France Telecom

Orange

France Telecom Sa

Claude Lamblin

Balazs Kovesi

Arnault Nagle

David Virette

Stéphane Ragot

Mohamed Ghenania

Dominique Massaloux

Pierrick Philippe

Yannick Mahieux

Abdellatif Benjelloun Touimi

Romain Trilling

Adrien Cormier

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 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 is provided for detecting a predetermined frequency band in an audio data signal which has previously been coded according to a succession of data blocks, among which at least certain blocks contain respectively at least one set of spectral parameters representing a linear prediction filter. Such a method of detection implements, for a current block among the at least certain blocks and for which at least a plurality of spectral parameters of the set have been previously decoded, acts of: determining, among the plurality of previously decoded spectral parameters, the index of the first spectral parameter closest to a threshold frequency; calculating at least one criterion on the basis of the determined index; and deciding whether the predetermined frequency band is detected in the current block, as a function of the criterion calculated.

Method of detecting a predetermined frequency band in an audio data signal, detection device and computer program corresponding thereto

A method of coding/decoding of a digital audio signal comprising a succession of consecutive blocks of data, on the basis of a predictive filter. A modified predictive filter is used for the coding of at least one current block, the modified filter being constructed by the combination of: a rear filter calculated for a past block, preceding the current block, and enrichment parameters for the rear filter, which are determined as a function of the signal in the current block and comprising the coefficients of a modifying filter.

Adaptive linear predictive coding/decoding

A binary allocation in a hierarchical coding/decoding comprising a coding/decoding of a digital signal enhancement layer. The signal comprises a succession of L samples, each sample being represented by a mantissa and an exponent. The method comprises the allocation of a predetermined number Nof enhancement bits to a part at least of the L samples of highest exponent values. In particular, the method comprises the steps: a) enumerating the exponents of the L samples each having a given value, b) calculating at least one aggregate of enumerations of exponents by decreasing values of exponent until the predetermined number Nis approximated from above, for c) determining a threshold value of largest exponent iexp0 of sample for which no more enhancement bit is available, and allocating the Nenhancement bits, according to chosen rules, to the samples whose exponent is greater than the aforesaid threshold value iexp.

Hierarchical coding

Disclosed is a system and method for implementing compression coding of audio signals, such as speech signals, using two long-term prediction (LTP) models. The method determines the parameters of a second long-term prediction model on the basis of the parameters of at least one first LTP model. The present invention is aimed at switching from an LTP model with a single coefficient (monotap) to an LTP model with several coefficients, (multitap) and vice versa, as well as at switching between two multitap LTP models. The complexity of the method may be adjusted, especially as a function of a desired compromise between a target complexity and a desired quality. A device for implementing the method according to the invention is, moreover, very useful for multiple codings in cascade (transcodings) or in parallel (multi-codings and multi-mode codings).

Method and device for carrying out optimal coding between two long-term prediction models

The invention aims at constructing improved dictionaries of CELP excitation vectors for coding/decoding digital audio signals. Usually, each vector of dimension N comprises pulses capable of occupying N valid positions. The invention concerns the construction of dictionaries with particular structure by: providing a common sequence of pulses forming a base pattern; and assigning the base pattern to each excitation vector of the dictionary, based on one or more occurrences at one or more respective positions among said N valid positions. The invention also concerns a combination of dictionaries thus constructed with optionally standard multipulse dictionaries, by union or summation or cascading.

Coding/decoding of a digital audio signal, in CELP technique

The invention relates to the code conversion of digital signals, particularly voice signals, and in particular coding according to a second format from information obtained by carrying out a coding according to a first format. These first and second formats use LPC (linear predictive coding) short-term prediction models on digital signal sample blocks while using filters represented by respective LPC coefficients. The LPC coefficients of the second format are determined from an interpolation on the representative values of the LPC coefficients of at least the first format, between at least one given block and a preceding block. According to the invention, the interpolation (), is dynamically effected while selecting (), for each current block, at least one interpolation factor (&#x3b1;) among a preselection of factors according to a predetermined criterion such as a stationarity criterion of the digital signal ().

Method for adapting for an interoperability between short-term correlation models of digital signals

The invention relates to the encoding/decoding of digital signals, especially using permutation codes involving a calculation of combinatorial expressions. According to the invention, the combinatorial expressions are represented by prime factor power decompositions, and determined by a preliminary reading of pre-recorded representations of decompositions of selected integers.

Encoding/decoding of digital signals, especially in vector quantization with permutation codes

The invention relates to the encoding/decoding of digital signals, especially using transposition codes involving a calculation of combinatorial expressions. According to the invention, the combinatorial expressions are represented by prime factor power decompositions, and determined by a preliminary reading of pre-recorded representations of decompositions of selected whole numbers.

The invention relates to the compression coding of digital signals such as multimedia signals (audio or video), and more particularly a method for multiple coding, wherein several encoders each comprising a series of functional blocks receive an input signal in parallel. Accordingly, a method is provided in which, a) the functional blocks forming each encoder are identified, along with one or several functions carried out of each block, b) functions which are common to various encoders are itemized and c) said common functions are carried out definitively for a part of at least all of the encoders within at least one same calculation module.

Optimized multiple coding method

The invention relates to compression coding and/or decoding of digital signals, in particular by vector variable-rate quantisation defining a variable resolution. For this purpose an impulsion dictionary comprises: for a given dimension, increasing resolution dictionaries imbricated into each other and, for a given dimension, a union of: a totality (D'i&#x3c;N&#x3e;) of code-vectors produced, by inserting elements taken in a final set (A) into smaller dimension code-vectors according to a final set of predetermined insertion rules (F) and a second totality of code-vectors (Y&#x2032;) which are not obtainable by insertion into the smaller dimension code vectors according to said set of the insertion rules.

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Tregastel, France

Claude Lamblin