France Telecom

Orange

Koninklijke Philips Corporation N.v.

Stéphane Ragot

Balazs Kovesi

David Virette

Julien Faure

Claude Lamblin

Pierre Berthet

Cyril Guillaume

Marc Emerit

Magdalena Kaniewska

Alain Le Guyader

Jerome Daniel

Jérôme Daniel

Bertrand Fatus

Romain Trilling

Najmeddine Majed

Thi Minh Nguyet Hoang

Andrzej Zielinski

Pierre Mahe

Pierre Clément Mahe

Robert Warzocha

Mohamed Yaoumi

Robert Kolodynski

Jérôme Dufour

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.

Optimized encoding of rotation matrices for encoding a multichannel audio signal

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 2candidates 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 2candidates, 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.

Optimised spherical vector quantisation

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.

Determining corrections to be applied to a multichannel audio signal, associated coding and decoding

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.

Spatialized audio coding with interpolation and quantization of rotations

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.

Processing of data of a video sequence in order to zoom to a speaker detected in the sequence

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.

Controlling a noise-shaping feedback loop in a digital audio signal encoder avoiding instability risk of the feedback

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.

Stereo parametric coding/decoding for channels in phase opposition

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.

Low-delay sound-encoding alternating between predictive encoding and transform encoding

A method is provided for hierarchical coding of a digital audio signal comprising, for a current frame of the input signal: a core coding, delivering a scalar quantization index for each sample of the current frame and at least one enhancement coding delivering indices of scalar quantization for each coded sample of an enhancement signal. The enhancement coding comprises a step of obtaining a filter for shaping the coding noise used to determine a target signal and in that the indices of scalar quantization of said enhancement signal are determined by minimizing the error between a set of possible values of scalar quantization and said target signal. The coding method can also comprise a shaping of the coding noise for the core bitrate coding. A coder implementing the coding method is also provided.

Coding with noise shaping in a hierarchical coder

A method of hierarchical coding of a digital audio frequency input signal into several frequency sub-bands, including a core coding of the input signal according to a first throughput and at least one enhancement coding of higher throughput, of a residual signal. The core coding uses a binary allocation according to an energy criterion. The method includes for the enhancement coding: calculating a frequency-based masking threshold for at least part of the frequency bands processed by the enhancement coding; determining a perceptual importance per frequency sub-band as a function of the masking threshold and as a function of the number of bits allocated for the core coding; binary allocation of bits in the frequency sub-bands processed by the enhancement coding, as a function of the perceptual importance determined; and coding the residual signal according to the bit allocation. Also provided are a decoding method, a coder and a decoder.

Coding/decoding of digital audio signals

The invention concerns an encoder for an input audio signal (S(z)) comprising a combination module combining the input audio signal with an intermediate counter-reaction signal forming a modified input signal and a quantification module scalable for the rate () of said modified input signal, delivering a binary raster of quantification indexes of a predetermined rate. This encoder is such that it comprises: a reverse quantification module () of a part of the quantification indexes of the binary raster corresponding to the indexes of a rate lower than the predetermined rate, for predetermining a reconstructed signal (S(z)), a module for determining () a quantification noise (Q(z)) derived from at least quantification modules and reverse quantification modules in series, a determination module () for a filtering function of the quantification noise from said reconstructed signal and a filtering module fit for applying () said filtering function to said quantification noise in order to obtain said intermediary counter-reaction signal. The invention also relates to an encoding method applied by the described encoder and a corresponding decoding method applied by a decoder.

Methods and apparatus for coding digital audio signals using a filtered quantizing noise

A method is provided for attenuating pre-echoes in a digital audio signal generated from a transform encoding, comprising, upon decoding and for a current frame of said digital audio signal: defining a concatenated signal from at least the reconstructed signal of the current frame, dividing said concatenated signal into subunits of samples having a predetermined length, calculating the time envelope of the concatenated signal, detecting the transition of the time envelope towards a high-energy area, determining the low-energy sub-units preceding a subunit in which a transition has been detected, and an attenuation step in said determined subunits. The attenuation is carried out according to an attenuation factor calculated for each of the determined subunits, based on the time envelope of the concatenated signal. The invention also relates to a device for implementing said method, and to a decoder including such a device.

Pre-echo attenuation in a digital audio signal

A method of bitrate switching on decoding an audio signal coded by a audio coding system, said decoding comprising a post-processing step depending on the bitrate. On switching from an initial bitrate to a final bitrate, said method includes a transition step of continuous change from a signal at the initial bitrate to a signal at the final bitrate, one or both of said signals being post-processed. Application to transmission of VoIP speech and/or audio signals in data packet networks.

Method for switching rate and bandwidth scalable audio decoding rate

The present invention relates to a method of transmission error concealment in a digital signal split up into a plurality of successive frames associated with different time intervals in which, on reception, the signal might comprise erased frames and valid frames and in order to replace at least the first erased frame (N) after a valid frame, at least two steps are performed, a first step (E) of preparation not producing any missing sample and comprising at least one analysis of a valid decoded signal and a second step (E) of concealment producing the missing samples of the signal corresponding to said erased frame. The first step and the second step are executed in different time intervals. The invention relates also to a device of concealment implementing the method according to the invention as well as a decoder comprising such a device. The invention allows the distribution of the error concealment complexity on different time intervals.

Transmission error dissimulation in a digital signal with complexity distribution

The invention relates to a method for scalar quantization-based coding of the samples of a digital audio signal (S), the samples being coded over a pre-determined number of bits in order to obtain a binary frame of quantization indices (I), the coding being carried out according to an amplitude compression law, where a pre-determined number of least significant bits are not taken into account in the binary frame of quantization indices. The coding method comprises the steps for storing () at least a part of the least significant bits that are not taken into account in the quantization index binary frame and for determination () of an enhancement bit stream (I) comprising at least one bit thus stored. The invention also relates to an associated decoding method which comprises the steps for receiving () an enhancement bit stream (I') comprising one or more extension bits and for concatenation () of the extension bits behind the bits coming from the binary frame in order to obtain a decoded audio signal. The invention also relates to the coder and decoder implementing these methods.

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Lannion, France

Stéphane Ragot