Abstract: A method for coding or decoding a spatial direction of a sound source, in which a spherical quantization dictionary is defined on a 3D sphere by coding elevation and azimuth, giving at least one coded elevation index (i) on a number of elevation levels (N?) and a number of points per level (Ny?(i)) determined on the basis of two successive cumulative cardinality values (cumN (i), cumN (i?1)), the cumulative cardinality value (cumN(i)) being representative of a number of points proportional to a total number of points and according to the area of a spherical region comprising at least one region delimited by the upper horizontal plane (?=(i+½)??) of the positive elevation level of the coded elevation index (i) and a lower horizontal plane of the sphere.

Abstract: Encoding at least one unit quaternion representing a rotation matrix used for coding a multichannel signal represented by an input point on a 4-dimensional sphere by encoding 3 spherical coordinates of the input point. The method includes sequential scalar quantization of the 3 spherical coordinates in order to obtain at most 4 candidates at the end of the sequential scalar quantization of the 3 coordinates; selecting the best candidate which minimizes a distance between the input point and the at most 4 candidates; determining the separate quantization indices resulting from the sequential scalar quantization of the spherical coordinates of the best candidate; determining a global quantization index by adding at least one item of cardinality information to the quantization index of a spherical coordinate; and coding of the global quantization index of said best candidate. A corresponding decoding method, an encoding device and a decoding device are also provided.

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 for encoding an input point on an n-dimensional sphere by encoding n?1 spherical coordinates of said input point. The method includes sequential scalar quantization of the n?1 spherical coordinates in order to obtain at most 2n-2 candidates at the end of the sequential scalar quantization of the n?1 coordinates, and subsequently selecting the best candidate which minimizes a distance between the input point and the at most 2n-2 candidates, and determining the separate quantization indices resulting from the sequential scalar quantization of the spherical coordinates of the best candidate and sequentially encoding the separate quantization indices of the best candidate. A corresponding decoding method, an encoding device and a decoding device are also provided.

Abstract: A method for encoding audio signals forming in time a succession of frames of samples, in each of n channels of an ambisonic representation of order higher than 0. The method includes: determining, for the current frame to be encoded, the binary value indicating an active or inactive mode of a decorrelation processing operation to be applied to the signals of the current frame and encoding this value into the bitstream; in the case where the mode is determined to be active, encoding into the bitstream decorrelation-processing information; generating an output signal to be encoded into the bitstream, depending on the mode determined for the current frame and the mode determined for the preceding frame. A corresponding decoding method is provided, as well as encoding and decoding devices implementing the respective encoding and decoding methods.

Abstract: A method for encoding an audio signal. The method includes: decomposing the audio signal into at least amplitude components and sign or phase components; analyzing the amplitude components, using a neural network-based autoencoder, in order to obtain a latent space representative of the amplitude components of the audio signal; encoding the latent space obtained; encoding at least some of the sign or phase components. A corresponding decoding method, as well as to encoding and decoding devices implementing the respective encoding and decoding methods are also provided.

Abstract: A method for coding or decoding a spatial direction of a sound source, in which a spherical quantization dictionary is defined on a 3D sphere by coding elevation and azimuth, giving at least one coded elevation index (i) on a number of elevation levels (N?) and a number of points per level (Ny?(i)) determined on the basis of two successive cumulative cardinality values (cumN (i), cumN (i?1)), the cumulative cardinality value (cumN(i)) being representative of a number of points proportional to a total number of points and according to the area of a spherical region comprising at least one region delimited by the upper horizontal plane (?=(i+½)??) of the positive elevation level of the coded elevation index (i) and a lower horizontal plane of the sphere.

Abstract: A method for encoding an input point on an n-dimensional sphere by encoding n-1 spherical coordinates of said input point. The method includes sequential scalar quantization of the n-1 spherical coordinates in order to obtain at most 2n-2 candidates at the end of the sequential scalar quantization of the n-1 coordinates, and subsequently selecting the best candidate which minimizes a distance between the input point and the at most 2n-2 candidates, and determining the separate quantization indices resulting from the sequential scalar quantization of the spherical coordinates of the best candidate and sequentially encoding the separate quantization indices of the best candidate. A corresponding decoding method, an encoding device and a decoding device are also provided.

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 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 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 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: 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: 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 for resampling an audio-frequency signal with an output sampling frequency, for a current signal frame. The method is used when the preceding frame is sampled at a first sampling frequency which is different from a second sampling frequency of the current frame. The method includes: determining a first and second segments of the signal by adding samples at zero at the end of stored samples of the preceding frame and at the start of samples of the current frame, respectively; obtaining the first resampled segment and the second resampled segment by applying at least one resampling filter respectively to the first segment resampling the first frequency at the output frequency, and to the second segment resampling the second frequency at the output frequency; and combining the overlapping portion of the first and second resampled segments to obtain at least one portion of the resampled current frame.

Abstract: A method and apparatus are provided for controlling the shaping of encoding noise during the ADPCM encoding of a digital audio input signal. The noise-shaping is carried out through the use of feedback that comprises filtering noise. The method includes the following steps: obtaining a parameter for indicating a high spectral dynamic range of the signal, the parameter indicating a risk of instability of the feedback; detecting a risk of instability by comparing the indication parameter to at least one predetermined threshold; limiting the feedback in the event that a risk of instability is detected; and gradually reactivating the feedback over a predetermined number of frames subsequent to the current frame for which the feedback is limited. Also provided is an encoder with feedback, including a control module implementing the control method as described.

Abstract: A method and apparatus for the parametric encoding of a stereo digital-audio signal. The method includes encoding a mono signal produced by downmixing applied to the stereo signal and encoding spatialization information of the stereo signal. Downmixing includes determining, for a predetermined set of frequency sub-bands, a phase difference between two stereo channels; obtaining an intermediate channel by rotating a first predetermined channel of the stereo signal through an angle obtained by reducing the phase difference; determining the phase of the mono signal from the phase of the signal that is the sum of the intermediate channel and the second stereo signal, and from a phase difference between, on the one hand, the signal that is the sum of the intermediate channel and the second channel and, on the other hand, the second channel of the stereo signal. Also provided are a decoding method, an encoder and a decoder.

Abstract: An encoder and a method for encoding a digital signal are provided. The method includes encoding a preceding frame of samples of the digital signal according to a predictive encoding process, and encoding a current frame of samples of the digital signal according to a transform encoding process. The method is implemented such that a first portion of the current frame is also encoded by predictive encoding that is limited relative to the predictive encoding of the preceding frame by reusing at least one parameter of the predictive encoding of the preceding frame and only encoding the parameters of said first portion of the current frame that are not reused. A decoder and a decoding method are also provided, which correspond to the described encoding method.