Abstract: A method for encoding a multichannel sound signal, a corresponding decoding method, an encoding device and a decoding device. The encoding method includes: forming a transformation matrix in the form of a rotation matrix to be applied to the input signals; quantifying the rotation matrix; and encoding the transformed signals after application of the rotation matrix. The quantifying of the rotation matrix includes the following operations: converting the rotation matrix in the quaternion domain with at least one first quaternion; forcing the first quaternion to have a positive component; converting the at least one first quaternion into spherical coordinates, one of the spherical coordinates being associated with the forced positive component of the first quaternion; and quantifying the resulting rotating spherical coordinates, the spherical coordinate associated with the forced positive component of the first quaternion being quantified in a half-length interval.

Abstract: A method and device for compressing audio signals forming, over time, a succession of sample frames, in each of N channels of an ambisonic representation of order higher than 0. The method includes: forming, based on the channels and for a current frame, a matrix of inter-channel covariance, and searching for eigenvectors of the covariance matrix with a view to obtaining a matrix of eigenvectors; testing the matrix of eigenvectors to verify that it represents a rotation in an N-dimensional space, and if not, correcting the matrix of eigenvectors until a rotation matrix is obtained, for the current frame; and applying the rotation matrix to the signals of the N channels before separate-channel encoding of the signals.

Abstract: A method for optimised coding of a multichannel sound signal. The method includes: coding at least one audio signal channel from the original multichannel signal; dividing the original multichannel signal into frequency sub-hands; determining one covariance matrix for each frequency sub-band, representative of a spatial image of the original multichannel signal; decomposing the predetermined covariance matrices into eigenvalues; coding by quantisation of the parameters from the decomposition into eigenvalues including both eigenvalues and eigenvectors. Also provided are a decoding method for decoding the parameters from the decomposition into eigenvalues of the covariance matrix of the original multichannel signal, and coding and decoding devices implementing the respective methods.

Abstract: A method of parametric coding of a multichannel digital audio signal including coding a signal arising from a channels reduction processing applied to the multichannel signal and coding spatialization information of the multichannel signal. The method includes the following acts: extraction of a plurality of items of spatialization information of the multichannel signal; obtaining at least one representation model of the extracted spatialization information; determination of at least one angle parameter of a model obtained; coding the at least one determined angle parameter so as to code the spatialization information extracted during the coding of spatialization information. Also provided are a method for decoding such a coded signal and corresponding coding and decoding devices.

Abstract: A method, receiver device and terminal for signaling an adaptation request to adapt a coding/decoding of real-time signals of a real-time communication session, from a receiver device to a sender device. The method is such that the adaptation request relates to a demand for aggregation and/or redundancy of frames, that it is generated according to the existence of a signaling parameter arising from a phase of negotiation of codecs used during initialization of the communication session and in that it is transported via a real-time protocol of RTP type.

Abstract: A method and device for determining a set of corrections to be made to a multichannel sound signal, in which the set of corrections is determined on the basis of an item of information representative of a spatial image of an original multichannel signal and an item of information representative of a spatial image of the original multichannel signal that has been coded and then decoded.

Abstract: A method for decoding a digital signal encoded using predictive coding and transform coding, comprising the following steps: predictive decoding of a preceding frame of the digital signal, encoded by a set of predictive coding parameters; detecting the loss of a current frame of the encoded digital signal; generating by prediction, from at least one predictive coding parameter encoding the preceding frame, a frame for replacing the current frame; generating by prediction, from at least one predictive coding parameter encoding the preceding frame, an additional segment of digital signal; temporarily storing said additional segment of digital signal.

Abstract: A method for adapting an encoding bitrate of real-time signals of a real-time communication session between sender devices and receiver devices of communication terminals. A sender device includes a multi-bitrate encoder using a set of discrete bitrates. The method includes a test step of increasing the encoding bitrate at the sender device by transmitting at least one redundant packet according to selected transmission parameters. A method is also provided for determining a request to adapt the encoding bitrate of real-time signals in order to implement a test of increasing the encoding bitrate at the sender device by transmitting at least one redundant packet according to selected transmission parameters. A sender device and a receiver device implementing the methods are provides as well as a terminal containing these devices.

Abstract: A method and device for compressing audio signals forming, over time, a succession of sample frames, in each of N channels of an ambisonic representation of order higher than 0. The method includes: forming, based on the channels and for a current frame, a matrix of inter-channel covariance, and searching for eigenvectors of the covariance matrix with a view to obtaining a matrix of eigenvectors; testing the matrix of eigenvectors to verify that it represents a rotation in an N-dimensional space, and if not, correcting the matrix of eigenvectors until a rotation matrix is obtained, for the current frame; and applying the rotation matrix to the signals of the N channels before separate-channel encoding of the signals.

Abstract: A method is provided for extending the frequency band of an audio signal during a decoding or improvement process. The method includes obtaining the decoded signal in a first frequency band, referred to as a low band. Tonal components and a surround signal are extracted from the signal from the low-band signal, and the tonal components and the surround signal are combined by adaptive mixing using energy-level control factors to obtain an audio signal, referred to as a combined signal. The low-band decoded signal before the extraction step or the combined signal after the combination step are extended over at least one second frequency band which is higher than the first frequency band. Also proved are a frequency-band extension device which implements the described method and a decoder including a device of this type.

Abstract: A method is provided for extending the frequency band of an audio signal during a decoding or improvement process. The method includes obtaining the decoded signal in a first frequency band, referred to as a low band. Tonal components and a surround signal are extracted from the signal from the low-band signal, and the tonal components and the surround signal are combined by adaptive mixing using energy-level control factors to obtain an audio signal, referred to as a combined signal. The low-band decoded signal before the extraction step or the combined signal after the combination step are extended over at least one second frequency band which is higher than the first frequency band. Also proved are a frequency-band extension device which implements the described method and a decoder including a device of this type.

Abstract: A method of determining a distribution of bits for coding a transition frame, said method being implemented in a coder/decoder for coding/decoding a digital signal, the transition frame being preceded by a predictive coded preceding frame, coding the transition frame comprising transform coding and predictive coding a single sub-frame of the transition frame, the method comprising the following steps: assigning a bit rate for predictive coding the transition sub-frame, said bit rate being equal to the minimum between the bit rate for transform coding the transition frame and a first predetermined bit rate value; determining a first number of bits allocated for predictive coding the transition sub-frame for said bit rate; and calculating a second number of bits allocated for transform coding the transition frame from the first number of bits and a number of bits available for coding the transition frame.

Abstract: A method for adapting an encoding bitrate of real-time signals of a real-time communication session between sender devices and receiver devices of communication terminals. A sender device includes a multi-bitrate encoder using a set of discrete bitrates. The method includes a test step of increasing the encoding bitrate at the sender device by transmitting at least one redundant packet according to selected transmission parameters. A method is also provided for determining a request to adapt the encoding bitrate of real-time signals in order to implement a test of increasing the encoding bitrate at the sender device by transmitting at least one redundant packet according to selected transmission parameters. A sender device and a receiver device implementing the methods are provides as well as a terminal containing these devices.

Abstract: Method and device for processing a video sequence containing a succession of images of one or more participant speakers, captured by a wide-angle camera. The method includes: capturing sound using a microphone having a plurality of sensors for capturing a sound field; processing the audio data captured by the microphone in order to determine at least one direction of origin of sound coming from a participant, relative to an optical axis of the wide-angle camera; generating a signal including data concerning the direction of origin of the sound relative to the optical axis of the camera, for the purpose of utilizing the signal when rendering the captured images by zooming into an area around the participant emitting the sound for which the direction of origin corresponds to the data of the signal.

Abstract: A method of parametric coding of a multichannel digital audio signal including coding a signal arising from a channels reduction processing applied to the multichannel signal and coding spatialization information of the multichannel signal. The method includes the following acts: extraction of a plurality of items of spatialization information of the multichannel signal; obtaining at least one representation model of the extracted spatialization information; determination of at least one angle parameter of a model obtained; coding the at least one determined angle parameter so as to code the spatialization information extracted during the coding of spatialization information. Also provided are a method for decoding such a coded signal and corresponding coding and decoding devices.

Abstract: A method and device are provided for determining an optimized scale factor to be applied to an excitation signal or a filter during a process for frequency band extension of an audio frequency signal. The band extension process includes decoding or extracting, in a first frequency band, an excitation signal and parameters of the first frequency band including coefficients of a linear prediction filter, generating an excitation signal extending over at least one second frequency band, filtering using a linear prediction filter for the second frequency band. The determination method includes determining an additional linear prediction filter, of a lower order than that of the linear prediction filter of the first frequency band, the coefficients of the additional filter being obtained from the parameters decoded or extracted from the first frequency and calculating the optimized scale factor as a function of at least the coefficients of the additional filter.

Abstract: A method and device are provided for determining an optimized scale factor to be applied to an excitation signal or a filter during a process for frequency band extension of an audio frequency signal. The band extension process includes decoding or extracting, in a first frequency band, an excitation signal and parameters of the first frequency band including coefficients of a linear prediction filter, generating an excitation signal extending over at least one second frequency band, filtering using a linear prediction filter for the second frequency band. The determination method includes determining an additional linear prediction filter, of a lower order than that of the linear prediction filter of the first frequency band, the coefficients of the additional filter being obtained from the parameters decoded or extracted from the first frequency and calculating the optimized scale factor as a function of at least the coefficients of the additional filter.

Abstract: A method of parametric coding of a multichannel digital audio signal including coding a signal arising from a channels reduction processing applied to the multichannel signal and coding spatialization information of the multichannel signal. The method includes the following acts: extraction of a plurality of items of spatialization information of the multichannel signal; obtaining at least one representation model of the extracted spatialization information; determination of at least one angle parameter of a model obtained; coding the at least one determined angle parameter so as to code the spatialization information extracted during the coding of spatialization information. Also provided are a method for decoding such a coded signal and corresponding coding and decoding devices.

Abstract: Method and device for processing a video sequence containing a succession of images of one or more participant speakers, captured by a wide-angle camera. The method includes: capturing sound using a microphone having a plurality of sensors for capturing a sound field; processing the audio data captured by the microphone in order to determine at least one direction of origin of sound coming from a participant, relative to an optical axis of the wide-angle camera; generating a signal including data concerning the direction of origin of the sound relative to the optical axis of the camera, for the purpose of utilizing the signal when rendering the captured images by zooming into an area around the participant emitting the sound for which the direction of origin corresponds to the data of the signal.

Abstract: A method is provided for extending the frequency band of an audio signal during a decoding or improvement process. The method includes obtaining the decoded signal in a first frequency band, referred to as a low band. Tonal components and a surround signal are extracted from the signal from the low-band signal, and the tonal components and the surround signal are combined by adaptive mixing using energy-level control factors to obtain an audio signal, referred to as a combined signal. The low-band decoded signal before the extraction step or the combined signal after the combination step are extended over at least one second frequency band which is higher than the first frequency band. Also proved are a frequency-band extension device which implements the described method and a decoder including a device of this type.