create a motion complexity map and creating an irregular grid of cells, the sizes of the cells based on the complexity of motion in the frame at a respective position. This gives a motion vector field made up of an irregular grid of differently-sized cells, each cell having associated with it a motion vector. The motion vectors are transmitted to the decoder as auxiliary information along with the usual motion prediction information. The decoder receives the motion prediction information, with a slice missing, and the auxiliary information. The decoder rebuilds the irregular grid for frame I(t) based on the frame I(t?1) similarly, and fills the cells with the motion vectors from the auxiliary information, thus recreating an estimated motion vector field for the current frame I(t) for subsequent error concealment/decoding/displaying.

Abstract: A method of processing a coded data stream of a current image on a receiving device, the data stream being organized into packets, comprises a step of detecting a lost packet. It further comprises: a step of estimating, prior to the decoding of the current image, an importance criterion of the lost packet, the importance criterion being determined from at least one decoded preceding image; and a step of requesting retransmission of the lost packet depending on said estimated importance criterion. Use in particular for improving the transmission of a video.

Abstract: The disclosure provides a method of decoding a sequence of encoded digital frames encoded by an encoder using a format applying block-based prediction. For the decoding of an encoded digital frame which comprises a missing area, the method includes obtaining additional data associated with at least one block of the encoded digital frame. Using the obtained additional data, for at least one block of the missing area, information identifying one type of predictor in a predetermined list of types of predictor is obtained. A reconstruction method for the at least one block of the missing area is selected using the information identifying one type of predictor.

Abstract: The method of transmission of a datastream representing a sequence of images over a network in which the quantity of information that may be sent per unit of time varies substantially cyclically, said transmission extending over a plurality of cycles, comprises: a step (805 to 807, 809, 810) of determining times for which the quantity of information that may be sent per unit of time over the network is greater, and respectively less, than its average, on the basis of the substantially cyclical past variation in said quantity of information and a step (801 to 805, 812 to 816) of sending over said network, at said times, images corresponding to a greater, and respectively smaller, quantity of information than the average of the images. During the determining step, a period of cyclical variation of the quantity of information that may be sent over the network is determined.

Abstract: The invention concerns the decoding of a digital signal comprising at least one encoded digital image, a digital image being represented by a plurality of samples. The decoding method comprises, when a part of one said encoded digital image to be decoded is missing, applying a first decoding to the encoded digital image having the missing part so as to obtain a first decoded image, the first decoding involving setting a missing sample, being one of said samples in said missing part, to a first value. A second decoding is applied to said first decoded image using additional data, derived by the encoder from at least part of the encoded digital image and usable during decoding to correct the encoded digital image, to obtain a partially corrected symbol representative of said sample, said partially corrected symbol comprising at least one unknown bit. Finally, a second value for said missing sample is obtained based upon said first value and said partially corrected symbol.

Abstract: To predict the transmission error rate in a stream of data packets transmitted between a server and at least one client in a communication network: the server sends at least one group of packets to the client; the client calculates a plurality of items of statistical information on the group of packets and transmits them to the server; the server analyzes the items of statistical information so as to obtain a network stability indicator; and the server calculates a prediction of the transmission error rate on the basis of the network stability indicator.

Abstract: In a method of encoding a video frame to be transmitted to a plurality of clients over a plurality of network connections, a set of parameters is associated with each connection. The method comprises: for each connection, determining a frame size that can be transported over the connection considering the associated set of parameters; and compressing the video frame to a target frame size based on the minimum of the plurality of determined frame sizes. This method advantageously provides an easy and straightforward way for selecting the appropriate parameters that need to be taken into account for controlling the rate of the generated bitstream, particularly when multiple parameters are associated with each connection.

Abstract: A method for adapting error protection in a communication network includes: a step of determining periods of time that are homogeneous as regards the distribution law of losses over the network, a step of classifying the homogeneous periods of time into at least two classes, on the basis of information representing losses over the network and/or representing a corresponding level of protection, during these periods of time, a step of determining a probability of alternation between two of said classes, and a step of selecting a protection strategy on the basis of said probability of alternation. A method of detecting transition between two states of a communication network corresponding to different loss rates of sent data includes: a step of determining a probability of transition, and a step of determining the existence of a transition on the basis of said probability.

Abstract: The method of verifying multimedia entities according to the invention to determine whether a first multimedia entity matches a second multimedia entity, is characterized in that it comprises a step of selecting from a plurality of second multimedia entities, by a content-based search, a set of second multimedia entities close to the first multimedia entity, and a step of deciding as to at least one match between the first multimedia entity and at least one second multimedia entity of the set of second multimedia entities, based on a comparison between the first multimedia entity and the second multimedia entities of the set.

Abstract: A sequence of digital images encoded according to a predictive format is decoded using encoded auxiliary data which is representative of at least part of the sequence of digital images. A current encoded image, received with at least one detected error, is decoded. The decoding includes applying an error concealment decoding on at least part of the current encoded image containing such a detected error to obtain a first decoded image. An item of information representative of reconstruction errors is obtained based upon a reconstruction confidence of the error concealment decoding for at least one pixel of the error-containing part of the current image. The encoded auxiliary data and the first decoded image are processed based upon the item of information representative of reconstruction errors to obtain corrected auxiliary data. The first decoded image is modified to obtain a second decoded image based upon the corrected auxiliary data.

Abstract: The invention concerns a method for decoding a video sequence encoded according to a predictive format, which video sequence includes predicted images containing encoded residual data representing differences between the respective predicted image and a respective reference image in the video sequence. The method of the invention comprises, applying to a current image which contains at least one area which is to be reconstructed, the steps of: obtaining (E605) projected residual data for said at least one area to be reconstructed, from residual data of at least one image predicted from the current image, corresponding to a temporal projection of at least part of the at least one area to be reconstructed onto said at least one image predicted from the current image; and reconstructing (E606) at least part of said at least one area using the projected residual data obtained.

Abstract: The invention concerns a method for decoding a video sequence encoded according to a predictive format, which video sequence includes predicted images containing encoded residual data representing differences between the respective predicted image and a respective reference image in the video sequence. The method comprises, for a current predicted image of the video sequence, the steps of: determining (E51) at least one first area of the current predicted image according to meeting of a predetermined criterion; for at least part of the determined at least one first area, applying an error concealment method (E514), said error concealment method using residual data of the current predicted image relative to said part.

Abstract: The video coding method comprises a step (1001) of determining a motion vector for each of a plurality of blocks of a picture from a reference picture. The method then performs a step (1006 to 1010) of selecting at least one first block in said plurality of blocks, according to the difference between a first motion vector and a second motion vector, wherein the first motion vector is the motion vector associated with said first block, and the second motion vector is a motion vector relating to a second block, which second block is located in the same picture at a position relative to the first block determined by the first motion vector. The method then performs a step (1012) of coding at least one non-selected block with a first coding mode, and a step (1012) of coding at least one first selected block with a second coding mode different from the first coding mode.

Abstract: To predict the transmission error rate in a stream of data packets transmitted between a server and at least one client in a communication network: the server sends at least one group of packets to the client; the client calculates a plurality of items of statistical information on the group of packets and transmits them to the server; the server analyzes the items of statistical information so as to obtain a network stability indicator; and the server calculates a prediction of the transmission error rate on the basis of the network stability indicator.

Abstract: A method of processing a coded data stream of a current image on a receiving device, the data stream being organized into packets, comprises a step of detecting a lost packet. It further comprises: a step of estimating, prior to the decoding of the current image, an importance criterion of the lost packet, the importance criterion being determined from at least one decoded preceding image; and a step of requesting retransmission of the lost packet depending on said estimated importance criterion. Use in particular for improving the transmission of a video.

Abstract: A method of processing a stream of coded data before decoding comprises a step of detecting missing or erroneous data in the stream of coded data. It comprises a step of generating a series of data ready for decoding formed from the stream of coded data, and a series of additional data supplying information representing the position of the missing or erroneous data detected.

Abstract: The invention concerns a method of adapting a temporal frequency of a sequence of video images for the purpose of its transmission over a communication network, characterized in that images of the sequence having been sampled at a temporal frequency f1. The method and device for adapting a temporal frequency of a sequence of video images, the method comprises a step of deciding as to the carrying out of a step of simulating a coding of images of the video sequence sampled at a temporal frequency f2>f1, for the purpose of determining whether the sampling temporal frequency fa method and device for adapting a temporal frequency f1 of the sequence can be increased, the decision being taken on the basis of at least one criterion (409; 513) relative to the resources of a communication apparatus able to perform the simulation step (412; 516) and/or on the basis of the evolution over time of the characteristics of the video sequence and/or of the network (512, 515).

Abstract: The invention relates to a method of inserting a message into digital data representative of physical quantities, the message including ordered symbols, including the steps of: segmenting (E2) the data into regions, associating (E3) at least one region with each symbol to be inserted, characterized in that, for each region into which a symbol in question is to be inserted, it includes the steps of: determining (E7) a pseudo-random function, from a key which depends: on an initial key, and on the length of the message, modulating (E8) the symbol in question by the previously determined pseudo-random function in order to supply a pseudo-random sequence, adding (E10) the pseudo-random sequence to the region in question.

Abstract: The method of transmission of a datastream representing a sequence of images over a network in which the quantity of information that may be sent per unit of time varies substantially cyclically, said transmission extending over a plurality of cycles, comprises: a step (805 to 807, 809, 810) of determining times for which the quantity of information that may be sent per unit of time over the network is greater, and respectively less, than its average, on the basis of the substantially cyclical past variation in said quantity of information and a step (801 to 805, 812 to 816) of sending over said network, at said times, images corresponding to a greater, and respectively smaller, quantity of information than the average of the images. During the determining step, a period of cyclical variation of the quantity of information that may be sent over the network is determined.

Abstract: The invention concerns a method of inserting a message in an image, the message comprising binary symbols which are each referenced by an index, characterized in that it comprises, for a coefficient (Yn) of the image, the steps of: determining (E9) a watermarked value (Y?n) of the coefficient, according to the binary value (b) of a symbol of the message and according to the index (i) of the symbol, inserting (E11) the watermarked value in place of the value of the coefficient.