France Telecom

Orange

Koninklijke Philips Corporation N.v.

Balazs Kovesi

Stéphane Ragot

Stephane Ragot

David Virette

Claude Lamblin

Dominique Massaloux

Alain Le Guyader

Pierrick Philippe

David Deleam

Jerome Daniel

Arnault Nagle

Pierre Berthet

Claude Marro

Jérôme Daniel

Thi Minh Nguyet Hoang

Jean-Luc Garcia

Adrien Cormier

Pierrick Phlippe

A method and device for resampling an audio frequency signal in an audio frequency signal coding or decoding. The method includes the following acts for each signal block to be resampled: determining, by adaptive linear prediction, a number of future signal samples, this number being defined as a function of a chosen resampling delay; constructing a resampling support vector from at least samples of the current block and determined future signal samples; applying a resampling filter to the samples of the resampling support vector.

Resampling an audio signal for low-delay encoding/decoding

A method is provided for resampling an audio-frequency signal in an audio-frequency signal encoding or decoding operation. The resampling is carried out by a method of interpolation of an order greater than one. The method is such that the interpolated samples are obtained by calculating a weighted average of possible interpolation values calculated over a plurality of intervals covering the time location of the sample to be interpolated. A resampling device is provided, which implements the method, and also an encoder and decoder including at least one resampling device.

Resampling of an audio signal by interpolation for low-delay encoding/decoding

A method and apparatus are provided for updating post-processing states applied to a decoded audio signal. The method is such that, for a current decoded signal frame, sampled at a different sampling frequency from the preceding frame, it includes the following acts: obtaining a past decoded signal, stored for the preceding frame; re-sampling by interpolation of the past decoded signal obtained; using the re-sampled past decoded signal as a memory for post-processing the current frame. A decoding method is also provided, which includes updating post-processing states.

Update of post-processing states with variable sampling frequency according to the frame

The invention relates to a method for mixing a plurality of audio streams coded according to a frequency sub-band coding, comprising the steps for decoding (E) a part of the coded streams over at least a first frequency sub-band, for summing (E) the streams thus decoded so as to form at least a first mixed stream. The method is such that it comprises the steps for detection (E), over at least a second frequency sub-band different from the at least first sub-band, of the presence of a predetermined frequency band in the plurality of coded audio streams and for summing (E) the decoded audio streams (E) for which the presence of the predetermined frequency band has been detected, over said at least a second sub-band, so as to form at least a second mixed stream. The invention also relates to a mixing device implementing the method described and may be integrated into a conference bridge, a communications terminal or a communications gateway.

Optimized mixing of audio streams encoded by sub-band encoding

A method is provided for processing attenuation of pre-echo in a digital audio signal decoded by transform decoding. The method includes the following acts: decomposition of the decoded signal into at least two sub-signals according to a pre-determined decomposition criterion; calculation of attenuation factors per sub-signal and per sample of a previously determined pre-echo zone; attenuation of pre-echo in the pre-echo zone of each of the sub-signals by applying attenuation factors to the sub-signals; and production of the attenuated signal by addition of the attenuated sub-signals. Also provided are a processing device implementing the acts of the described method, and a decoder including such a device.

Effective attenuation of pre-echoes in a digital audio signal

A method for discriminating and attenuating pre-echo in a digital audio signal and generated from transform coding. The method includes the following acts in which, for a current frame broken down into sub-blocks, the low-energy sub-blocks precede a sub-block in which a transition or attack is detected, and determine a pre-echo area in which a pre-echo attenuation process is carried out. In the event that an attack is detected from the sub-block of the current frame, the method includes: calculating an energy leading coefficient for at least two sub-blocks of the current frame preceding the sub-block in which an attack is detected; comparing the leading coefficient to a predefined threshold; and inhibiting the pre-echo attenuation process in the pre-echo area in the event that the calculated leading coefficient is lower than the predefined threshold. Also provided are a discrimination and attenuation device implementing the acts of the method described and a decoder including such a device.

Discrimination and attenuation of pre echoes in a digital audio signal

A method for processing an encoded audio signal in a binary stream by MICDA predictive coding. The method includes the following steps: determining a signal assessed from quantification indices of the binary stream; determining unencoded parameters representative of the audio signal from the assessed signal; and processing the encoded audio signal using the determined parameters. Also provided is a device implementing the method.

Processing in the encoded domain of an audio signal encoded by ADPCM coding

The invention relates to a method for combining a plurality of audio streams encoded by frequency sub-band encoding, comprising the following steps: decoding (E) a portion of the encoded streams over at least one frequency sub-band; combining (E) the streams thus encoded to form a mixed stream; selecting (E), from among the plurality of encoded audio streams, at least one encoded replication stream, over at least one frequency sub-band that is different from that of the decoding step. The method is such that the selection of the at least one encoded replication stream is carried out according to a criterion which takes into consideration the presence of a predetermined frequency band in the encoded stream (E). The invention also relates to a device which implements the described method and can be integrated into a conference bridge, a communication terminal or a communication gateway.

Optimized partial mixing of audio streams encoded by sub-band encoding

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.

Resampling of an audio signal interrupted with a variable sampling frequency according to the frame

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 is provided for processing pre-echo attenuation in a digital audio signal generated from a transform coding, wherein, at the decoding point, the method includes: detection of a position of attack in the decoded signal; determination of a pre-echo region preceding the position of attack detected in the decoded signal; calculation of attenuation factors per sub-block of the pre-echo region, according to at least the frame wherein the attack has been detected and the preceding frame; and pre-echo attenuation in the sub-blocks of the pre-echo region by the corresponding damping factors. The method also includes application of a filter for the spectral shaping of the pre-echo region on the current frame up to the detected position of the attack. A device and a decoder including the device are also proved for implementing the method.

Effective pre-echo attenuation in a digital audio signal

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 parametric coding method and apparatus are provided for coding a multichannel digital audio signal. The method includes a coding step for coding a signal from a channel reduction matrixing of the multichannel signal. The coding method also includes: obtaining, for each frame of predetermined length, spatial information parameters of the multichannel signal; dividing the spatial information parameters into a plurality of blocks of parameters; selecting a block of parameters as a function of the index of the current frame; and coding the block of parameters selected for the current frame.

Optimized low-bit rate parametric coding/decoding

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.

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Balazs Kovesi